Journal articles on the topic 'Eutherians'
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1
Zhang, Xuzhe, Mihaela Pavlicev, Helen N. Jones, and Louis J. Muglia. "Eutherian-Specific Gene TRIML2 Attenuates Inflammation in the Evolution of Placentation." Molecular Biology and Evolution 37, no. 2 (October 9, 2019): 507–23. http://dx.doi.org/10.1093/molbev/msz238.
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Abstract Evolution of highly invasive placentation in the stem lineage of eutherians and subsequent extension of pregnancy set eutherians apart from other mammals, that is, marsupials with short-lived placentas, and oviparous monotremes. Recent studies suggest that eutherian implantation evolved from marsupial attachment reaction, an inflammatory process induced by the direct contact of fetal placenta with maternal endometrium after the breakdown of the shell coat, and shortly before the onset of parturition. Unique to eutherians, a dramatic downregulation of inflammation after implantation prevents the onset of premature parturition, and is critical for the maintenance of gestation. This downregulation likely involved evolutionary changes on maternal as well as fetal/placental side. Tripartite-motif family-like2 (TRIML2) only exists in eutherian genomes and shows preferential expression in preimplantation embryos, and trophoblast-derived structures, such as chorion and placental disc. Comparative genomic evidence supports that TRIML2 originated from a gene duplication event in the stem lineage of Eutheria that also gave rise to eutherian TRIML1. Compared with TRIML1, TRIML2 lost the catalytic RING domain of E3 ligase. However, only TRIML2 is induced in human choriocarcinoma cell line JEG3 with poly(I:C) treatment to simulate inflammation during viral infection. Its knockdown increases the production of proinflammatory cytokines and reduces trophoblast survival during poly(I:C) stimulation, while its overexpression reduces proinflammatory cytokine production, supporting TRIML2’s role as a regulatory inhibitor of the inflammatory pathways in trophoblasts. TRIML2’s potential virus-interacting PRY/SPRY domain shows significant signature of selection, suggesting its contribution to the evolution of eutherian-specific inflammation regulation during placentation.
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V.R. Prasad, Guntupalli, Omkar Verma, Ashok Sahni, and Ashu Khosla. "Cretaceous mammals of India–Stratigraphic distribution, diversity and intercontinental affinities." Journal of Palaeosciences 70, no. (1-2) (September 10, 2021): 173–92. http://dx.doi.org/10.54991/jop.2021.14.
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Extensive research carried out on the Cretaceous deposits of Laurasia has revealed an overwhelming presence of eutherian, metatherian and multituberculate groups of mammals in the Cretaceous ecosystems of Northern Hemisphere continents. In contrast, the relatively poorly documented fossil record of Cretaceous mammals from Gondwanan continents is represented by gondwanatherians, dryolestoids, and a few multituberculates and haramiyidans. Until now, no undoubted eutherian mammals have been reported from the Cretaceous strata of the southern continents except for India. In this context, Indian Cretaceous mammals assume great significance for understanding the origin and evolution of these mammals in Gondwana. Currently, the Cretaceous mammals of India include three groups, viz., eutherians, gondwanatherians, and haramiyidans. These three mammalian groups were recovered primarily from the Upper Cretaceous Deccan infra–and inter–trappean beds of peninsular India exposed near Bacharam, Naskal and Rangapur (Telengana), Upparhatti (Karnataka) and Kisalpuri (Madhya Pradesh) villages. Eutheria is by far the most diverse clade comprising three named genera (Deccanolestes, Sahnitherium, Kharmerungulatum) and one unnamed taxon (Eutheria incertae sedis). The gondwanatherians are known by Bharattherium bonapartei and Sudamericidae gen. et sp. indet. The third mammalian group, a possible haramiyidan, is represented by a solitary species Avashishta bacharamensis. Overall, the Cretaceous mammal fauna of India presents a complex biogeographic history with eutherians of Laurasian affinity, pan–Gondwanan gondwanatherians and a possible late surviving haramiyidan. Numerically abundant and speciose Deccanolestes, identified as an adapisoriculid, has been interpreted to have had originated in northward drifting Indian Plate in the Late Cretaceous and dispersed out of India into Africa and Europe over island arc systems (Oman–Kohistan–Dras) and the Ladakh magmatic arc at or near the Cretaceous–Paleogene boundary. A similar dispersal mode has also been visualized for Kharmerungulatum and Eutheria incertae sedis of Laurasian affinities.
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Dos Santos, Sandra E., Jairo Porfirio, Felipe B. da Cunha, Paul R. Manger, William Tavares, Leila Pessoa, Mary Ann Raghanti, Chet C. Sherwood, and Suzana Herculano-Houzel. "Cellular Scaling Rules for the Brains of Marsupials: Not as “Primitive” as Expected." Brain, Behavior and Evolution 89, no. 1 (2017): 48–63. http://dx.doi.org/10.1159/000452856.
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In the effort to understand the evolution of mammalian brains, we have found that common relationships between brain structure mass and numbers of nonneuronal (glial and vascular) cells apply across eutherian mammals, but brain structure mass scales differently with numbers of neurons across structures and across primate and nonprimate clades. This suggests that the ancestral scaling rules for mammalian brains are those shared by extant nonprimate eutherians - but do these scaling relationships apply to marsupials, a sister group to eutherians that diverged early in mammalian evolution? Here we examine the cellular composition of the brains of 10 species of marsupials. We show that brain structure mass scales with numbers of nonneuronal cells, and numbers of cerebellar neurons scale with numbers of cerebral cortical neurons, comparable to what we have found in eutherians. These shared scaling relationships are therefore indicative of mechanisms that have been conserved since the first therians. In contrast, while marsupials share with nonprimate eutherians the scaling of cerebral cortex mass with number of neurons, their cerebella have more neurons than nonprimate eutherian cerebella of a similar mass, and their rest of brain has fewer neurons than eutherian structures of a similar mass. Moreover, Australasian marsupials exhibit ratios of neurons in the cerebral cortex and cerebellum over the rest of the brain, comparable to artiodactyls and primates. Our results suggest that Australasian marsupials have diverged from the ancestral Theria neuronal scaling rules, and support the suggestion that the scaling of average neuronal cell size with increasing numbers of neurons varies in evolution independently of the allocation of neurons across structures.
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Goswami, Anjali, Nick Milne, and Stephen Wroe. "Biting through constraints: cranial morphology, disparity and convergence across living and fossil carnivorous mammals." Proceedings of the Royal Society B: Biological Sciences 278, no. 1713 (November 24, 2010): 1831–39. http://dx.doi.org/10.1098/rspb.2010.2031.
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Carnivory has evolved independently several times in eutherian (including placental) and metatherian (including marsupial) mammals. We used geometric morphometrics to assess convergences associated with the evolution of carnivory across a broad suite of mammals, including the eutherian clades Carnivora and Creodonta and the metatherian clades Thylacoleonidae, Dasyuromorphia, Didelphidae and Borhyaenoidea. We further quantified cranial disparity across eutherians and metatherians to test the hypothesis that the marsupial mode of reproduction has constrained their morphological evolution. This study, to our knowledge the first to extensively sample pre-Pleistocene taxa, analysed 30 three-dimensional landmarks, focused mainly on the facial region, which were digitized on 130 specimens, including 36 fossil taxa. Data were analysed with principal components (PC) analysis, and three measures of disparity were compared between eutherians and metatherians. PC1 showed a shift from short to long faces and seemed to represent diet and ecology. PC2 was dominated by the unique features of sabre-toothed forms: dramatic expansion of the maxilla at the expense of the frontal bones. PC3, in combination with PC1, distinguished metatherians and eutherians. Metatherians, despite common comparisons with felids, were more similar to caniforms, which was unexpected for taxa such as the sabre-toothed marsupial Thylacosmilus . Contrary to previous studies, metatherian carnivores consistently exhibited disparity which exceeded that of the much more speciose eutherian carnivore radiations, refuting the hypothesis that developmental constraints have limited the morphological evolution of the marsupial cranium.
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Collet, C., R. Joseph, and K. Nicholas. "Cloning, cDNA analysis and prolactin-dependent expression of a marsupial alpha-lactalbumin." Reproduction, Fertility and Development 2, no. 6 (1990): 693. http://dx.doi.org/10.1071/rd9900693.
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The gene for alpha-lactalbumin has been cloned from a tammar wallaby (Macropus eugenii) mammary gland cDNA library. Tammar alpha-lactalbumin has approximately 50 and 30% homology to the alpha-lactalbumins of eutherians at the levels of nucleotide and protein sequence respectively. Comparison of the inferred tammar polypeptide sequence with the sequence of the eutherian proteins reveals extensive divergence at almost all of the non-essential amino acid residues. However, the hydropathy plots of the tammar protein are almost identical to those of eutherian alpha-lactalbumins, suggesting that protein conformation is conserved. The tammar gene encodes a transcript of approximately 975 bases. Northern blot analysis of hormone-stimulated mammary gland explants shows that maximal induction of alpha-lactalbumin mRNA is dependent on prolactin and that expression is not modulated by other hormones that play a role in the initiation of lactation in eutherians.
