Letteratura scientifica selezionata sul tema "Myosin 1g"

ObjectiveOne of the challenges in hypertrophic cardiomyopathy (HCM) is to determine the pathogenicity of genetic variants and to establish genotype/phenotype correlations. This study aimed to: (1) demonstrate that MYBPC3 c.2149–1G>A is a founder pathogenic variant, (2) describe the phenotype and clinical characteristics of mutation carriers and (3) compare these patients with those with the most frequent pathogenic HCM variants: MYBPC3 p.Arg502Trp/Gln.MethodsWe reviewed genetic tests performed in HCM probands at our institution. We carried out transcript analyses to demonstrate the splicing effect, and haplotype analyses to support the founder effect of MYBPC3 c.2149–1G>A. Carriers with this mutation were compared with those from MYBPC3 p.Arg502Trp/Gln in terms of presentation features, imaging and outcomes.ResultsMYBPC3 c.2149–1G>A was identified in 8 of 570 probands and 25 relatives. Penetrance was age and sex dependent, 50.0% of the carriers over age 36 years and 75.0% of the carriers over 40 years showing HCM. Penetrance was significantly higher in males: in carriers older than 30 years old, 100.0% of males vs 50.0% of females had a HCM phenotype (p=0.01). Males were also younger at diagnosis (32±13 vs 53±10 years old, p<0.001). MYBPC3 c.2149–1G>A resulted in an abnormal transcript that led to haploinsufficiency and was segregated in two haplotypes. However, both came from one founder haplotype. Affected carriers showed a better functional class and higher left ventricular ejection fraction (LVEF) than patients with MYBPC3 p.Arg502Trp/Gln (p<0.05 for both). Nevertheless, the rate of major adverse outcomes was similar between the two groups.ConclusionsMYBPC3 c.2149–1G>A splicing variant is a founder mutation. Affected males show an early onset of HCM and with higher penetrance than women. Carriers show better functional class and higher LVEF than MYBPC3 p.Arg502Trp/Gln carriers, but a similar rate of major adverse outcomes.

It has been demonstrated previously that clinical phenotypes of HCM (hypertrophic cardiomyopathy) caused by mutations in the cardiac MyBP-C (myosin-binding protein C) gene show late onset, low penetrance and favourable clinical course. However, we have encountered severe phenotypes in several carriers of the MyBP-C gene mutations. The aim of the present study was to screen novel MyBP-C gene mutations in patients with HCM and to investigate the genetic differences in affected subjects with severe phenotypes. The MyBP-C gene was screened in 292 Japanese probands with HCM, and a novel c.2067+1G→A mutation was present in 15 subjects in five families. Clinical phenotypes of carriers of the c.2067+1G→A mutation were compared with those of a previously identified Arg820Gln (Arg820→Gln) mutation in the MyBP-C gene. The disease penetrance in subjects aged ≥30 years was 90% in carriers of the c.2067+1G→A mutation and 61% in carriers of the Arg820Gln mutation. Sudden death occurred in four subjects from three families with the c.2067+1G→A mutation and in two subjects from one family with the Arg820Gln mutation. Two carriers of the c.2067+1G→A mutation had substantial hypertrophy (maximal wall thickness ≥30 mm). In contrast, two carriers of the Arg820Gln mutation had end-stage HCM. In conclusion, the c.2067+1G→A mutation is associated with HCM with substantial hypertrophy and moderate incidence of sudden death, whereas the Arg820Gln mutation is associated with end-stage HCM. These observations may provide important prognostic information regarding the clinical practice of HCM.

Myosin 1g (Myo1g) is a mechanoenzyme associated with actin filaments, expressed exclusively in hematopoietic cells, and involved in various cellular functions, including cell migration, adhesion, and membrane trafficking. Despite the importance of Myo1g in distinct functions, there is currently no monoclonal antibody (mAb) against Myo1g. mAbs are helpful tools for the detection of specific antigens in tumor cells and other tissues. The development of mAbs against targeted dysregulated molecules in cancer cells remains a crucial tool for aiding in the diagnosis and the treatment of patients. Using hybridoma technology, we generated a panel of hybridomas specific for Myo1g. ELISA, immunofluorescence, and Western blot assay results revealed the recognition of Myo1g by these novel monoclonal antibodies in normal and transformed T and B cells. Here, we report the development and application of new monoclonal antibodies against Myo1g for their potential use to detect its overexpression in acute lymphoblastic leukemia (ALL) patients.

