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1
Hanks, M. C., C. A. Loomis, E. Harris, C. X. Tong, L. Anson-Cartwright, A. Auerbach, and A. Joyner. "Drosophila engrailed can substitute for mouse Engrailed1 function in mid-hindbrain, but not limb development." Development 125, no. 22 (November 15, 1998): 4521–30. http://dx.doi.org/10.1242/dev.125.22.4521.
Full textAbstract:
The Engrailed-1 gene, En1, a murine homologue of the Drosophila homeobox gene engrailed (en), is required for midbrain and cerebellum development and dorsal/ventral patterning of the limbs. In Drosophila, en is involved in regulating a number of key patterning processes including segmentation of the epidermis. An important question is whether, during evolution, the biochemical properties of En proteins have been conserved, revealing a common underlying molecular mechanism to their diverse developmental activities. To address this question, we have replaced the coding sequences of En1 with Drosophila en. Mice expressing Drosophila en in place of En1 have a near complete rescue of the lethal En1 mutant brain defect and most skeletal abnormalities. In contrast, expression of Drosophila en in the embryonic limbs of En1 mutants does not lead to repression of Wnt7a in the embryonic ventral ectoderm or full rescue of the embryonic dorsal/ventral patterning defects. Furthermore, neither En2 nor en rescue the postnatal limb abnormalities that develop in rare En1 null mutants that survive. These studies demonstrate that the biochemical activity utilized in mouse to mediate brain development has been retained by Engrailed proteins across the phyla, and indicate that during evolution vertebrate En proteins have acquired two unique functions during embryonic and postnatal limb development and that only En1 can function postnatally.
2
van den Heuvel, Marcel, John Klingensmith, Norbert Perrimon, and Roel Nusse. "Cell patterning in the Drosophila segment: engrailed and wingless antigen distributions in segment polarity mutant embryos." Development 119, Supplement (December 1, 1993): 105–14. http://dx.doi.org/10.1242/dev.119.supplement.105.
Full textAbstract:
By a complex and little understood mechanism, segment polarity genes control patterning in each segment of the Drosophila embryo. During this process, cell to cell communication plays a pivotal role and is under direct control of the products of segment polarity genes. Many of the cloned segment polarity genes have been found to be highly conserved in evolution, providing a model system for cellular interactions in other organisms. In Drosophila, two of these genes, engrailed and wingless, are expressed on either side of the parasegment border, wingless encodes a secreted molecule and engrailed a nuclear protein with a homeobox. Maintenance of engrailed expression is dependent on wingless and vice versa. To investigate the role of other segment polarity genes in the mutual control between these two genes, we have examined wingless and engrailed protein distribution in embryos mutant for each of the segment polarity genes. In embryos mutant for armadillo, dishevelled and porcupine, the changes in engrailed expression are identical to those in wingless mutant embryos, suggesting that their gene products act in the wingless pathway. In embryos mutant for hedgehog, fused, cubitus interruptus Dominant and gooseberry, expression of engrailed is affected to varying degrees. However wingless expression in the latter group decays in a similar way earlier than engrailed expression, indicating that these gene products might function in the maintenance of wingless expression. Using double mutant embryos, epistatic relationships between some segment polarity genes have been established. We present a model showing a current view of segment polarity gene interactions.
3
Hemmati-Brivanlou, A., J. R. de la Torre, C. Holt, and R. M. Harland. "Cephalic expression and molecular characterization of Xenopus En-2." Development 111, no. 3 (March 1, 1991): 715–24. http://dx.doi.org/10.1242/dev.111.3.715.
Full textAbstract:
We have isolated and characterized cDNAs corresponding to the Xenopus En-2 gene. Comparison of amino acid sequences between the entire Xenopus En-2 and the Drosophila engrailed proteins confirms conservation of sequences inside as well as proximal to the homeobox and reveals a region of similarity towards the N terminus. Two transcripts encode the Xenopus En-2 protein. Both transcripts are regulated temporally in an identical fashion and are likely to be transcribed from two copies of the En-2 gene. We have also analyzed the distribution of the protein in the head tissue and in the dissected brain of tailbud stage embryos. In addition to the main band of expression at the midbrain-hindbrain boundary, we show that the protein is expressed in three novel areas: the mandibular arch, the optic tectum and the region of anterior pituitary.
4
Peel, Andrew D., Maximilian J. Telford, and Michael Akam. "The evolution of hexapod engrailed-family genes: evidence for conservation and concerted evolution." Proceedings of the Royal Society B: Biological Sciences 273, no. 1595 (April 5, 2006): 1733–42. http://dx.doi.org/10.1098/rspb.2006.3497.
Full textAbstract:
Phylogenetic analyses imply that multiple engrailed-family gene duplications occurred during hexapod evolution, a view supported by previous reports of only a single engrailed-family gene in members of the grasshopper genus Schistocerca and in the beetle Tribolium castaneum . Here, we report the cloning of a second engrailed-family gene from Schistocerca gregaria and present evidence for two engrailed-family genes from four additional hexapod species. We also report the existence of a second engrailed-family gene in the Tribolium genome. We suggest that the engrailed and invected genes of Drosophila melanogaster have existed as a conserved gene cassette throughout holometabolous insect evolution. In total 11 phylogenetically diverse hexapod orders are now known to contain species that possess two engrailed-family paralogues, with in each case only one paralogue encoding the RS-motif, a characteristic feature of holometabolous insect invected proteins. We propose that the homeoboxes of hexapod engrailed-family paralogues are evolving in a concerted fashion, resulting in gene trees that overestimate the frequency of gene duplication. We present new phylogenetic analyses using non-homeodomain amino acid sequence that support this view. The S. gregaria engrailed-family paralogues provide strong evidence that concerted evolution might in part be explained by recurrent gene conversion. Finally, we hypothesize that the RS-motif is part of a serine-rich domain targeted for phosphorylation.