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McKenzie, LM, and DW Cooper. "Low MHC class II variability in a marsupial." Reproduction, Fertility and Development 6, no. 6 (1994): 721. http://dx.doi.org/10.1071/rd9940721.
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The major histocompatibility complex (MHC) loci have been shown to be highly polymorphic in most eutherian ('placental') species studied. Several hypotheses have been advanced for the maintenance of this exceptional level of genetic variation, one of which suggests that it is necessary for successful eutherian reproduction. Marsupials (metatherians) and eutherians are the only two groups of viviparous mammals, but their modes of reproduction are quite distinct. Although marsupials have placentae, they are generally shorter lived and less invasive than in eutherians. Other investigations have shown that genetic variation at marsupial MHC class I loci is probably high. Weak or non-existent mixed lymphocyte culture responses previously reported in several marsupial species have suggested a lack of class II variation. Data have therefore been collected on the level of restriction fragment length polymorphism at MHC class II beta-chain encoding loci of a marsupial, Macropus eugenii (the tammar wallaby). This level is shown to be low, between the level of MHC variation found in cheetahs and a population of lions with a restricted genetic base. Attention is drawn to the need to collect more data on the level of class II variability in both eutherians and marsupials, and to the potential of marsupials for understanding the relation, if any, between mode of reproduction and MHC variability.
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Gerkema, Menno P., Wayne I. L. Davies, Russell G. Foster, Michael Menaker, and Roelof A. Hut. "The nocturnal bottleneck and the evolution of activity patterns in mammals." Proceedings of the Royal Society B: Biological Sciences 280, no. 1765 (August 22, 2013): 20130508. http://dx.doi.org/10.1098/rspb.2013.0508.
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In 1942, Walls described the concept of a ‘nocturnal bottleneck’ in placental mammals, where these species could survive only by avoiding daytime activity during times in which dinosaurs were the dominant taxon. Walls based this concept of a longer episode of nocturnality in early eutherian mammals by comparing the visual systems of reptiles, birds and all three extant taxa of the mammalian lineage, namely the monotremes, marsupials (now included in the metatherians) and placentals (included in the eutherians). This review describes the status of what has become known as the nocturnal bottleneck hypothesis, giving an overview of the chronobiological patterns of activity. We review the ecological plausibility that the activity patterns of (early) eutherian mammals were restricted to the night, based on arguments relating to endothermia, energy balance, foraging and predation, taking into account recent palaeontological information. We also assess genes, relating to light detection (visual and non-visual systems) and the photolyase DNA protection system that were lost in the eutherian mammalian lineage. Our conclusion presently is that arguments in favour of the nocturnal bottleneck hypothesis in eutherians prevail.
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Edwards, Carol A., Nozomi Takahashi, Jennifer A. Corish, and Anne C. Ferguson-Smith. "The origins of genomic imprinting in mammals." Reproduction, Fertility and Development 31, no. 7 (2019): 1203. http://dx.doi.org/10.1071/rd18176.
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Genomic imprinting is a process that causes genes to be expressed according to their parental origin. Imprinting appears to have evolved gradually in two of the three mammalian subclasses, with no imprinted genes yet identified in prototheria and only six found to be imprinted in marsupials to date. By interrogating the genomes of eutherian suborders, we determine that imprinting evolved at the majority of eutherian specific genes before the eutherian radiation. Theories considering the evolution of imprinting often relate to resource allocation and recently consider maternal–offspring interactions more generally, which, in marsupials, places a greater emphasis on lactation. In eutherians, the imprint memory is retained at least in part by zinc finger protein 57 (ZFP57), a Kruppel associated box (KRAB) zinc finger protein that binds specifically to methylated imprinting control regions. Some imprints are less dependent on ZFP57invivo and it may be no coincidence that these are the imprints that are found in marsupials. Because marsupials lack ZFP57, this suggests another more ancestral protein evolved to regulate imprints in non-eutherian subclasses, and contributes to imprinting control in eutherians. Hence, understanding the mechanisms acting at imprinting control regions across mammals has the potential to provide valuable insights into our understanding of the origins and evolution of genomic imprinting.
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Frankenberg, S., A. J. Pask, and M. B. Renfree. "259. Pluripotency genes in a marsupial, the tammar wallaby." Reproduction, Fertility and Development 20, no. 9 (2008): 59. http://dx.doi.org/10.1071/srb08abs259.
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Markers of pluripotency and early differentiation in the early embryo have been extensively characterised in eutherian species, most notably the mouse. By comparison, mechanisms controlling pluripotency and early lineage specification have received surprisingly little attention in marsupials, which represent the second major infraclass of mammals. Early marsupial embryogenesis exhibits overt morphological differences to that of eutherians, however the underlying developmental mechanisms may be conserved. In order to characterise early marsupial development at the molecular level, we have identified, cloned and analysed expression of orthologueues of several eutherian genes encoding transcription factors and signalling molecules involved in regulating pluripotency and early lineage specification. These genes include POU5F1 (OCT4), SOX2, NANOG, FGF4, FGFR2, CDX2, EOMES, TEAD4, GATA6 and KITL and are all expressed at early stages of development in the tammar. In addition, we have identified and cloned tammar POU2, which has orthologueues in non-mammalian vertebrates. POU2 is a paralogue of POU5F1 – a master regulator of pluripotency in eutherians. Genomic analysis indicates that POU5F1 arose via gene duplication of POU2 before the monotreme-therian divergence. Both genes have persisted in marsupials and monotremes, while POU2 was lost early during eutherian evolution. Similar expression profiles of tammar POU5F1 and POU2 in early embryos and gonadal tissues suggest possible overlapping roles in the maintenance of pluripotency.
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Messer, M., D. C. Shaw, A. S. Weiss, P. Rissmiller, and M. Griffiths. "Estimation of Divergence Dates for Monotremes From Comparisons of A-Lactalbumin Amino Acid Sequences." Australian Mammalogy 20, no. 2 (1998): 310. http://dx.doi.org/10.1071/am98323.
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cx-Lactalbumins were isolated from milk of the platypus (Ornithorhynchus anatinus) and the echidna (Tachyglossus aculeatus). Their amino acid sequences were determined and compared with those of the cx- lactalbumins often eutherian and two marsupial species, using the computer programme ("Distances") to calculate the number of differences (substitutions) between a total of 36 pairs of cx-lactalbumins. As expected, the amino acid sequences of the monotreme cx-lactalbumins were more similar to each other than to those of other mammals, as were the sequences of the marsupial and the eutherian cx-lactalbumins. If one makes the common assumption that marsupials and eutherians diverged from each other 135 Myr ago then simple calculations from the data would suggest that the platypus and echidna lineages diverged 56 ± 8 (SD) Myr ago and that monotremes diverged from the other mammals 152 ± 29 Myr ago. These values are not inconsistent with the little that is known about the palaeontology of the monotremes and are very similar to those derived from previous studies on globin sequences. If, however, monotreme cx-lactalbumins evolved more slowly than the cx-lactalbumins of eutherians and marsupials, these dates could be underestimates.
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Bartkowska, Katarzyna, Beata Tepper, Krzysztof Turlejski, and Ruzanna Djavadian. "Postnatal and Adult Neurogenesis in Mammals, Including Marsupials." Cells 11, no. 17 (September 1, 2022): 2735. http://dx.doi.org/10.3390/cells11172735.
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In mammals, neurogenesis occurs during both embryonic and postnatal development. In eutherians, most brain structures develop embryonically; conversely, in marsupials, a number of brain structures develop after birth. The exception is the generation of granule cells in the dentate gyrus, olfactory bulb, and cerebellum of eutherian species. The formation of these structures starts during embryogenesis and continues postnatally. In both eutherians and marsupials, neurogenesis continues in the subventricular zone of the lateral ventricle (SVZ) and the dentate gyrus of the hippocampal formation throughout life. The majority of proliferated cells from the SVZ migrate to the olfactory bulb, whereas, in the dentate gyrus, cells reside within this structure after division and differentiation into neurons. A key aim of this review is to evaluate advances in understanding developmental neurogenesis that occurs postnatally in both marsupials and eutherians, with a particular emphasis on the generation of granule cells during the formation of the olfactory bulb, dentate gyrus, and cerebellum. We debate the significance of immature neurons in the piriform cortex of young mammals. We also synthesize the knowledge of adult neurogenesis in the olfactory bulb and the dentate gyrus of marsupials by considering whether adult-born neurons are essential for the functioning of a given area.
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Singh, Devika, Dan Sun, Andrew G. King, David E. Alquezar-Planas, Rebecca N. Johnson, David Alvarez-Ponce, and Soojin V. Yi. "Koala methylomes reveal divergent and conserved DNA methylation signatures of X chromosome regulation." Proceedings of the Royal Society B: Biological Sciences 288, no. 1945 (February 24, 2021): 20202244. http://dx.doi.org/10.1098/rspb.2020.2244.
