Rôle du facteur de transcription « Odd-skipped-related 1 » (Osr1) dans le contrôle de la formation du muscle via le tissu conjontif

The musculoskeletal system allows body motion. Despite the distinct mesodermal origins of its components, the development of muscle, connective tissue (CT) and bone is highly coordinated. Osr1 encodes a zinc-finger transcription factor expressed in muscle CT in limbs. The aim of the PhD was to elucidate Osr1 function in the non-cell autonomous regulation of mouse limb muscle formation. Genetic lineage tracing revealed that Osr1+ cells are progenitors for several CTs, including muscle, dermal and lung CTs, but also for smooth muscle and brown adipocytes. Comprehensive phenotypic analysis of skeletal muscles in E13.5 Osr1GCE/GCE mouse embryos revealed impaired muscle formation. Transcriptomic analysis highlighted two major molecular characteristics caused by the lack of Osr1 activity. First, Osr1 actively repressed the expression of genes associated with cartilage and tendon development, suggesting that Osr1 confers a muscle connective tissue identity. Second, Osr1 positively regulated the expression of components of the extracellular matrix (ECM). In addition to the decrease of ECM components, numerous signaling molecules were significantly down-regulated in Osr1-deficient cells of mutant embryos. This highlights the function of Osr1+ resident connective tissue cells in limb muscle formation. It also establishes that Osr1 regulates the transcription of ECM components in limb muscle CT. Lastly, it suggests that Osr1 exerts its function via chemokines and secreted factors to ensure proper muscle development.Le système musculo-squelettique permet la mobilité. Le développement des muscles, du tissu conjonctif (TC) et des os est coordonné de manière très précise. Osr1 encode pour un facteur de transcription qui est exprimé au niveau du TC musculaire au cours du développement. Le but de cette thèse est d'élucider la fonction d’Osr1 dans la régulation cellulaire non-autonome de la formation des muscles au niveau des membres dans le modèle murin. Le traçage génétique a révélé que les cellules Osr1+ sont à l’origine de plusieurs TC, y compris musculaire, cutané et pulmonaire, mais aussi à l’origine du muscle lisse et des adipocytes bruns. L’analyse phénotypique des embryons de souris Osr1GCE/GCE à E13.5 a révélé des défauts dans l’organisation des muscles. L’analyse transcriptomique montre deux caractéristiques moléculaires causées par le manque d'activité d’Osr1. Tout d'abord, Osr1 réprime l'expression de gènes associés au développement du cartilage et du tendon, ce qui suggère qu’Osr1 confère une identité «tissu conjonctif musculaire». Ensuite, Osr1 régule positivement l'expression des composants de la matrice extracellulaire (MEC). De plus, l’expression de nombreuses molécules de signalisation est diminuée dans les cellules déficientes pour Osr1. Ces résultats montrent l’importance des cellules Osr1+ du TC dans la formation des muscles des membres. Ces résultats montrent également qu’Osr1 régule la transcription des composants de la MEC au niveau du tissu conjonctif musculaire. Enfin, ils suggèrent qu’Osr1 exerce sa fonction par l'intermédiaire de facteurs sécrétés pour assurer le bon développement musculaire

Biallelic variants in ADAMTS15 cause a novel form of distal arthrogryposis

Purpose: We aimed to identify the underlying genetic cause for a novel form of distal arthrogryposis. Methods: Rare variant family-based genomics, exome sequencing, and disease-specific panel sequencing were used to detect ADAMTS15 variants in affected individuals. Adamts15 expression was analyzed at the single-cell level during murine embryogenesis. Expression patterns were characterized using in situ hybridization and RNAscope. Results: We identified homozygous rare variant alleles of ADAMTS15 in 5 affected individuals from 4 unrelated consanguineous families presenting with congenital flexion contractures of the interphalangeal joints and hypoplastic or absent palmar creases. Radiographic investigations showed physiological interphalangeal joint morphology. Additional features included knee, Achilles tendon, and toe contractures, spinal stiffness, scoliosis, and orthodontic abnormalities. Analysis of mouse whole-embryo single-cell sequencing data revealed a tightly regulated Adamts15 expression in the limb mesenchyme between embryonic stages E11.5 and E15.0. A perimuscular and peritendinous expression was evident in in situ hybridization in the developing mouse limb. In accordance, RNAscope analysis detected a significant coexpression with Osr1, but not with markers for skeletal muscle or joint formation. Conclusion: In aggregate, our findings provide evidence that rare biallelic recessive trait variants in ADAMTS15 cause a novel autosomal recessive connective tissue disorder, resulting in a distal arthrogryposis syndrome. (C) 2022 The Authors. Published by Elsevier Inc. on behalf of American College of Medical Genetics and Genomics.US National Institute of Neurological Disorders and Stroke [R35 NS 105078]; US National Human Genome Research Institute (NHGRI); National Heart, Lung, and Blood Institute [UM1 HG006542, R01 GM106373, U01 HG011758, 512848]; Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) of the National Institutes of Health [P50HD103555]; International Rett Syndrome Foundation (IRSF) [3701-1]; NHGRI [K08 HG008986]; German Research Council (DFG) [KO 2891/9-1]; BIH Center for Regenerative Therapies (BCRT)We are grateful to the families for their participation in this study. We thank Aris. N. Economides and Manuel Holtgrewe for their valuable suggestions and support. J.R.L. laboratory is supported by the US National Institute of Neurological Disorders and Stroke (R35 NS 105078) and in part by the US National Human Genome Research Institute (NHGRI) and National Heart, Lung, and Blood Institute to the Baylor-Hopkins Center for Mendelian Genomics (BHCMG; UM1 HG006542), the National Institute of General Medical Sciences (NIGMS; R01 GM106373), the NHGRI Baylor College of Medicine Genomics Research Elucidates Genetics of Rare Diseases (BCM-GREGoR; U01 HG011758), the Muscular Dystrophy Association (512848), and the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) of the National Institutes of Health under award number P50HD103555 for use of the Clinical Translation Core facilities. D.P. is supported by International Rett Syndrome Foundation (IRSF; grant #3701-1). J.E.P. was supported by NHGRI K08 HG008986. U.K. obtained funding from the German Research Council (DFG)(KO 2891/9-1) and the BIH Center for Regenerative Therapies (BCRT)(cross-field project GenoPro)