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Matsuzaki, M., and K. Saigo. "hedgehog signaling independent of engrailed and wingless required for post-S1 neuroblast formation in Drosophila CNS." Development 122, no. 11 (November 1, 1996): 3567–75. http://dx.doi.org/10.1242/dev.122.11.3567.
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The hedgehog gene product, secreted from engrailed-expressing neuroectoderm, is required for the formation of post-S1 neuroblasts in rows 2, 5 and 6. The hedgehog protein functions not only as a paracrine but also as an autocrine factor and its transient action on the neuroectoderm 1–2 hours (at 18 degrees C) prior to neuroblast delamination is necessary and sufficient to form normal neuroblasts. In contrast to epidermal development, hedgehog expression required for neuroblast formation is regulated by neither engrailed nor wingless. hedgehog and wingless bestow composite positional cues on the neuroectodermal regions for S2-S4 neuroblasts at virtually the same time and, consequently, post-S1 neuroblasts in different rows can acquire different positional values along the anterior-posterior axis. The average number of proneural cells for each of three eagle-positive S4-S5 neuroblasts was found to be 5–9, the same for S1 NBs. As with wingless (Chu-LaGraff et al., Neuron 15, 1041–1051, 1995), huckebein expression in putative proneural regions for certain post-S1 neuroblasts is under the control of hedgehog. hedgehog and wingless are involved in separate, parallel pathways and loss of either is compensated for by the other in NB 7–3 formation. NBs 6–4 and 7–3, arising from the engrailed domain, were also found to be specified by the differential expression of two homeobox genes, gooseberry-distal and engrailed.
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Desjobert, Cecile, Peter Noy, Tracey Swingler, Hannah Williams, Kevin Gaston, and Padma-Sheela Jayaraman. "The PRH/Hex repressor protein causes nuclear retention of Groucho/TLE co-repressors." Biochemical Journal 417, no. 1 (December 12, 2008): 121–32. http://dx.doi.org/10.1042/bj20080872.
Full textAbstract:
The PRH (proline-rich homeodomain) [also known as Hex (haematopoietically expressed homeobox)] protein is a transcription factor that functions as an important regulator of vertebrate development and many other processes in the adult including haematopoiesis. The Groucho/TLE (transducin-like enhancer) family of co-repressor proteins also regulate development and modulate the activity of many DNA-binding transcription factors during a range of diverse cellular processes including haematopoiesis. We have shown previously that PRH is a repressor of transcription in haematopoietic cells and that an Eh-1 (Engrailed homology) motif present within the N-terminal transcription repression domain of PRH mediates binding to Groucho/TLE proteins and enables co-repression. In the present study we demonstrate that PRH regulates the nuclear retention of TLE proteins during cellular fractionation. We show that transcriptional repression and the nuclear retention of TLE proteins requires PRH to bind to both TLE and DNA. In addition, we characterize a trans-dominant-negative PRH protein that inhibits wild-type PRH activity by sequestering TLE proteins to specific subnuclear domains. These results demonstrate that transcriptional repression by PRH is dependent on TLE availability and suggest that subnuclear localization of TLE plays an important role in transcriptional repression by PRH.
7
Royet, J., and R. Finkelstein. "Pattern formation in Drosophila head development: the role of the orthodenticle homeobox gene." Development 121, no. 11 (November 1, 1995): 3561–72. http://dx.doi.org/10.1242/dev.121.11.3561.
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Significant progress has been made towards understanding how pattern formation occurs in the imaginal discs that give rise to the limbs of Drosophila melanogaster. Here, we examine the process of regional specification that occurs in the eye-antennal discs, which form the head of the adult fruitfly. We demonstrate genetically that there is a graded requirement for the activity of the orthodenticle homeobox gene in forming specific structures of the developing head. Consistent with this result, we show that OTD protein is expressed in a graded fashion across the disc primordia of these structures and that different threshold levels of OTD are required for the formation of specific subdomains of the head. Finally, we provide evidence suggesting that otd acts through the segment polarity gene engrailed to specify medial head development.
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Villanueva, Sandra, Carlos Cespedes, Alexis Gonzalez, and Carlos P. Vio. "bFGF induces an earlier expression of nephrogenic proteins after ischemic acute renal failure." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 291, no. 6 (December 2006): R1677—R1687. http://dx.doi.org/10.1152/ajpregu.00023.2006.
Full textAbstract:
Recovery from acute renal failure (ARF) requires the replacement of injured cells with new cells that restore tubule epithelial integrity. We described recently the expression of a wide range of nephrogenic proteins in tubular cells after ARF induced by ischemia-reperfusion (I/R) (Villanueva S, Cespedes C, and Vio CP. Am J Physiol Regul Integr Comp Physiol 290: R861–R870, 2006). These markers, namely, Vimentin, neural cell adhesion molecules (Ncam), basic fibroblast growth factor (bFGF), paired homeobox-2 (Pax-2), bone morphogene protein-7 (BMP-7), Noggin, Lim-1, Engrailed, Smad, phospho-Smad, hypoxia-induced factor-1α (HIF-1α), VEGF, and Tie-2, are expressed in a time frame similar to that observed in normal kidney development. bFGF participates in early kidney development as a morphogen involved in mesenchyme/epithelial transition, and it is reexpressed in the recovery phase of ARF. To test the hypothesis that bFGF can accelerate the regeneration after renal damage, we used recombinant bFGF and studied the expression pattern of the above described morphogens in ARF. Male Sprague-Dawley rats were subjected to 30 min of renal ischemic injury and were injected with bFGF 30 μg/kg followed by reperfusion. Rats were killed and the expression of nephrogenic proteins were analyzed by immunohistochemistry and Western blot analysis. In the animals subjected to I/R treated with bFGF, we observed a 12- to 24-h earlier and more abundant reexpression of the proteins Ncam, bFGF, Pax-2, BMP-7, Noggin, Lim-1, Engrailed, VEGF, and Tie-2 than the I/R untreated rats. In addition, we observed a reduction in renal damage markers ED-1 and α-smooth muscle actin. These results indicate that bFGF can participate in the regeneration process and suggest that the treatment with bFGF can induce an earlier regeneration process after ischemic acute renal failure.