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X chromosome inactivation (XCI) mediated by differential DNA methylation between sexes is an iconic example of epigenetic regulation. Although XCI is shared between eutherians and marsupials, the role of DNA methylation in marsupial XCI remains contested. Here, we examine genome-wide signatures of DNA methylation across fives tissues from a male and female koala ( Phascolarctos cinereus ), and present the first whole-genome, multi-tissue marsupial ‘methylome atlas’. Using these novel data, we elucidate divergent versus common features of representative marsupial and eutherian DNA methylation. First, tissue-specific differential DNA methylation in koalas primarily occurs in gene bodies. Second, females show significant global reduction (hypomethylation) of X chromosome DNA methylation compared to males. We show that this pattern is also observed in eutherians. Third, on average, promoter DNA methylation shows little difference between male and female koala X chromosomes, a pattern distinct from that of eutherians. Fourth, the sex-specific DNA methylation landscape upstream of Rsx , the primary lnc RNA associated with marsupial XCI, is consistent with the epigenetic regulation of female-specific (and presumably inactive X chromosome-specific) expression. Finally, we use the prominent female X chromosome hypomethylation and classify 98 previously unplaced scaffolds as X-linked, contributing an additional 14.6 Mb (21.5%) to genomic data annotated as the koala X chromosome. Our work demonstrates evolutionarily divergent pathways leading to functionally conserved patterns of XCI in two deep branches of mammals.
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Hansen, Victoria L., and Robert D. Miller. "Transcription of immune genes at the fetomaternal interface during pregnancy in a model marsupial, Monodelphis domestica." Journal of Immunology 198, no. 1_Supplement (May 1, 2017): 226.20. http://dx.doi.org/10.4049/jimmunol.198.supp.226.20.
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Abstract The evolutionary challenge of nourishing an allogeneic conceptus in the presence of an adaptive immune system has intrigued immunologists since Sir Peter Medawar brought attention to the “fetal allograft problem” in the 1950s. Though much has been learned in reproductive immunology, it has largely been limited to eutherian mammals such as humans, mice, and mammalian livestock. Therians are the lineage of mammals that include both eutherians, or “placentals”, and marsupials. Though eutherians and marsupials diverged approximately 148 million years ago, the two lineages share a common viviparous ancestor. Therefore marsupials and eutherians likely share immunological traits during pregnancy. Previous RNA-Seq studies demonstrated increased transcription of immune genes in late, terminal pregnancy. However since the RNA-Seq data only represented one pregnancy time point, less than 24 hours until birth, it was unclear whether immune gene transcription should be attributed to pregnancy, implantation, or parturition. We expanded time points to target the last 144 hours of pregnancy during which both implantation and parturition occur in Monodelphis domestica. We examined the transcription of cytokines as well as complement and their regulators at the fetomaternal interface in pregnant opossums. We found a significant increase in transcription of cytokines in the last 24 hours of pregnancy and comparatively little transcription of cytokines at the time of implantation. There was also little transcription of some complement components throughout pregnancy, particularly those in the upstream cascade. Some downstream complement components trended toward increased transcription in the last 48 hours of pregnancy.
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Carter, Anthony M. "Recent advances in understanding evolution of the placenta: insights from transcriptomics." F1000Research 7 (January 19, 2018): 89. http://dx.doi.org/10.12688/f1000research.13115.1.
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The mammalian placenta shows an extraordinary degree of variation in gross and fine structure, but this has been difficult to interpret in physiological terms. Transcriptomics offers a path to understanding how structure relates to function. This essay examines how studies of gene transcription can inform us about placental evolution in eutherian and marsupial mammals and more broadly about convergent evolution of viviparity and placentation in vertebrates. Thus far, the focus has been on the chorioallantoic placenta of eutherians at term, the reproductive strategies of eutherians and marsupials, and the decidual response of the uterus at implantation. Future work should address gene expression during early stages of placental development and endeavor to cover all major groups of mammals. Comparative studies across oviparous and viviparous vertebrates have centered on the chorioallantoic membrane and yolk sac. They point to the possibility of defining a set of genes that can be recruited to support commonalities in reproductive strategies. Further advances can be anticipated from single-cell transcriptomics if those techniques are applied to a range of placental structures and in species other than humans and mice.
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L Bryant, S., and RW Rose. "Effect of Cadmium on the Reproductive Organs of the Male Potoroo Potorous tridactylus (Macropodidae)." Australian Journal of Biological Sciences 38, no. 3 (1985): 305. http://dx.doi.org/10.1071/bi9850305.
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Low (2' 28 mglkg) or high (4' 56 mg/kg) doses of cadmium chloride were administered, either intraperitoneally or subcutaneously, to adult male potoroos (P. tridactylus). After 7 days, the testes, caput epididymis and spermatic cords of the high-dose groups all displayed a degree of cellular damage; however, the damage was not as extensive as that which occurs in some eutherian species after only 24 h. This time differential might be attributed to structural differences between the testicular blood supply in eutherians and marsupials.
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Huttley, Gavin. "Do genomic datasets resolve the correct relationship among the placental, marsupial and monotreme lineages?" Australian Journal of Zoology 57, no. 4 (2009): 167. http://dx.doi.org/10.1071/zo09049.
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Did the mammal radiation arise through initial divergence of prototherians from a common ancestor of metatherians and eutherians, the Theria hypothesis, or of eutherians from a common ancestor of metatherians and prototherians, the Marsupionta hypothesis? Molecular phylogenetic analyses of point substitutions applied to this problem have been contradictory – mtDNA-encoded sequences supported Marsupionta, nuclear-encoded sequences and RY (purine–pyrimidine)-recoded mtDNA supported Theria. The consistency property of maximum likelihood guarantees convergence on the true tree only with longer alignments. Results from analyses of genome datasets should therefore be impervious to choice of outgroup. We assessed whether important hypotheses concerning mammal evolution, including Theria/Marsupionta and the branching order of rodents, carnivorans and primates, are resolved by phylogenetic analyses using ~2.3 megabases of protein-coding sequence from genome projects. In each case, only two tree topologies were being compared and thus inconsistency in resolved topologies can only derive from flawed models of sequence divergence. The results from all substitution models strongly supported Theria. For the eutherian lineages, all models were sensitive to the outgroup. We argue that phylogenetic inference from point substitutions will remain unreliable until substitution models that better match biological mechanisms of sequence divergence have been developed.
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Suárez, Rodrigo, Annalisa Paolino, Laura R. Fenlon, Laura R. Morcom, Peter Kozulin, Nyoman D. Kurniawan, and Linda J. Richards. "A pan-mammalian map of interhemispheric brain connections predates the evolution of the corpus callosum." Proceedings of the National Academy of Sciences 115, no. 38 (September 4, 2018): 9622–27. http://dx.doi.org/10.1073/pnas.1808262115.
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The brain of mammals differs from that of all other vertebrates, in having a six-layered neocortex that is extensively interconnected within and between hemispheres. Interhemispheric connections are conveyed through the anterior commissure in egg-laying monotremes and marsupials, whereas eutherians evolved a separate commissural tract, the corpus callosum. Although the pattern of interhemispheric connectivity via the corpus callosum is broadly shared across eutherian species, it is not known whether this pattern arose as a consequence of callosal evolution or instead corresponds to a more ancient feature of mammalian brain organization. Here we show that, despite cortical axons using an ancestral commissural route, monotremes and marsupials share features of interhemispheric connectivity with eutherians that likely predate the origin of the corpus callosum. Based on ex vivo magnetic resonance imaging and tractography, we found that connections through the anterior commissure in both fat-tailed dunnarts (Marsupialia) and duck-billed platypus (Monotremata) are spatially segregated according to cortical area topography. Moreover, cell-resolution retrograde and anterograde interhemispheric circuit mapping in dunnarts revealed several features shared with callosal circuits of eutherians. These include the layered organization of commissural neurons and terminals, a broad map of connections between similar (homotopic) regions of each hemisphere, and regions connected to different areas (heterotopic), including hyperconnected hubs along the medial and lateral borders of the cortex, such as the cingulate/motor cortex and claustrum/insula. We therefore propose that an interhemispheric connectome originated in early mammalian ancestors, predating the evolution of the corpus callosum. Because these features have been conserved throughout mammalian evolution, they likely represent key aspects of neocortical organization.
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Nagy, KA. "Field Bioenergetics of Mammals - What Determines Field Metabolic Rates." Australian Journal of Zoology 42, no. 1 (1994): 43. http://dx.doi.org/10.1071/zo9940043.