Abstract Class I myosins regulate diverse aspects of locomotion, vesicular traffic, and peripheral process architecture in amoeba and in mammalian cells. Mass spectrometric analysis of lymphocyte fractions enriched for plasma membrane/microvilli identified myosin 1G (Myo1G) as abundant and enriched from human peripheral blood T-cells and Myo1G plus Myo1C as abundant and enriched from a mouse pre-B-cell line. To understand its structure and function, we have investigated Myo1G by immunofluorescence, by immunoblot, by transfection of wt and mutant constructs and by creation of a knockout mouse. Myo1G is abundant in multiple hematopoietic lineages, but absent in most other cell types. Endogenous Myo1G is highly enriched at the plasma membrane and in microvilli/ruffles of lymphocytes (as is transfected Myo1G in Jurkat T-cells). Structure-function analysis with truncation and point mutants show that Myo1G localization at the membrane, like Myo1C, requires a conserved "PH-like" domain present in the tail. But unlike Myo1C, it also depends on presence of its actin-binding motor domain. Knockout mice have no obvious defect in hematopoietic cell development. However preliminary studies shown that there are defects in activation of splenic T cells after stimulation with anti TCR. Studies are in progress to elucidate the underlying mechanism by which Myo1G contributes to T-cell activation.

It has been demonstrated that a long-term stay in hypergravity (HG: 2G) modified the phenotype and the contractile properties of rat soleus muscle. The ability of this muscle to contract was drastically reduced, which is a sign of anticipated aging. Consequently, our aim was to determine whether rats conceived, born, and reared in hypergravity showed adaptative capacities in normogravity (NG: 1G). This study was performed on rats divided into two series: the first was reared in HG until 100 days and was submitted to normogravity until 115 to 220 postnatal days (HG-NG rats); the second was made up of age paired groups reared in normogravity (NG rats). The contractile, morphological, and phenotypical properties of soleus muscle were studied. Our results showed that the NG rats were characterized by coexpressions of slow and fast myosin, respectively, 76.5 and 23.5% at 115 days. During their postnatal maturation, the fast isoform was gradually replaced by slow myosin. At 220 days, the relative proportions were respectively 91.05% and 8.95%. From 115 to 220 days, the HG-NG rats expressed 100% of slow myosin isoform and they presented a slower contractile behavior compared with their age-matched groups; at 115 days, the whole muscle contraction time was increased by 35%, and by 15%, at 220 days. Our study underlined the importance of gravity in the muscular development and suggested the existence of critical periods in muscle phenotype installation.