9
Montross, W. T., H. Ji, and P. D. McCrea. "A beta-catenin/engrailed chimera selectively suppresses Wnt signaling." Journal of Cell Science 113, no. 10 (May 15, 2000): 1759–70. http://dx.doi.org/10.1242/jcs.113.10.1759.
Full textAbstract:
beta-catenin plays an integral role in cell-cell adhesion by linking the cadherin complex of the adherens junction to the underlying actin cytoskeleton. In addition, beta-catenin transduces intracellular signals within the Wnt developmental pathway that are crucial to the proper establishment of embryonic axes and pattern formation of early mesoderm and ectoderm. For example, in the context of a defined dorsal ‘organizer’ region of early Xenopus embryos, beta-catenin enters the nucleus and associates with transcription factors of the HMG (High Mobility Group) Lef/Tcf protein family. Consequently, genes such as siamois, a homeobox gene contributing to the specification of the dorsoanterior axis, are activated. To further examine the role that beta-catenin plays in Wnt signaling, we generated a chimeric protein, beta-Engrailed (beta-Eng), in which the C-terminal trans-activation domain of beta-catenin is replaced with the transcriptional repression domain of Drosophila Engrailed. Dorsal overexpression of this mRNA in early Xenopus embryos leads to suppression of organizer-specific molecular markers such as siamois, Xnr-3 and goosecoid, corresponding with the dramatic morphological ventralization of embryos. Ventralized embryos further exhibit reduced activity of the Wnt pathway, as indicated by the loss of the notochord/organizer marker, chordin. Importantly, beta-Eng associates and functions normally with the known components of the cadherin complex, providing the experimental opportunity to repress beta-catenin's signaling function apart from its role in cadherin-mediated cell-cell adhesion.
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Dibner, Charna, Sarah Elias, and Dale Frank. "XMeis3 protein activity is required for proper hindbrain patterning in Xenopus laevis embryos." Development 128, no. 18 (September 15, 2001): 3415–26. http://dx.doi.org/10.1242/dev.128.18.3415.
Full textAbstract:
Meis-family homeobox proteins have been shown to regulate cell fate specification in vertebrate and invertebrate embryos. Ectopic expression of RNA encoding the Xenopus Meis3 (XMeis3) protein caused anterior neural truncations with a concomitant expansion of hindbrain and spinal cord markers in Xenopus embryos. In naïve animal cap explants, XMeis3 activated expression of posterior neural markers in the absence of pan-neural markers. Supporting its role as a neural caudalizer, XMeis3 is expressed in the hindbrain and spinal cord. We show that XMeis3 acts like a transcriptional activator, and its caudalizing effects can be mimicked by injecting RNA encoding a VP16-XMeis3 fusion protein. To address the role of endogenous XMeis3 protein in neural patterning, XMeis3 activity was antagonized by injecting RNA encoding an Engrailed-XMeis3 antimorph fusion protein or XMeis3 antisense morpholino oligonucleotides. In these embryos, anterior neural structures were expanded and posterior neural tissues from the midbrain-hindbrain junction through the hindbrain were perturbed. In neuralized animal cap explants, XMeis3-antimorph protein modified caudalization by basic fibroblast growth factor and Wnt3a. XMeis3-antimorph protein did not inhibit caudalization per se, but re-directed posterior neural marker expression to more anterior levels; it reduced expression of spinal cord and hindbrain markers, yet increased expression of the more rostral En2 marker. These results provide evidence that XMeis3 protein in the hindbrain is required to modify anterior neural-inducing activity, thus, enabling the transformation of these cells to posterior fates.
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Chu-Lagraff, Quynh, Dorthy M. Wright, Leslie Klis McNeil, and Chris Q. Doe. "The prospero gene encodes a divergent homeodomain protein that controls neuronal identity in Drosophila." Development 113, Supplement_2 (April 1, 1991): 79–85. http://dx.doi.org/10.1242/dev.113.supplement_2.79.
Full textAbstract:
The Drosophila central nervous system (CNS) develops from a population of stem cells called neuroblasts; each neuroblast goes through an invariant cell lineage to produce a characteristic family of neurons or glia. We are interested in the molecular mechanisms controlling neuroblast cell lineage. Recently we identified the prospero (pros) gene, which is expressed in embryonic neuroblasts. Loss of pros function results in aberrant expression of the homeobox genes fushi tarazu, evenskipped and engrailed in a subset of neuroblast progeny, suggesting that pros plays an early and fundamental role in the specification of neuronal fate (Doe et al. 1991). Here we show that the pros gene encodes a highly divergent homeodomain. The homeodomain contains several of the most conserved amino acids characteristic of known homeodomains, yet it is considerably less basic than previously identified homeodomains. These data are consistent with a model in which pros controls neuroblast cell lineages by regulating gene expression.