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Field metabolic rates (FMRs) of 61 species of mammals, as measured with doubly labelled water, range from 29 kJ day-1 (0.34 W) in pipistrel bats to 49 MJ day-1 (570 W) in northern elephant seals, which is a range of 1678 times. Most of this variation is due to differences in body mass; the least-squares, log-log regression of mammalian FMR on body mass (kJ day-1 = 5.27 g0.723) has a coefficient of determination (r2) of 0.961, indicating that variation in log(body mass) accounts for 96% of variation in log(FMR). The scaling of FMR in marsupials (kJ day-1 = 10.83 g0.582, 17 species) differs significantly from that in eutherian mammals (kJ day-1 = 4.63 g0.762, 44 species), and the respective r2-values (0.978 and 0.972) indicate that these taxonomic infraclasses explain another 1% of variation in log(FMR). After adjusting for mass and infraclass effects, residual variation is still substantial (2.5-fold among marsupials and 6-fold among eutherians). What accounts for this variation? Neither taxonomic order (or family within the Marsupialia), diet category (e.g. herbivore, camivore), nor habitat (e.g. marine, tundra) explained much residual variation, except that desert-dwelling eutherians had significantly lower FMRs than expected for eutherians of their mass. The failure of taxonomic and ecological categories to account for residual variation may be due, in part, to small sample sizes and skewed distributions of these categories along the mass axis, but it seems likely that other sources of variation, such as season, sex, age, ambient temperature, daily behaviour pattern and food availability may have large effects on FMR that are not accounted for in this analysis.
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Gemmell, RT. "A comparative study of the corpus luteum." Reproduction, Fertility and Development 7, no. 3 (1995): 303. http://dx.doi.org/10.1071/rd9950303.
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The corpus luteum (CL) is a transitory organ which has a regulatory role in reproduction. Sharks, amphibians and reptiles have corpora lutea that produce progesterone which influences the rate of embryonic development. The egg-laying monotremes and the two major mammalian groups, eutherian and marsupial, have a CL that secretes progesterone. Most eutherians have allowed for the uterine development of their young by extending the length of the oestrous cycle and the CL or placenta actively secretes progesterone until birth. Gestation in the marsupial does not extend beyond the length of an oestrous cycle and the major part of fetal development takes place in the pouch. Where the extension of the post-luteal phase in the eutherian has allowed for the uterine development of young, the marsupial has extended the pre-luteal phase of the oestrous cycle and has evolved an alternative reproductive strategy, embryonic diapause. The mechanism for the secretion of hormones from the CL has been controversial for many years. Densely-staining secretory granules have been observed in the CL of sharks, marsupials and eutherians. These granules have been reported to contain relaxin, oxytocin or mesotocin, and progesterone. A hypothesis to suit all available data is that all hormones secreted by the CL are transported within such granules. In conclusion, although there are obvious differences in the mode of reproduction in the two main mammalian groups, it is apparent that there is a great deal of similarity in the hormonal control of regression of the CL and parturition.
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Cruz, Y. P., H. Morton, A. C. Cavanagh, L. Selwood, S. D. Wilson, and M. Sasaki. "Early pregnancy factor in marsupials." Australian Journal of Zoology 54, no. 3 (2006): 211. http://dx.doi.org/10.1071/zo05050.
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Maternal recognition of pregnancy in marsupials occurs in more subtle ways than it does in eutherians. For instance, unlike in eutherians, the plasma progesterone profiles of pregnant and non-pregnant animals are similar during the luteal phase. It is typically during the brief luteal phase that both gestation and parturition occur in marsupials. Yet histological and physiological changes have been documented between gravid and non-gravid uteri in certain monovular marsupials and between pregnant and non-pregnant animals in polyovular marsupials. Early pregnancy factor (EPF), a 10.8-kDa serum protein known to be homologous to chaperonin 10, is associated with maternal immunosuppression, embryonic development and pregnancy in eutherian mammals. It has been reported in two Australian marsupials: the dasyurid Sminthopsis macroura and the phalangerid Trichosurus vulpecula. This paper documents its occurrence in the New World didelphid Monodelphis domestica. EPF is detectable by rosette inhibition assay in the peripheral circulation of pregnant but not of non-pregnant or pseudopregnant animals. Our work focuses on the embryo–maternal signalling role of EPF during pregnancy. Because progesterone-driven changes are similar in pregnant and non-pregnant marsupials, these animals are an excellent laboratory model in which to investigate the role of EPF in orchestrating the physiological changes necessary to sustain pregnancy.
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Royall, Amy H., Stephen Frankenberg, Andrew J. Pask, and Peter W. H. Holland. "Of eyes and embryos: subfunctionalization of the CRX homeobox gene in mammalian evolution." Proceedings of the Royal Society B: Biological Sciences 286, no. 1907 (July 24, 2019): 20190830. http://dx.doi.org/10.1098/rspb.2019.0830.
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ETCHbox genes are fast-evolving homeobox genes present only in eutherian (placental) mammals which originated by duplication and divergence from a conserved homeobox gene, Cone-rod homeobox ( CRX ). While expression and function of CRX are restricted to the retina in eutherian mammals, ETCHbox gene expression is specific to preimplantation embryos. This dramatic difference could reflect the acquisition of new functions by duplicated genes or subfunctionalization of pleiotropic roles between CRX and ETCHbox genes. To resolve between these hypotheses, we compared expression, sequence and inferred function between CRX of metatherian (marsupial) mammals and ETCHbox genes of eutherians. We find the metatherian CRX homeobox gene is expressed in early embryos and in eyes, unlike eutherian CRX , and distinct amino acid substitutions were fixed in the metatherian and eutherian evolutionary lineages consistent with altered transcription factor specificity. We find that metatherian CRX is capable of regulating embryonically expressed genes in cultured cells in a comparable way to eutherian ETCHbox. The data are consistent with CRX having a dual role in eyes and embryos of metatherians, providing an early embryonic function comparable to that of eutherian ETCHbox genes; we propose that subfunctionalization of pleiotropic functions occurred after gene duplication along the placental lineage, followed by functional elaboration.
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Godinot, M., and G. V. R. Prasad. "Discovery of cretaceous arboreal eutherians." Naturwissenschaften 81, no. 2 (February 1994): 79–81. http://dx.doi.org/10.1007/bf01138464.
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Godinot, M., and G. V. R. Prasad. "Discovery of Cretaceous Arboreal Eutherians." Naturwissenschaften 81, no. 2 (February 1, 1994): 79–81. http://dx.doi.org/10.1007/s001140050033.
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Crawford, J. L., D. A. Heath, L. J. Haydon, B. P. Thomson, and D. C. Eckery. "Gene expression and secretion of LH and FSH in relation to gene expression of GnRH receptors in the brushtail possum (Trichosurus vulpecula) demonstrates highly conserved mechanisms." REPRODUCTION 137, no. 1 (January 2009): 129–40. http://dx.doi.org/10.1530/rep-08-0347.
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In eutherian mammals, the gonadotrophins (LH and FSH) are synthesized and stored in gonadotroph cells under the regulation of multiple mechanisms including GnRH. Very little is known about the regulation of gonadotrophin secretion and storage in pituitary glands of marsupials. This study revealed, using quantitative PCR and heterologous RIA techniques, thatLHBmRNA expression levels remained constant over the oestrous cycle, regardless of the presence of a preovulatory LH surge, which is characteristic of a hormone secreted under regulation. Our sampling regime was unable to detect pulses of LH during the follicular phase, althoughGNRHRmRNA levels had increased at this time. Pulses of LH were, however, detected in the luteal phase of cycling females, in anoestrus females and in males. There was a positive correlation between gene expression ofFSHBand plasma levels of FSH at different stages of the oestrous cycle and no pulses of FSH were detected at any time; all characteristics of a hormone secreted via the constitutive pathway. Usingin situhybridisation and immunohistochemistry methods, we determined that mRNA expression ofLHBandFSHB, and protein storage of gonadotrophins exhibited a similar pattern of localisation within the pituitary gland. Additionally, sexual dimorphism of gonadotroph populations was evident. In summary, these findings are similar to that reported in eutherians and considering that marsupial evolution diverged from eutherians over 100 million years ago suggests that the regulation of gonadotrophins is highly conserved indeed.
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Shah, SKH, SC Nicol, and R. Swain. "Functional-Morphology of the Cranial Vasculature and the Nasal Passage in the Tasmanian Devil, Sarcophilus-Harrisii (Marsupialia, Dasyuridae) - a Marsupial Carotid Rete." Australian Journal of Zoology 34, no. 2 (1986): 125. http://dx.doi.org/10.1071/zo9860125.
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An anatomical examination of the cranial vascular system of the Tasmanian devil, Sarcophilus harrisii (Boitard), using angiography, polyester resin casts, and dissections, demonstrated the presence of two bilateral retia analogous to the carotid retia of panting eutherians. Such structures have not previously been demonstrated in any marsupial. The pattern of the Circle of Willis differed from that reported for any eutherian. A possible role of the retia in cooling the cranial blood supply during thermal panting would be aided by the complex turbinate bone structure, which provides a large surface area for the nasal mucosa. The mucosa was observed to be highly vascularized, and a lateral nasal gland was found on the nasal septum.