L'asymétrie Droite-Gauche (DG) fait référence au placement asymétrique des organes par rapport à la ligne médiane du corps. Des dérèglements de l'établissement de l'asymétrie DG au cours du développement peuvent conduire à des organes mal placés - une situation qui peut être mortelle.J'utilise le poisson zèbre pour étudier les mécanismes qui établissent l'asymétrie DG. Chez le poisson, un organe cilié - la vésicule de Kupffer (KV) agit comme Organisateur central de l'asymétrie DG (ODG). Le ligand nodal Southpaw (Spaw) et son antagoniste Dand5 sont initialement exprimés de manière symétrique autour de l'ODG. Le battement de cils dans l'ODG établit un flux directionnel qui réprime Dand5 à gauche, permettant à Spaw de se propager à gauche par auto-induction et de diriger ainsi la latéralité du cœur, du cerveau et des viscères.Contrairement à de nombreux vertébrés, la drosophile établit l'asymétrie DG indépendamment de cils en utilisant un remodelage cellulaire chiral contrôlé par la myosine Myo1D. Notre groupe a montré précédemment que chez le poisson zèbre Myo1D régule l'asymétrie DG en orientant les cils de la KV pour permettre la formation du flux de fluide brisant la symétrie. En plus de myo1d, le génome du poisson zèbre code pour le gène étroitement apparenté myo1g. L'objectif de ma thèse a été d'étudier l'importance de Myo1G pour l'établissement de l'asymétrie DG.La KV agit comme un ODG central contrôlant la latéralité de différents organes. En conséquence, les mutants myo1d qui ont un flux de l'ODG altéré présentent des défauts DG au niveau du cœur, du cerveau et des viscères. En revanche les mutants myo1g présentent des anomalies DG dans le cœur et le cerveau, mais pas dans les viscères, ce qui suggère que myo1g exerce une fonction indépendante du flux.Pour tester directement cette hypothèse j'ai inactivé myo1g chez des mutants dnaaf1 dépourvus de motilité ciliaire et ne présentant donc pas de flux de l'ODG. Alors que le mouvement asymétrique des précurseurs cardiaques est randomisé vers le côté gauche ou droit chez les simple mutants dnaaf1, le mouvement asymétrique des cellules précurseurs est totalement perdu dans des double mutants myo1g ; dnaaf1, démontrant que myo1g fonctionne effectivement indépendamment du flux ciliaire.Mon travail révèle que Myo1G est nécessaire pour le transfert de l'information de latéralité de l'ODG vers les différents tissus cibles par la Spaw. Chez les mutants myo1g, l'expression de Spaw reste limitée à la partie postérieure de l'embryon ce qui permet d'établir correctement la latéralité des viscères postérieurs, alors que le cœur et le cerveau antérieurs ne parviennent pas à établir la latéralité.Spaw se lie à un complexe de récepteurs formé par Acvr2, Alk4 et le co-récepteur Oep. Les interactions ligand/récepteur déclenchent la phosphorylation des facteurs de transcription Smad2/3, qui sont ensuite transportés dans le noyau pour activer les gènes cible. La transduction du signal Nodal induit Spaw lui-même (qui se propage donc par auto-induction) ainsi que son antagoniste Lefty1.Lorsque j'ai injecté des quantités égales d'ARN de Spaw et évalué l'activation de lefty1, les mutants myo1g ont affiché une réponse plus faible que les animaux WT, indiquant ainsi une altération de la transduction du signal Nodal. En revanche, un variant constitutivement activé de Smad2 produit des réponses équivalentes chez les deux types d'animaux.Des études antérieures ont impliqué les Myosine1 dans le transport subcellulaire de récepteurs TGFβ. Différentes voies d'endocytose favorisent la transduction du signal ou au contraire, déclenchent la dégradation des récepteurs. Mes travaux montrent que les mutants myo1g présentent une diminution du nombre d'endosomes positifs aux récepteurs de Spaw, suggérant ainsi que Myo1G pourrait réguler l'asymétrie LR en contrôlant le trafic des récepteurs TGFβ
Left-Right (LR) asymmetry refers to the asymmetric placement of organs across the midline. Dysregulation of LR asymmetry establishment during animal development can lead to misplaced organs - a situation that can be lethal.I use zebrafish as a model to study the mechanisms that establish LR asymmetry. In zebrafish, a ciliated organ - Kupffer's Vesicle (KV) acts as a central LR organizer (LRO). The Nodal ligand Southpaw (Spaw) and its antagonist Dand5 are initially expressed in a symmetric fashion around the LRO. The beating of cilia in the LRO establishes a directional fluid flow that represses Dand5 on the left, allowing Spaw to spread on the left side through auto-induction and thereby direct the laterality of heart, brain and viscera.In contrast to many vertebrates, Drosophila establishes LR asymmetry independently of cilia using chiral cell remodeling controlled by the unconventional Myosin Myo1D. Our group showed previously that zebrafish Myo1D regulates LR asymmetry by orienting KV cilia and promoting the formation of a symmetry-breaking fluid flow. In addition to myo1d, the zebrafish genome encodes the closely related gene myo1g. The objective of my PhD work has been to study the contribution of Myo1G to the establishment of zebrafish LR asymmetry.KV acts as a central LRO that controls the laterality of the different organs of the animal. Accordingly, myo1d mutants that have an altered LRO flow present LR defects at the level of the heart, brain and viscera. In contrast, myo1g mutants present LR defects in heart and brain but not viscera, suggesting that myo1g may exert a flow-independent function in LR asymmetry.In order to directly test this hypothesis, I inactivated myo1g in dnaaf1 mutants which lack ciliary motility and present therefore no LRO flow. While the asymmetric movement of cardiac precursors is randomized to either the left or right side in dnaaf1 single mutants, asymmetric precursor cell movement is altogether lost in myo1g ; dnaaf1 double mutants, demonstrating thereby that myo1g functions indeed independently of the LRO flow.My work reveals that in contrast to Myo1D which regulates LRO cilia orientation, Myo1G is required for the Nodal-mediated transfer of laterality information from the central LRO to different target tissues. In myo1g mutants, spaw expression remains limited to the posterior of the embryo, properly guiding the laterality establishment of the posterior viscera, whereas the anterior heart and brain fail to establish laterality.In the context of the establishment of Zebrafish LR asymmetry, the Nodal ligand Spaw binds to a receptor complex formed by Acvr2, Alk4 and the co-receptor Oep. Productive ligand/receptor interactions trigger the phosphorylation of the downstream transcription factors Smad2/3, which then translocate into the nucleus to activate downstream genes. Nodal signal transduction induces spaw itself (which therefore propagates through auto-induction) as well the Nodal antagonist lefty1.When I injected equal amounts of spaw mRNA in WT and myo1g mutants and assessed the response by monitoring lefty1 activation, myo1g mutant embryos displayed a weaker response to spaw overexpression than their WT siblings, indicating thereby an impairment in Nodal signal transduction. In contrast, misexpression of constitutively activated smad2 produced equivalent responses in WT and myo1g mutant animals.Of particular interest, previous studies have implicated Myosin1 proteins in the endocytic trafficking of TGFβ receptor molecules. Different endocytic pathways have been shown to either promote TGFβ receptor signal transduction or conversely trigger receptor degradation. My work shows that myo1g mutants present a decrease in the number of Nodal-receptor positives endosomes, suggesting thereby that Myo1G may regulate LR asymmetry by controlling TGFβ receptor trafficking