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Mlodzik, M., G. Gibson, and W. J. Gehring. "Effects of ectopic expression of caudal during Drosophila development." Development 109, no. 2 (June 1, 1990): 271–77. http://dx.doi.org/10.1242/dev.109.2.271.
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The effects of heat-shock-induced ectopic expression of the homeobox gene caudal (cad) at all stages of Drosophila development have been examined. Presence of cad protein (CAD) at the anterior end of cellular blastoderm embryos was found to disrupt head development and segmentation, due to alteration of the expression of segmentation genes such as fushi tarazu and engrailed, as well as repression of head-determining genes such as Deformed. These results support the conclusion that, while CAD is probably required to activate transcription of fushi tarazu in the posterior half of the embryo, it should not be expressed in the anterior half prior to gastrulation, and thus suggest a role for the CAD gradient. Ectopic expression of CAD at later stages of development has no obvious effects on embryogenesis or imaginal disc development, suggesting that the homeotic genes of the Antennapedia and Bithorax Complexes are almost completely epistatic to caudal.
13
Goriely, A., M. Stella, C. Coffinier, D. Kessler, C. Mailhos, S. Dessain, and C. Desplan. "A functional homologue of goosecoid in Drosophila." Development 122, no. 5 (May 1, 1996): 1641–50. http://dx.doi.org/10.1242/dev.122.5.1641.
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We have cloned a Drosophila homologue (D-gsc) of the vertebrate homeobox gene goosecoid (gsc). In the Gsc proteins, the pressure for conservation has been imposed on the homeodomain, the functional domain of the protein: sequence homology is limited to the homeodomain (78% identity) and to a short stretch of 7 aminoacids also found in other homeoproteins such as Engrailed. Despite this weak homology, D-gsc is able to mimic gsc function in a Xenopus assay, as shown by its ability to rescue the axis development of a UV-irradiated embryo. Moreover, our data suggest that the position of insect and vertebrate gsc homologues within a regulatory network has also been conserved: D-gsc expression is controlled by decapentaplegic, orthodenticle, sloppy-paired and tailless whose homologues control gsc expression (for BMP4 and Otx-2), or are expressed at the right time and the right place (for XFKH1/Pintallavis and Tlx) to be interacting with gsc during vertebrate development. However, the pattern of D-gsc expression in ectodermal cells of the nervous system and foregut cannot easily be reconciled with that of vertebrate gsc mesodermal expression, suggesting that its precise developmental function might have diverged. Still, this comparison of domains of expression and functions among Gsc proteins could shed light on a common origin of gut formation and/or on basic cellular processes. The identification of gsc target genes and/or other genes involved in similar developmental processes will allow the definition of the precise phylogenetic relationship among Gsc proteins.
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Tear, G., M. Akam, and A. Martinez-Arias. "Isolation of an abdominal-A gene from the locust Schistocerca gregaria and its expression during early embryogenesis." Development 110, no. 3 (November 1, 1990): 915–25. http://dx.doi.org/10.1242/dev.110.3.915.
Full textAbstract:
Using sequence homology to Drosophila homeobox-containing genes, we have cloned a homologue of abdominal-A from the locust Schistocerca gregaria. The Schistocerca clone encodes a stretch of 78 amino acids including the homeodomain and its flanking regions identical to the corresponding region of abdominal-A. We have shown by in situ hybridization that this gene is transcribed and have used an antibody raised against its protein product to examine the expression of abdominal-A during early Schistocerca embryogenesis. Schistocerca is a short germ insect. Although the segmented body plan is very similar to that of Drosophila, the segments are generated sequentially by a process of growth, not simultaneously by subdivision of a syncytial blastoderm. In both organisms, abdominal-A is expressed throughout the abdomen from a sharp anterior boundary located within the first abdominal segment (A1). The initial activation of the genes in the two species differs. Schistocerca initiates expression in a small group of cells in the anterior of A2, shortly after this segment is defined by the appearance of engrailed protein. This contrasts with the appearance of abdominal-A expression in Drosophila, which appears simultaneously throughout the entire abdomen.
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Simmonds, A. J., and J. B. Bell. "A genetic and molecular analysis of an invectedDominant mutation in Drosophila melanogaster." Genome 41, no. 3 (June 1, 1998): 381–90. http://dx.doi.org/10.1139/g98-026.
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The invected gene of Drosophila melanogaster is a homeobox-containing gene that is closely related to engrailed. A dominant gain of function allele, invectedDominant, was derived from mutagenesis of a dominant allele of vestigial, In(2R)vgW. A careful analysis of the phenotype of invectedDominant shows that it is associated with a transformation of the anterior compartment of the wing to a posterior fate. This transformation is normally limited to the wing blade itself and does not involve the remaining tissues derived from the wing imaginal disc, including the wing hinge and dorsal thorax of the fly. The ectopic expression of invected protein associated with invectedDominant correlates spatially with the normal expression pattern of vestigial in the wing imaginal disc, suggesting that control elements of vestigial are driving ectopic invected expression. This was confirmed by sequence analysis that shows that the dominant vestigial activity was eliminated by a deletion that removes the 3' portion of the vestigial coding region. This leaves a gene fusion wherein the vestigial enhancer elements are still juxtaposed immediately 5' to the invected transcriptional start site, but with the vg sequences harboring an additional lesion. Unlike recessive invected alleles, the invectedDominant allele produces an observable phenotype, and as such, should prove useful in determining the role of invected in patterning the wing imaginal disc. Genetic analysis has shown that mutations of polyhomeotic, a gene involved in regulating engrailed expression, cause a reproducible alteration in the invectedDominant phenotype. Finally, the invectedDominant allele should prove valuable for identifying and characterizing genes that are activated within the posterior compartment. A screen using various lacZ lines that are asymmetrically expressed in an anterior-posterior manner in the wing imaginal disc isolated one line that shows posterior-specific expression within the transformed anterior compartment.Key words: Drosophila, development, dominant mutation, ectopic, wings.