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Jolly, SE, GA Morriss, S. Scobie, and PE Cowan. "Composition of Milk of the Common Brushtail Possum, Trichosurus Vulpecula (Marsupialia: Phalangeridae): Concentrations of Elements." Australian Journal of Zoology 44, no. 5 (1996): 479. http://dx.doi.org/10.1071/zo9960479.
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The concentrations of 11 elements (calcium, copper, iron, magnesium, manganese, phosphorus, potassium, sodium, strontium, sulphur and zinc) were measured in milk samples collected from 193 lactating brushtail possums, Trichosurus vulpecula, at all stages of lactation. Most elements showed patterns of change during lactation similar to those of other marsupials. The most marked changes occurred at about 80-120 days, when the growth rate of the pouch young increased and developmental changes took place, such as eye opening and fur growth. Compared with eutherians, copper and iron concentrations were high in possum milk, as in other marsupials, but zinc levels were exceptionally high. Strontium and manganese levels, not measured before in marsupial milk, were considerably higher than levels reported in eutherian milk. In contrast to eutherian mammals, marsupial young must be supplied with large quantities of minerals in the milk as almost all growth and development occurs after birth, and possum young are entirely dependent on milk supplied by the mother for about the first 100 days.
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Diaz, Jessica L., Verl B. Siththanandan, Victoria Lu, Nicole Gonzalez-Nava, Lincoln Pasquina, Jessica L. MacDonald, Mollie B. Woodworth, et al. "An evolutionarily acquired microRNA shapes development of mammalian cortical projections." Proceedings of the National Academy of Sciences 117, no. 46 (November 2, 2020): 29113–22. http://dx.doi.org/10.1073/pnas.2006700117.
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The corticospinal tract is unique to mammals and the corpus callosum is unique to placental mammals (eutherians). The emergence of these structures is thought to underpin the evolutionary acquisition of complex motor and cognitive skills. Corticospinal motor neurons (CSMN) and callosal projection neurons (CPN) are the archetypal projection neurons of the corticospinal tract and corpus callosum, respectively. Although a number of conserved transcriptional regulators of CSMN and CPN development have been identified in vertebrates, none are unique to mammals and most are coexpressed across multiple projection neuron subtypes. Here, we discover 17 CSMN-enriched microRNAs (miRNAs), 15 of which map to a single genomic cluster that is exclusive to eutherians. One of these, miR-409-3p, promotes CSMN subtype identity in part via repression of LMO4, a key transcriptional regulator of CPN development. In vivo, miR-409-3p is sufficient to convert deep-layer CPN into CSMN. This is a demonstration of an evolutionarily acquired miRNA in eutherians that refines cortical projection neuron subtype development. Our findings implicate miRNAs in the eutherians’ increase in neuronal subtype and projection diversity, the anatomic underpinnings of their complex behavior.
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Tojima, Sayaka, Hidaka Anetai, Kaito Koike, Saori Anetai, Kounosuke Tokita, Chris Leigh, and Jaliya Kumaratilake. "Gross anatomy of the gluteal and posterior thigh muscles in koalas based on their innervations." PLOS ONE 17, no. 9 (September 14, 2022): e0261805. http://dx.doi.org/10.1371/journal.pone.0261805.
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Morphological and functional comparison of convergently-evolved traits in marsupials and eutherians is an important aspect of studying adaptive divergence in mammals. However, the anatomy of marsupials has been particularly difficult to evaluate for multiple reasons. First, previous studies on marsupial anatomy are often uniformly old and non-exhaustive. Second, muscle identification was historically based on muscle attachment sites, but attachment sites have since been declared insufficient for muscle identification due to extensive interspecific variation. For example, different names have been used for muscles that are now thought to be equivalent among several different species, which causes confusion. Therefore, descriptions of marsupial muscles have been inconsistent among previous studies, and their anatomical knowledge itself needs updating. In this study, the koala was selected as the representative marsupial, in part because koala locomotion may comprise primate (eutherian)-like and marsupial-like mechanics, making it an interesting phylogenetic group for studying adaptive divergence in mammals. Gross dissection of the lower limb muscles (the gluteal and the posterior thigh regions) was performed to permit precise muscle identification. We first resolved discrepancies among previous studies by identifying muscles according to their innervation; this recent, more reliable technique is based on the ontogenetic origin of the muscle, and it allows for comparison with other taxa (i.e., eutherians). We compared our findings with those of other marsupials and arboreal primates and identified traits common to both arboreal primates and marsupials as well as muscle morphological features unique to koalas.
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Collet, C., R. Joseph, and K. Nicholas. "Molecular characterization and in-vitro hormonal requirements for expression of two casein genes from a marsupial." Journal of Molecular Endocrinology 8, no. 1 (February 1992): 13–20. http://dx.doi.org/10.1677/jme.0.0080013.
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ABSTRACT Two marsupial casein genes have been isolated from a tammar wallaby (Macropus eugenii) mammary gland cDNA library. Comparisons of the tammar α- and β-casein genes with their eutherian homologues reveal extensive divergence at the levels of nucleotide and amino acid sequences. Regions of similarity between the tammar and eutherian Ca2+-sensitive caseins are restricted to the major phosphorylation sites and the signal peptides. Quantification of casein mRNA levels in hormone-stimulated mammary gland explants from tammars in late pregnancy suggests that maximal induction of the β-casein gene is dependent upon prolactin and insulin, while maximal induction of the α-casein gene is dependent upon prolactin, insulin and cortisol. These results are in contrast to earlier studies which show that the maximal induction of a putative 19 kDa casein, α-lactalbumin and β-lactoglobulin in the tammar mammary gland is dependent upon prolactin alone. The expression of the latter three genes is not modulated by other hormones known to play a role in the in-vitro initiation of lactation in eutherians.
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Voyle, Roger B., Bryan P. Haines, Kelly A. Loffler, Rory M. Hope, Peter D. Rathjen, and William G. Breed. "Isolation and characterisation of zona pellucida A (ZPA) cDNAs from two species of marsupial: regulated oocyte-specific expression of ZPA transcripts." Zygote 7, no. 3 (August 1999): 239–48. http://dx.doi.org/10.1017/s0967199499000623.
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The zona pellucida (ZP) is an extracellular glycoprotein coat that is deposited around the oocyte during folliculogenesis and performs several functions that relate to fertilisation and preimplantion development. In eutherian mammals it consists of three major glycoproteins – ZPA, ZPB, and ZPC – but little is known about its molecular constitution in marsupials. We have isolated the cDNA encoding the ZPA homologue in two distantly related marsupial series: the possum, Trichosurus vulpecula (a phalangerid) and the dunnart Sminthopsis crassicaudata (a dasyurid). The two cDNA sequences were 86% identical and showed extensive regions of homology to eutherian ZPA proteins, particularly in the central region of the molecule. Many other features of the ZPA protein, except the positioning of the N-linked glycosylation sites, were also conserved between marsupials and eutherians. ZPA expression was shown to occur maximally in the cytoplasm of the oocyte primary follicles with a little, but significant, expression in oocytes of both primordial follicles and in the cytoplasm of the oocyte in follicles with an antral cavity. No expression was seen in surrounding follicle or granulosa cells
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Ong, Oselyne T. W., Lauren J. Young, and Julie M. Old. "Preliminary genomic survey and sequence analysis of the complement system in non-eutherian mammals." Australian Mammalogy 38, no. 1 (2016): 80. http://dx.doi.org/10.1071/am15036.
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The complement system is a major mediator of the vertebrate immune system, which functions in both innate and specific immune responses. It comprises more than 30 proteins working to remove foreign cells by way of anaphylatoxins, opsonins or the membrane attack complex. Over the last few years, whole genome sequences of non-eutherian mammals (marsupials and a monotreme), the gray short-tailed opossum (Monodelphis domestica), tammar wallaby (Macropus eugenii), Tasmanian devil (Sarcophilus harrisii), koala (Phascolarctos cinereus) and platypus (Ornithorhynchus anatinus), have become publicly available. Using these sequences, we have identified an array of complement components in non-eutherians using online search tools and algorithms. Of 57 complement and complement-related genes investigated, we identified 46 in the gray short-tailed opossum genome, 27 in the tammar wallaby genome, 44 in the Tasmanian devil genome, 47 in the koala genome and 40 in the platypus genome. The results of this study confirm the presence of key complement components in the immune repertoire of non-eutherian mammals and provide a platform for future studies on immune protection in young marsupials.
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Hinds, D. S., R. V. Baudinette, R. E. MacMillen, and E. A. Halpern. "Maximum metabolism and the aerobic factorial scope of endotherms." Journal of Experimental Biology 182, no. 1 (September 1, 1993): 41–56. http://dx.doi.org/10.1242/jeb.182.1.41.
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Minimum and maximum metabolism in response to cold were measured in 30 species of Australian monotremes, marsupials, eutherians and birds. In marsupials and the echidna, maximum metabolism was also determined during treadmill locomotion. These data were used to determine, for the first time, the relationships between maximum metabolism and body mass in the four endothermic groups and to compare aerobic factorial scopes (the ratio of maximum to minimum metabolism) elicited by cold and locomotion. The effect of body mass on maximum metabolism is the same in marsupials and eutherians (the therians) but is significantly less in birds. At the same body mass, there is no difference between the two therian groups for either minimum or maximum metabolism induced by either cold or locomotion. Aerobic scope during cold is significantly higher in marsupials (8.3) than in eutherians (5.1), birds (5.4) and monotremes (5.4). Aerobic scope during locomotion in all groups is almost twice that observed in cold conditions.
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Hao, Yue, Hyuk Jin Lee, Michael Baraboo, Katherine Burch, Taylor Maurer, Jason A. Somarelli, and Gavin C. Conant. "Baby Genomics: Tracing the Evolutionary Changes That Gave Rise to Placentation." Genome Biology and Evolution 12, no. 3 (February 13, 2020): 35–47. http://dx.doi.org/10.1093/gbe/evaa026.
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Abstract It has long been challenging to uncover the molecular mechanisms behind striking morphological innovations such as mammalian pregnancy. We studied the power of a robust comparative orthology pipeline based on gene synteny to address such problems. We inferred orthology relations between human genes and genes from each of 43 other vertebrate genomes, resulting in ∼18,000 orthologous pairs for each genome comparison. By identifying genes that first appear coincident with origin of the placental mammals, we hypothesized that we would define a subset of the genome enriched for genes that played a role in placental evolution. We thus pinpointed orthologs that appeared before and after the divergence of eutherian mammals from marsupials. Reinforcing previous work, we found instead that much of the genetic toolkit of mammalian pregnancy evolved through the repurposing of preexisting genes to new roles. These genes acquired regulatory controls for their novel roles from a group of regulatory genes, many of which did in fact originate at the appearance of the eutherians. Thus, orthologs appearing at the origin of the eutherians are enriched in functions such as transcriptional regulation by Krüppel-associated box-zinc-finger proteins, innate immune responses, keratinization, and the melanoma-associated antigen protein class. Because the cellular mechanisms of invasive placentae are similar to those of metastatic cancers, we then used our orthology inferences to explore the association between placenta invasion and cancer metastasis. Again echoing previous work, we find that genes that are phylogenetically older are more likely to be implicated in cancer development.
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Lefèvre, Christophe M., Julie A. Sharp, and Kevin R. Nicholas. "Characterisation of monotreme caseins reveals lineage-specific expansion of an ancestral casein locus in mammals." Reproduction, Fertility and Development 21, no. 8 (2009): 1015. http://dx.doi.org/10.1071/rd09083.
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Using a milk-cell cDNA sequencing approach we characterised milk-protein sequences from two monotreme species, platypus (Ornithorhynchus anatinus) and echidna (Tachyglossus aculeatus) and found a full set of caseins and casein variants. The genomic organisation of the platypus casein locus is compared with other mammalian genomes, including the marsupial opossum and several eutherians. Physical linkage of casein genes has been seen in the casein loci of all mammalian genomes examined and we confirm that this is also observed in platypus. However, we show that a recent duplication of β-casein occurred in the monotreme lineage, as opposed to more ancient duplications of α-casein in the eutherian lineage, while marsupials possess only single copies of α- and β-caseins. Despite this variability, the close proximity of the main α- and β-casein genes in an inverted tail–tail orientation and the relative orientation of the more distant kappa-casein genes are similar in all mammalian genome sequences so far available. Overall, the conservation of the genomic organisation of the caseins indicates the early, pre-monotreme development of the fundamental role of caseins during lactation. In contrast, the lineage-specific gene duplications that have occurred within the casein locus of monotremes and eutherians but not marsupials, which may have lost part of the ancestral casein locus, emphasises the independent selection on milk provision strategies to the young, most likely linked to different developmental strategies. The monotremes therefore provide insight into the ancestral drivers for lactation and how these have adapted in different lineages.
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Montellano-Ballesteros, Marisol, Richard C. Fox, and Craig S. Scott. "Species composition of the Late Cretaceous eutherian mammal Paranyctoides Fox." Canadian Journal of Earth Sciences 50, no. 7 (July 2013): 693–700. http://dx.doi.org/10.1139/cjes-2012-0184.
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Although the known record of Mesozoic eutherian mammals has been significantly enriched in recent years, early eutherian evolution is still not well understood. Among the more controversial of Mesozoic eutherians is Paranyctoides Fox, which was described in 1979 from the Judithian Dinosaur Park Formation, Alberta, Canada. It is a rare taxon and therefore has been identified in only a few other North American Late Cretaceous local faunas since. Within the past decade, dental and gnathic remains discovered in Central Asia have also been referred to Paranyctoides, thereby expanding the geographic range of the genus substantially and making it the only Late Cretaceous eutherian ostensibly occurring in both continents. As a result of our detailed study of Paranyctoides, however, we find that the Central Asian species lack the diagnostic characters of Paranyctoides and must be referred to other taxa. We conclude that this genus was limited to North America, ranging from Aquilan to Lancian time, and accordingly we recognize as valid only the following species: Paranyctoides sternbergi (Judithian, Alberta), P. maleficus (Aquilan, Alberta), Paranyctoides Wahweap sp. A and sp. B (Judithian, Utah), Paranyctoides Kaiparowits sp. A and sp. B (Judithian, Utah). Another purported species of Paranyctoides, P. megakeros, from the Lancian of Wyoming, is a junior synonym of Alostera saskatchewanensis.
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Raudsepp, Terje, and Bhanu P. Chowdhary. "The Eutherian Pseudoautosomal Region." Cytogenetic and Genome Research 147, no. 2-3 (2015): 81–94. http://dx.doi.org/10.1159/000443157.
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The pseudoautosomal region (PAR) is a unique segment of sequence homology between differentiated sex chromosomes where recombination occurs during meiosis. Molecular and functional properties of the PAR are distinctive from the autosomes and the remaining regions of the sex chromosomes. These include a higher rate of recombination than genome average, bias towards GC-substitutions and increased interindividual nucleotide divergence and mutations. As yet, the PAR has been physically demarcated in only 28 eutherian species representing 6 mammalian orders. Murid rodents have the smallest, gene-poorest and most diverged PARs. Other eutherian PARs are largely homologous but differ in size and gene content, being the smallest in equids and human/simian primates and much larger in other eutherians. Because pseudoautosomal genes escape X inactivation, their dosage changes with sex chromosome aneuploidies, whereas phenotypic effects of the latter depend on the size and gene content of the PAR. Thus, X monosomy is more viable in mice, humans and horses than in species with larger PARs. Presently, little is known about the functions of PAR genes in individual species, though human studies suggest their involvement in early embryonic development. The PAR is, thus, of evolutionary, genetic and biomedical significance and a ‘research hotspot' in eutherian genomes.
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Bakker, Anthony J., Ann L. Parkinson, and Stewart I. Head. "Contractile properties of single-skinned skeletal muscle fibres of the extensor digitorum longus muscle of the Australian short-nosed echidna." Australian Journal of Zoology 53, no. 4 (2005): 237. http://dx.doi.org/10.1071/zo05011.
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Eutherian mammal fast-twitch muscle fibres share similar contractile activation properties, suggesting that these properties are highly conserved in mammals. To investigate this hypothesis, we examined the contractile properties of skeletal muscle from the order Monotremata, a mammalian order that separated from eutherians 150 million years ago. The Ca2+- and Sr2+-activation properties of single mechanically skinned skeletal muscle fibres from the extensor digitorum longus (EDL) muscle of the short-nosed echidna were determined. Sigmoidal curves fitted to force response data plotted as a function of pCa (–log[Ca2+]), had a mean slope of 4.32 ± 0.28 and a mean pCa50 and pCa10 value of 6.18 ± 0.01 and 6.41 ± 0.02 respectively (n = 20). The mean pSr50, pSr10 and slope values of curves fitted to the force-response data after activation with Sr2+ were 4.80 ± 0.03, 5.29 ± 0.07 and 2.75 ± 0.18 respectively (n = 20). The mean pCa50–pSr50 value for the echidna EDL fibres was 1.37 ± 0.04. In five of the echidna fibres, exposure to submaximal Ca2+ concentrations produced myofibrillar force oscillations (mean frequency, 0.13 ± 0.01 Hz), a phenomenon found only in eutherian slow and intermediate muscle fibres. These results show that echidna EDL fibres generally have similar contractile properties to eutherian fast-twitch skeletal muscle fibres, such as those found in the EDL of the rat.