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Logan, C., A. Hornbruch, I. Campbell, and A. Lumsden. "The role of Engrailed in establishing the dorsoventral axis of the chick limb." Development 124, no. 12 (June 15, 1997): 2317–24. http://dx.doi.org/10.1242/dev.124.12.2317.
Full textAbstract:
Expression and mutation analyses in mice suggest that the homeobox-containing gene Engrailed (En) plays a role in dorsoventral patterning of the limb. During the initial stages of limb bud outgrowth, En-1 mRNA and protein are uniformly distributed throughout the ventral limb bud ectoderm. Limbs of En-1(−/−) mice display a double dorsal phenotype suggesting that normal expression of En-1 in the ventral ectoderm is required to establish and/or maintain ventral limb characteristics. Loss of En-1 function also results in ventral expansion of the apical ectodermal ridge (AER), suggesting that En-1 is also required for proper formation of the AER. To further investigate the role En plays in dorsoventral patterning and AER formation, we have used the replication competent retroviral vector, RCAS, to mis-express mouse En-1 in the early chick limb bud. We show that ectopic En-1 expression in dorsal ectoderm is sufficient to repress the endogenous expression of the dorsal ectodermal marker Wnt7a, with a resultant decrease in Lmx1 expression in underlying dorsal mesenchyme. Furthermore, the AER is disrupted morphologically and the expression patterns of the AER signalling molecules Fgf-8 and Fgf-4 are altered. Consistent with recent evidence that there is a reciprocal interaction between signalling molecules in the dorsal ectoderm, AER, and zone of polarising activity (ZPA), loss of Wnt7a, Fgf-8 and Fgf-4 expression leads to a decrease in expression of the signalling molecule Shh in the ZPA. These results strongly support the idea that, in its normal domain of expression, En-1 represses Wnt7a-mediated dorsal differentiation by limiting the expression of Wnt7a to the dorsal ectoderm. Furthermore, our results provide additional evidence that En-1 is involved in AER formation and suggest that En-1 may act to define ventral ectodermal identity.
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Fan, M. J., and S. Y. Sokol. "A role for Siamois in Spemann organizer formation." Development 124, no. 13 (July 1, 1997): 2581–89. http://dx.doi.org/10.1242/dev.124.13.2581.
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The vertebrate body plan is specified in the early embryo through the inductive influence of the organizer, a special region that forms on the dorsalmost side of the embryo at the beginning of gastrulation. In Xenopus, the homeobox gene Siamois is activated prior to gastrulation in the area of organizer activity and is capable of inducing a secondary body axis when ectopically expressed. To elucidate the function of endogeneous Siamois in dorsoventral axis formation, we made a dominant repressor construct (SE) in which the Siamois homeodomain was fused to an active repression domain of Drosophila engrailed. Overexpression of 1–5 pg of this chimeric mRNA in the early embryo blocks axis development and inhibits activation of dorsal, but not ventrolateral, marginal zone markers. At similar expression levels, SE proteins with altered DNA-binding specificity do not have the same effect. Coexpression of mRNA encoding wild-type Siamois, but not a mutated Siamois, restores dorsal development to SE embryos. Furthermore, SE strongly blocks axis formation triggered by beta-catenin but not by the organizer product noggin. These results suggest that Siamois function is essential for beta-catenin-mediated formation of the Spemann organizer, and that Siamois acts prior to noggin in specifying dorsal development.
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Heimbucher, Thomas, Christina Murko, Baubak Bajoghli, Narges Aghaallaei, Anja Huber, Ronald Stebegg, Dirk Eberhard, Maria Fink, Antonio Simeone, and Thomas Czerny. "Gbx2 and Otx2 Interact with the WD40 Domain of Groucho/Tle Corepressors." Molecular and Cellular Biology 27, no. 1 (October 23, 2006): 340–51. http://dx.doi.org/10.1128/mcb.00811-06.
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ABSTRACT One of the earliest organizational decisions in the development of the vertebrate brain is the division of the neural plate into Otx2-positive anterior and Gbx2-positive posterior territories. At the junction of these two expression domains, a local signaling center is formed, known as the midbrain-hindbrain boundary (MHB). This tissue coordinates or “organizes” the development of neighboring brain structures, such as the midbrain and cerebellum. Correct positioning of the MHB is thought to depend on mutual repression involving these two homeobox genes. Using a cell culture colocalization assay and coimmunoprecipitation experiments, we show that engrailed homology region 1 (eh1)-like motifs of both transcription factors physically interact with the WD40 domain of Groucho/Tle corepressor proteins. In addition, heat shock-induced expression of wild-type and mutant Otx2 and Gbx2 in medaka embryos demonstrates that Groucho is required for the repression of Otx2 by Gbx2. On the other hand, the repressive functions of Otx2 on Gbx2 do not appear to be dependent on corepressor interaction. Interestingly, the association of Groucho with Otx2 is also required for the repression of Fgf8 in the MHB. Therefore Groucho/Tle family members appear to regulate key aspects in the MHB development of the vertebrate brain.
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Inbal, Adi, Naomi Halachmi, Charna Dibner, Dale Frank, and Adi Salzberg. "Genetic evidence for the transcriptional-activating function of Homothorax during adult fly development." Development 128, no. 18 (September 15, 2001): 3405–13. http://dx.doi.org/10.1242/dev.128.18.3405.
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Homothorax (HTH) is a homeobox-containing protein, which plays multiple roles in the development of the embryo and the adult fly. HTH binds to the homeotic cofactor Extradenticle (EXD) and translocates it to the nucleus. Its function within the nucleus is less clear. It was shown, mainly by in vitro studies, that HTH can bind DNA as a part of ternary HTH/EXD/HOX complexes, but little is known about the transcription regulating function of HTH-containing complexes in the context of the developing fly. Here we present genetic evidence, from in vivo studies, for the transcriptional-activating function of HTH. The HTH protein was forced to act as a transcriptional repressor by fusing it to the Engrailed (EN) repression domain, or as a transcriptional activator, by fusing it to the VP16 activation domain, without perturbing its ability to translocate EXD to the nucleus. Expression of the repressing form of HTH in otherwise wild-type imaginal discs phenocopied hth loss of function. Thus, the repressing form was working as an antimorph, suggesting that normally HTH is required to activate the transcription of downstream target genes. This conclusion was further supported by the observation that the activating form of HTH caused typical hth gain-of-function phenotypes and could rescue hth loss-of-function phenotypes. Similar results were obtained with XMeis3, the Xenopus homologue of HTH, extending the known functional similarity between the two proteins. Competition experiments demonstrated that the repressing forms of HTH or XMeis3 worked as true antimorphs competing with the transcriptional activity of the native form of HTH. We also describe the phenotypic consequences of HTH antimorph activity in derivatives of the wing, labial and genital discs. Some of the described phenotypes, for example, a proboscis-to-leg transformation, were not previously associated with alterations in HTH activity. Observing the ability of HTH antimorphs to interfere with different developmental pathways may direct us to new targets of HTH. The HTH antimorph described in this work presents a new means by which the transcriptional activity of the endogenous HTH protein can be blocked in an inducible fashion in any desired cells or tissues without interfering with nuclear localization of EXD.
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Ermakova, G. V., E. M. Alexandrova, O. V. Kazanskaya, O. L. Vasiliev, M. W. Smith, and A. G. Zaraisky. "The homeobox gene, Xanf-1, can control both neural differentiation and patterning in the presumptive anterior neurectoderm of the Xenopus laevis embryo." Development 126, no. 20 (October 15, 1999): 4513–23. http://dx.doi.org/10.1242/dev.126.20.4513.
Full textAbstract:
From the onset of neurectoderm differentiation, homeobox genes of the Anf class are expressed within a region corresponding to the presumptive telencephalic and rostral diencephalic primordia. Here we investigate functions of the Xenopus member of Anf, Xanf-1, in the differentiation of the anterior neurectoderm. We demonstrate that ectopic Xanf-1 can expand the neural plate at expense of adjacent non-neural ectoderm. In tadpoles, the expanded regions of the plate developed into abnormal brain outgrowths. At the same time, Xanf-1 can inhibit terminal differentiation of primary neurones. We also show that, during gastrula/neurula stages, the exogenous Xanf-1 can downregulate four transcription regulators, XBF-1, Otx-2, Pax-6 and the endogenous Xanf-1, that are expressed in the anterior neurectoderm. However, during further development, when the exogenous Xanf-1 was presumably degraded, re-activation of XBF-1, Otx-2 and Pax-6 was observed in the abnormal outgrowths developed from blastomeres microinjected with Xanf-1 mRNA. Other effects of the ectopic Xanf-1 include cyclopic phenotype and inhibition of the cement gland, both by Otx-2-dependent and -independent mechanisms. Using fusions of Xanf-1 with the repressor domain of Drosophila engrailed or activator domain of herpes virus VP16 protein, we showed that most of the observed effects of Xanf-1 were probably elicited by its functioning as a transcription repressor. Altogether, our data indicate that the repressor function of Xanf-1 may be necessary for regulation of both neural differentiation and patterning in the presumptive anterior neurectoderm.
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Sater, A. K., J. M. Alderton, and R. A. Steinhardt. "An increase in intracellular pH during neural induction in Xenopus." Development 120, no. 2 (February 1, 1994): 433–42. http://dx.doi.org/10.1242/dev.120.2.433.
Full textAbstract:
In this paper, we show that an intracellular alkalinization of the dorsal ectoderm cells is among the earliest responses to neural induction in Xenopus. Planar explants of the dorsal marginal zone were prepared from embryos that had been microinjected during cleavage stages with the fluorescent pH indicator bis-carboxyethyl-carboxyfluorescein-dextran (BCECF-dextran), and intracellular pH (pHi) was monitored continuously by emission ratio microfluorimetry. During stage 10.5, the dorsal ectoderm cells undergo a sustained intracellular alkalinization of approximately 0.1 pH units in response to neural induction; in the absence of the inductive signal, the pH of the dorsal ectoderm cells decreases slightly. Ectoderm cells within planar explants of the ventral marginal zone show little change in pH during a similar period. This increase in intracellular pH is inhibited by 4, 4′-dihydrodiisothiocyanatostilbene-2, 2′-disulfonate (H2DIDS) or a low Na+/high Cl- medium, treatments that presumably affect anion transport. Under these conditions, expression of the anterior neural-specific homeobox gene engrailed is not detected, while the notochord-specific epitope recognized by the Tor-70 antibody is expressed in the presence of H2DIDS. This characteristic alkalinization is not evoked by pharmacological agents that reportedly alter ectodermal developmental pathways in Xenopus embryos, such as NH4Cl, phorbol esters, or cAMP-dependent protein kinase agonists. Our results suggest that an ionic regulatory event may participate in the regulation of gene expression in response to neural induction.