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Polymeropoulos, E. T., G. Heldmaier, P. B. Frappell, B. M. McAllan, K. W. Withers, M. Klingenspor, C. R. White, and M. Jastroch. "Phylogenetic differences of mammalian basal metabolic rate are not explained by mitochondrial basal proton leak." Proceedings of the Royal Society B: Biological Sciences 279, no. 1726 (June 2011): 185–93. http://dx.doi.org/10.1098/rspb.2011.0881.
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Metabolic rates of mammals presumably increased during the evolution of endothermy, but molecular and cellular mechanisms underlying basal metabolic rate (BMR) are still not understood. It has been established that mitochondrial basal proton leak contributes significantly to BMR. Comparative studies among a diversity of eutherian mammals showed that BMR correlates with body mass and proton leak. Here, we studied BMR and mitochondrial basal proton leak in liver of various marsupial species. Surprisingly, we found that the mitochondrial proton leak was greater in marsupials than in eutherians, although marsupials have lower BMRs. To verify our finding, we kept similar-sized individuals of a marsupial opossum ( Monodelphis domestica ) and a eutherian rodent ( Mesocricetus auratus ) species under identical conditions, and directly compared BMR and basal proton leak. We confirmed an approximately 40 per cent lower mass specific BMR in the opossum although its proton leak was significantly higher (approx. 60%). We demonstrate that the increase in BMR during eutherian evolution is not based on a general increase in the mitochondrial proton leak, although there is a similar allometric relationship of proton leak and BMR within mammalian groups. The difference in proton leak between endothermic groups may assist in elucidating distinct metabolic and habitat requirements that have evolved during mammalian divergence.
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Richardson, S. J., A. J. Bradley, W. Duan, R. E. Wettenhall, P. J. Harms, J. J. Babon, B. R. Southwell, S. Nicol, S. C. Donnellan, and G. Schreiber. "Evolution of marsupial and other vertebrate thyroxine-binding plasma proteins." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 266, no. 4 (April 1, 1994): R1359—R1370. http://dx.doi.org/10.1152/ajpregu.1994.266.4.r1359.
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Binding of radioactive thyroxine to proteins in the plasma of vertebrates was studied by electrophoresis followed by autoradiography. Albumin was found to be a thyroxine carrier in the blood of all studied fish, amphibians, reptiles, monotremes, marsupials, eutherians (placental mammals), and birds. Thyroxine binding to transthyretin was detected in the blood of eutherians, diprotodont marsupials, and birds, but not in blood from fish, toads, reptiles, monotremes, and Australian polyprotodont marsupials. Globulins binding thyroxine were only observed in the plasma of some mammals. Apparently, albumin is the phylogenetically oldest thyroxine carrier in vertebrate blood. Transthyretin gene expression in the liver developed in parallel, and independently, in the evolutionary lineages leading to eutherians, to diprotodont marsupials, and to birds. In contrast, high transthyretin mRNA levels, strong synthesis, and secretion of transthyretin in choroid plexus from reptiles and birds indicate that transthyretin gene expression in the choroid plexus evolved much earlier than in the liver, probably at the stage of the stem reptiles. NH2-terminal sequence analysis suggests a change of transthyretin pre-mRNA splicing during evolution.
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Collet, C., R. Joseph, and K. Nicholas. "A marsupial β-lactoglobulin gene: characterization and prolactin-dependent expression." Journal of Molecular Endocrinology 6, no. 1 (February 1991): 9–16. http://dx.doi.org/10.1677/jme.0.0060009.
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ABSTRACT Analysis of the tammar wallaby β-lactoglobulin cDNA and inferred amino acid sequences reveal extensive sequence divergence from the eutherian β-lactoglobulins. Conserved residues include the cysteines and a number of individual amino acids involved in structure and ligand-binding. The only region of extended similarity is a heptapeptide sequence which may impart specificity to its interaction with a receptor protein. Northern analysis of total mammary RNA revealed two transcripts which result from differential utilization of polyadenylation signals. The concentration of β-lactoglobulin mRNA increased in late lactation and correlates with increases in milk production and levels of milk fat. Quantification of β-lactoglobulin mRNA levels in hormone-stimulated mammary gland explants from tammars in late pregnancy suggests that maximal induction of the gene is dependent on prolactin alone and that expression is not modulated by other hormones known to play a role in the initiation of lactation in eutherians.
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Prasad, G. V. R., and M. Godinot. "Eutherian tarsal bones from the Late Cretaceous of India." Journal of Paleontology 68, no. 4 (July 1994): 892–902. http://dx.doi.org/10.1017/s0022336000026342.
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Eutherian tarsal bones of Late Cretaceous age are reported for the first time from sedimentary beds intercalated with the Deccan Traps of peninsular India. The tarsal bones, represented mainly by calcanea and astragali, occur in association with dental elements of palaeoryctid mammals: Deccanolestes hislopi Prasad and Sahni and D. robustus Prasad, Jaeger, Sahni, Gheerbrant, and Khajuria. Two size variants in the tarsals correlate well with the teeth of D. hislopi and D. robustus. Morphologically, the tarsal complex of Deccanolestes is quite different from that of other Cretaceous eutherians for which the relevant anatomy is known (Protungulatum and Procerberus). Rather, the tarsals of Deccanolestes exhibit a close affinity to the tarsal morphology of Archonta. A large number of tarsal characters indicate a highly arboreal mode of life for these animals. Presence of such specialized animals as early as the Cretaceous suggests that mammals had already diversified their locomotor adaptations by this time.
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Griffith, Oliver W., Arun R. Chavan, Stella Protopapas, Jamie Maziarz, Roberto Romero, and Gunter P. Wagner. "Embryo implantation evolved from an ancestral inflammatory attachment reaction." Proceedings of the National Academy of Sciences 114, no. 32 (July 26, 2017): E6566—E6575. http://dx.doi.org/10.1073/pnas.1701129114.
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The molecular changes that support implantation in eutherian mammals are necessary to establish pregnancy. In marsupials, pregnancy is relatively short, and although a placenta does form, it is present for only a few days before parturition. However, morphological changes in the uterus of marsupials at term mimic those that occur during implantation in humans and mice. We investigated the molecular similarity between term pregnancy in the marsupials and implantation in eutherian mammals using the gray short-tailed opossum (Monodelphis domestica) as a model. Transcriptomic analysis shows that term pregnancy in the opossum is characterized by an inflammatory response consistent with implantation in humans and mice. This immune response is temporally correlated with the loss of the eggshell, and we used immunohistochemistry to report that this reaction occurs at the materno–fetal interface. We demonstrate that key markers of implantation, including Heparin binding EGF-like growth factor and Mucin 1, exhibit expression and localization profiles consistent with the pattern observed during implantation in eutherian mammals. Finally, we show that there are transcriptome-wide similarities between the opossum attachment reaction and implantation in rabbits and humans. Our data suggest that the implantation reaction that occurs in eutherians is derived from an attachment reaction in the ancestral therian mammal which, in the opossum, leads directly to parturition. Finally, we argue that the ability to shift from an inflammatory attachment reaction to a noninflammatory period of pregnancy was a key innovation in eutherian mammals that allowed an extended period of intimate placentation.
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Menzies, B. R., G. Shaw, T. P. Fletcher, A. J. Pask, and M. B. Renfree. "208. Absence of GH-R exon 3 in marsupials and monotremes argues for a eutherian specific origin and fetal specific purpose of this domain." Reproduction, Fertility and Development 20, no. 9 (2008): 8. http://dx.doi.org/10.1071/srb08abs208.
Full textAbstract:
Growth hormone receptor (GH-R) plays a critical role in the control of growth and metabolism in all vertebrates. GH-R consists of 9 coding exons (2–10) in all eutherian mammals, while the chicken only has 8 coding exons, and does not have an orthologous region to eutherian exon 3. To further understand the evolutionary origins of exon 3 of the GH-R we have cloned the full-length GH-R sequence in a marsupial, the tammar wallaby to determine whether exon 3 was present or absent in marsupial liver cDNA. There was no evidence for the presence of an exon 3 containing mRNA in sequence of tammar pouch young and adult livers. We next examined the genomes of the platypus (a monotreme mammal) and the grey short-tailed opossum (another marsupial). Like the tammar, the GH-R gene of neither species contained an exon 3. GH receptor can obviously function in the absence of this exon, raising speculation about the function of this domain, if any, in eutherians. A comparison of exon 3 protein sequences within 16 species of eutherian mammals showed that there was ~75% homology in the domain despite only 3 residues being identical (Leu12, Gln13 and Pro17). Interestingly, we detected greater evolutionary divergence in exon 3 sequences from species that have variants of GH or prolactin (PRL) in their placentas. These data show that exon 3 was inserted into the GH-R after the divergence of marsupial and eutherian lineages at least 130 million years ago.
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Sherwin, WB, and ND Murray. "Population and Conservation Genetics of Marsupials." Australian Journal of Zoology 37, no. 3 (1989): 161. http://dx.doi.org/10.1071/zo9890161.