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Yu, X., T. R. St Amand, S. Wang, G. Li, Y. Zhang, Y. P. Hu, L. Nguyen, M. S. Qiu, and Y. P. Chen. "Differential expression and functional analysis of Pitx2 isoforms in regulation of heart looping in the chick." Development 128, no. 6 (March 15, 2001): 1005–13. http://dx.doi.org/10.1242/dev.128.6.1005.
Full textAbstract:
Pitx2, a bicoid-related homeobox gene, plays a crucial role in the left-right axis determination and dextral looping of the vertebrate developing heart. We have examined the differential expression and function of two Pitx2 isoforms (Pitx2a and Pitx2c) that differ in the region 5′ to the homeodomain, in early chick embryogenesis. Northern blot and RT-PCR analyses indicated the existence of Pitx2a and Pitx2c but not Pitx2b in the developing chick embryos. In situ hybridization demonstrated a restricted expression of Pitx2c in the left lateral plate mesoderm (LPM), left half of heart tube and head mesoderm, but its absence in the extra-embryonic tissues where vasculogenesis occurs. RT-PCR experiments revealed that Pitx2a is absent in the left LPM, but is present in the head and extra-embryonic mesoderm. However, ectopic expression of either Pitx2c or Pitx2a via retroviral infection to the right LMP equally randomized heart looping direction. Mapping of the transcriptional activation function to the C terminus that is identical in both isoforms explained the similar results obtained by the gain-of-function approach. In contrast, elimination of Pitx2c expression from the left LMP by antisense oligonucleotide resulted in a randomization of heart looping, while treatment of embryos with antisense oligonucleotide specific to Pitx2a failed to generate similar effect. We further constructed RCAS retroviral vectors expressing dominant negative Pitx2 isoforms in which the C-terminal transcriptional activation domain was replaced by the repressor domain of the Drosophila Engrailed protein (En(r)). Ectopic expression of Pitx2c-En(r), but not Pitx2a-En(r), to the left LPM randomized the heart looping. The results thus demonstrate that Pitx2c plays a crucial role in the left-right axis determination and rightward heart looping during chick embryogenesis.
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Wang, Gang G., Martina P. Pasillas, and Mark P. Kamps. "Fusion to Vp16 Converts MEIS1 into an Oncoprotein That Immortalizes Progenitors and Causes AML in the Absence of Coexpressed Hox Genes: Hoxa7 and Hoxa9 Induced Further Stem Cell Gene Transcription in Vp16MEIS1 Progenitors." Blood 106, no. 11 (November 16, 2005): 662. http://dx.doi.org/10.1182/blood.v106.11.662.662.
Full textAbstract:
Abstract MEIS1 and Hoxa9 are homeobox transcription factors that promote self-renewal in hematopoietic progenitors. MEIS1 does not induce leukemia, but cooperates strongly with Hoxa9 to produce acute myeloid leukemia (AML). Previously, we demonstrated that Hoxa9 blocks differentiation of myeloid progenitors that do not express MEIS1 and do not induce leukemic. Coexpression of MEIS1 causes transcription of genes that segregate with the leukemia-initiating subset of human AML blasts, such as CD34 and FLT3. We designate these genes as leukemic stem cell genes, or LSC genes. MEIS1 promoted LCS gene transcription by a mechanism that requires interaction with PBX and DNA, and that also requires a short MEIS1 C-terminal transactivation domain (CTD). Here we use a dominant transactivating or transrepressing form of MEIS1 to determine whether the activation or repression function of Pbx:MEIS1 complexes is sufficient to cause myeloid leukemia in combination with coexpressed Hoxa9. Surprisingly, fusion of MEIS1 to the Vp16 transactivation domain (but not the engrailed transrepression domain) produced an autonomous oncoprotein that immortalized progenitors and caused myeloid leukemias without the need for coexpressed exogenous or endogenous Hox genes. Like MEIS1, Vp16MEIS1 required binding to Pbx and DNA for immortalization; however, the CTD was not necessary in the context of Vp16MEIS1. This suggests that the CTD participates in target gene activation in AML blasts, a function replaced by Vp16 in its absence. Retroviral expression of Hoxa9 or Hoxa7 induced a further, strong, transcriptional upregulation of LSC genes in Vp16MEIS1 progenitors and elevated their leukemic potential to the level of bona fide AML blasts. These data suggest that transactivation is the essential function of Pbx:MEIS1 complexes in AML, and that HOX proteins cooperate with Pbx:MEIS1 complexes to activate transcription of early progenitor genes whose expression is required for human AML.
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Gu, Yi, Carmelita J. Alvares, Aparna C. Jasti, Michael Jansen, Judy Bean, Anil G. Jegga, Bruce J. Aronow, and David A. Williams. "Alteration of RhoH Expression Is Associated with Human Diffuse Large B-Cell Lymphoma." Blood 104, no. 11 (November 16, 2004): 4298. http://dx.doi.org/10.1182/blood.v104.11.4298.4298.