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This article summarises current knowledge of marsupial population genetics, and discusses its relevance to the conservation of marsupial species. It has been suggested that there is much lower genetic variation within marsupial populations than in eutherian mammals. This trend is not evident in the electrophoretic data summarised here. However, genetic differentiation between populations, subspecies, and species of marsupials appears to be slightly lower than comparable values for eutherians. Genetic estimates of migration between populations are scarce at present, but show values that are comparable with eutherians. Some studies of marsupial population genetics have used non-electrophoretic characteristics, or have addressed the possibility of selection on the characters analysed. Although few, these studies indicate the suitability of marsupials for such investigations. Recent debate over the theories and applications of conservation genetics has made it clear that more research is required on individual species. Given the record of extinction of marsupials in the last 200 years, it is important to test the applicability of these theories to individual marsupial species. Several examples are discussed emphasising the need for ecological studies that estimate the effective number of reproducing individuals per generation. This figure, called the effective size, is the corner- stone of conservation genetics theory, being an important determinant of both the rate of loss of variation between individuals, and the rate of inbreeding. The effective size of the mainland population of the eastern barred bandicoot, Perameles gunnii, appears to be only about one-tenth of its census number. This result is comparable with estimates made in other vertebrates, and demonstrates that many marsupial species which appear to have an adequate census size on ecological grounds may face genetic problems resulting from small effective size.
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Kawasaki, Kazuhiko, Jan C. C. Hu, and James P. Simmer. "Evolution of Klk4 and enamel maturation in eutherians." Biological Chemistry 395, no. 9 (September 1, 2014): 1003–13. http://dx.doi.org/10.1515/hsz-2014-0122.
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Abstract Kallikrein-related peptidase 4 (KLK4) is a secreted serine protease that degrades residual enamel proteins to facilitate their removal by ameloblasts, which increases mineralization and hardens the enamel. Mutations in human KLK4 cause hypomaturation amelogenesis imperfecta. Enamel formed by Klk4 null mice is normal in thickness and prism structure, but the enamel layer retains proteins, is hypomineralized, and undergoes rapid attrition following tooth eruption. We searched multiple databases, retrieved Klk4 and Klk5 from various mammalian genomes, and identified Klk4 in 46 boreoeutherian genomes. In non-Boreoeutheria, Klk4 was detected in only one afrotherian genome (as a pseudogene), and not in the other six afrotherian, two xenarthran, or three marsupial genomes. In contrast, Klk5 was detected in both marsupial and eutherian mammals. Our phylogenetic and mutation rate analyses support the hypothesis that Klk4 arose from Klk5 by gene duplication near the divergence of Afrotheria, Xenarthra and Boreoeutheria, and that functionally-differentiated Klk4 survived only in Boreoeutheria. Afrotherian mammals share the feature of delayed dental eruption relative to boreoeutherian mammals. KLK4 shortens the time required for enamel maturation and could have alleviated negative selection following mutations that resulted in thicker enamel or earlier tooth eruption, without reducing enamel hardness or causing dental attrition.
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Hwang, Jae Yeon, Jamie Maziarz, Günter P. Wagner, and Jean-Ju Chung. "Molecular Evolution of CatSper in Mammals and Function of Sperm Hyperactivation in Gray Short-Tailed Opossum." Cells 10, no. 5 (April 29, 2021): 1047. http://dx.doi.org/10.3390/cells10051047.
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Males have evolved species-specifical sperm morphology and swimming patterns to adapt to different fertilization environments. In eutherians, only a small fraction of the sperm overcome the diverse obstacles in the female reproductive tract and successfully migrate to the fertilizing site. Sperm arriving at the fertilizing site show hyperactivated motility, a unique motility pattern displaying asymmetric beating of sperm flagella with increased amplitude. This motility change is triggered by Ca2+ influx through the sperm-specific ion channel, CatSper. However, the current understanding of the CatSper function and its molecular regulation is limited in eutherians. Here, we report molecular evolution and conservation of the CatSper channel in the genome throughout eutherians and marsupials. Sequence analyses reveal that CatSper proteins are slowly evolved in marsupials. Using an American marsupial, gray short-tailed opossum (Monodelphis domestica), we demonstrate the expression of CatSper in testes and its function in hyperactivation and unpairing of sperm. We demonstrate that a conserved IQ-like motif in CatSperζ is required for CatSperζ interaction with the pH-tuned Ca2+ sensor, EFCAB9, for regulating CatSper activity. Recombinant opossum EFCAB9 can interact with mouse CatSperζ despite high sequence divergence of CatSperζ among CatSper subunits in therians. Our finding suggests that molecular characteristics and functions of CatSper are evolutionarily conserved in gray short-tailed opossum, unraveling the significance of sperm hyperactivation and fertilization in marsupials for the first time.
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Paolino, Annalisa, Laura R. Fenlon, Peter Kozulin, Elizabeth Haines, Jonathan W. C. Lim, Linda J. Richards, and Rodrigo Suárez. "Differential timing of a conserved transcriptional network underlies divergent cortical projection routes across mammalian brain evolution." Proceedings of the National Academy of Sciences 117, no. 19 (April 20, 2020): 10554–64. http://dx.doi.org/10.1073/pnas.1922422117.
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A unique combination of transcription factor expression and projection neuron identity demarcates each layer of the cerebral cortex. During mouse and human cortical development, the transcription factor CTIP2 specifies neurons that project subcerebrally, while SATB2 specifies neuronal projections via the corpus callosum, a large axon tract connecting the two neocortical hemispheres that emerged exclusively in eutherian mammals. Marsupials comprise the sister taxon of eutherians but do not have a corpus callosum; their intercortical commissural neurons instead project via the anterior commissure, similar to egg-laying monotreme mammals. It remains unknown whether divergent transcriptional networks underlie these cortical wiring differences. Here, we combine birth-dating analysis, retrograde tracing, gene overexpression and knockdown, and axonal quantification to compare the functions of CTIP2 and SATB2 in neocortical development, between the eutherian mouse and the marsupial fat-tailed dunnart. We demonstrate a striking degree of structural and functional homology, whereby CTIP2 or SATB2 of either species is sufficient to promote a subcerebral or commissural fate, respectively. Remarkably, we reveal a substantial delay in the onset of developmental SATB2 expression in mice as compared to the equivalent stage in dunnarts, with premature SATB2 overexpression in mice to match that of dunnarts resulting in a marsupial-like projection fate via the anterior commissure. Our results suggest that small alterations in the timing of regulatory gene expression may underlie interspecies differences in neuronal projection fate specification.
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Behringer, Richard R., Guy S. Eakin, and Marilyn B. Renfree. "Mammalian diversity: gametes, embryos and reproduction." Reproduction, Fertility and Development 18, no. 2 (2006): 99. http://dx.doi.org/10.1071/rd05137.
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The class Mammalia is composed of approximately 4800 extant species. These mammalian species are divided into three subclasses that include the monotremes, marsupials and eutherians. Monotremes are remarkable because these mammals are born from eggs laid outside of the mother’s body. Marsupial mammals have relatively short gestation periods and give birth to highly altricial young that continue a significant amount of ‘fetal’ development after birth, supported by a highly sophisticated lactation. Less than 10% of mammalian species are monotremes or marsupials, so the great majority of mammals are grouped into the subclass Eutheria, including mouse and human. Mammals exhibit great variety in morphology, physiology and reproduction. In the present article, we highlight some of this remarkable diversity relative to the mouse, one of the most widely used mammalian model organisms, and human. This diversity creates challenges and opportunities for gamete and embryo collection, culture and transfer technologies.
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Pharo, Elizabeth A. "Marsupial milk: a fluid source of nutrition and immune factors for the developing pouch young." Reproduction, Fertility and Development 31, no. 7 (2019): 1252. http://dx.doi.org/10.1071/rd18197.
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Marsupials have a very different reproductive strategy to eutherians. An Australian marsupial, the tammar wallaby (Macropus eugenii) has a very short pregnancy of about 26.5 days, with a comparatively long lactation of 300–350 days. The tammar mother gives birth to an altricial, approximately 400 mg young that spends the first 200 days postpartum (p.p.) in its mother’s pouch, permanently (0–100 days p.p.; Phase 2A) and then intermittently (100–200 days p.p.; Phase 2B) attached to the teat. The beginning of Phase 3 marks the first exit from the pouch (akin to the birth of a precocious eutherian neonate) and the supplementation of milk with herbage. The marsupial mother progressively alters milk composition (proteins, fats and carbohydrates) and individual milk constituents throughout the lactation cycle to provide nutrients and immunological factors that are appropriate for the considerable physiological development and growth of her pouch young. This review explores the changes in tammar milk components that occur during the lactation cycle in conjunction with the development of the young.
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Scanlon, Seth Thomas. "In non-eutherians, a third type of T cell." Science 371, no. 6536 (March 25, 2021): 1328.20–1330. http://dx.doi.org/10.1126/science.371.6536.1328-t.
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