Full textAbstract:
Abstract An increasing number of Rho GTPase family proteins have been demonstrated to play critical roles in blood and immune cell development and function. The newly defined RhoH gene has been previously demonstrated to be mutated in lymphoma samples (Dallery et al, 1995; Pasqualucci et al, 2001). These alterations include chromosomal rearrangements and a high frequency of somatic mutations (up to 46%) in human non-Hodgkin’s lymphomas and diffuse large B-cell lymphoma. The RhoH gene encodes a novel hematopoietic-specific member of the RhoE subfamily, which is GTPase deficient, remaining in the active, GTP-bound state. Thus the activity of RhoH is likely regulated by the level of the protein expressed in the cell. The somatic mutations in the RhoH gene have been mapped to a 1.6kb hypermutable region in the intron 1, suggesting the possibility of dysregulated RhoH expression. However, levels of RhoH expression have not been directly measured in these hematopoietic tumors and so it remains unclear whether these mutations translate into aberrant RhoH expression. We utilized quantitative real-time RT-PCR to measure RhoH transcript levels in primary DLBCL patient samples. Based on morphologic and immunophenotypic analysis, 17 DLBCL positive samples and 14 normal control samples were used for our study. The levels of TATA-box binding protein (TBP) and human phosphogycerate kinase (HPGK) cDNAs were also examined simultaneously for relative expression normalization. RhoH transcript levels in a subset of the DLBCL samples were markedly reduced. In particular, 6 of 17 (~35%) tested samples showed a greater than 3-fold reduction in RhoH expression based on both RhoH/TBP and RhoH/HPGK ratios when compared with the median RhoH expression level of 14 normal samples. Overall, RhoH expression levels of the DLBCL group were significantly altered (mainly decreased) as compared with those of the normal group (p < 0.04, student T-test). To further determine correlation of the abnormal RhoH expression with somatic mutations in the hypermutable region of the RhoH gene in the DLBCL samples, we performed genomic PCR amplification and sequencing analysis of this region from the normal and DLBCL samples. In addition, we utilized a computational approach (Trafac - http://trafac.cchmc.org) to identify evolutionarily conserved putative transcription factor binding sites (TFBS) between human and other species in the hypermutable region. 13 conserved TFBS between human and mouse were identified in the hypermutable region. Mutations in the DLBCL patients are localized in 6 of these predicted TFBS, including pancreatic and duodenal homeobox 1 (PDX1), zinc-finger binding protein-89 (ZBP-89), lymphoid enhancer factor 1 (LEF-1), BRIGHT, engrailed 1 and myelin transcription factor 1 (MyT1). Interestingly, LEF-1 and BRIGHT are B cell-specific transcription activators. These results suggest that RhoH expression is frequently altered in 35–40% of DLBCL samples and mutations in the hypermutable region of the RhoH gene in several cases encompass core binding sequences of transcription factors important in B cell development.
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Cao, Manxiu, Lei Zhang, Jiaqi Chen, Cangyu Wang, Junhong Zhao, Xiang Liu, Yongjing Yan, Yue Tang, Zixiu Chen, and Haihong Li. "Differential antigen expression between human apocrine sweat glands and eccrine sweat glands." European Journal of Histochemistry 67, no. 1 (December 22, 2022). http://dx.doi.org/10.4081/ejh.2023.3559.
Full textAbstract:
Bromhidrosis has a great negative impact on personal occupation and social psychology. It is not yet clear whether bromhidrosis is caused by apocrine sweat glands or the co-action of apocrine sweat glands and eccrine sweat glands. To distinguish between apocrine sweat glands and eccrine sweat glands, specific antigen markers for apocrine sweat glands and eccrine sweat glands must be found first. In the study, we detected the expression of K7, K18, K19, Na+-K+-2Cl- cotransporter 1 (NKCC1), carbonic anhydrase II (CAII), Forkhead transcription factor a1 (Foxa1), homeobox transcription factor engrailed homeobox1 (En1), gross cystic disease fluid protein-15 (GCDFP-15), mucin-1 (MUC-1), cluster of differentiation 15 (CD15) and apolipoprotein (APOD) in eccrine sweat glands and apocrine sweat glands by immunofluorescence staining. The results showed that K7, K18, K19, Foxa1, GCDFP-15 and MUC-1 were expressed in both apocrine and eccrine sweat glands, CD15 and APOD were only expressed in apocrine sweat glands, and CAII, NKCC1 and En1 were only expressed in eccrine sweat glands. We conclude that CD15 and APOD can serve as specific markers for apocrine sweat glands, while CAII, NKCC1 and En1 can serve as specific markers for eccrine sweat glands to differentiate the two sweat glands.
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Hui, Zhixuan, Bo Wang, Zhengyan Liu, Jinhui Wei, Jiaxing Gan, Marene Landstrom, Yabing Mu, and Guangxiang Zang. "TGFβ‐induced EN1 promotes tumor budding of adenoid cystic carcinoma in patient‐derived organoid model." International Journal of Cancer, January 28, 2024. http://dx.doi.org/10.1002/ijc.34856.
Full textAbstract:
AbstractAdenoid cystic carcinoma (ACC) and basal cell adenoma (BCA) share many histological characteristics and often need a differential diagnosis in clinical pathology. Recently, we found homeobox protein engrailed‐1 (EN1) was a potential diagnostic marker for ACC in an organoids library of salivary gland tumors (SGTs). Here we aim to confirm EN1 as a differential diagnostic marker for ACC, and further investigate the regulatory mechanism and biological function of EN1 in tumor progression. The transcriptional analysis, quantitative polymerase chain reaction, Western blot and immunohistochemistry staining were performed and revealed that EN1 was specifically and highly expressed in ACC, and accurately differentiated ACC from BCA. Furthermore, TGFβ signaling pathway was found associated with ACC, and the regulation of EN1 through TGFβ was detected in the human ACC cell lines and patient‐derived organoids (PDOs). TGFβ‐induced EN1 was important in promoting tumor budding in the PDOs model. Interestingly, a high level of EN1 and TGFβ1 in the budding tips was observed in ACC clinical samples, and the expression of EN1 and TGFβ1 in ACC was significantly associated with the clinical stage. In summary, our study verified EN1 is a good diagnostic marker to differentiate ACC from BCA. TGFβ‐induced EN1 facilitates the tumor budding of ACC, which might be an important mechanism related to the malignant phenotype of ACC.