先天性骨骼肌疾病如肢体发育畸形、骨骼肌营养不良等在新生儿中发病率高、难以治愈，患者生命受到严重威胁。胚胎骨骼肌的生成依赖于骨骼肌干细胞（MuSC）分化，但其转录调控机制未明。我们前期研究已完整绘制了人类胚胎肢体早期发育的单细胞图谱，通过进一步构建骨骼肌分化调控网络，我们发现转录因子MSC是调控MuSC分化的关键节点。体外预实验表明：MSC在胚胎MuSC及新生肌纤维中维持高表达水平；MSC在原代MuSC中被敲减可增强骨骼肌干性基因表达、促进骨骼肌生成，并诱导未知靶基因MTUS2高表达。据此我们推测，MSC是调控胚胎MuSC分化的关键转录抑制因子。本项目拟进一步通过MSC在体表达及体外MuSC分化研究体系，深入探讨MSC靶向MTUS2抑制胚胎MuSC分化的调控作用及关键机理。项目将阐明人胚胎MuSC分化的转录调控新机制，为理解骨骼肌发育及骨骼肌疾病的诊断治疗提供重要的科学依据。

Congenital skeletal muscle diseases such as limb malformations and muscular dystrophy are severe threats to health in newborns due to the high morbidity rate and restricted clinical therapeutics. Embryonic muscle stem cells (MuSC), the primary contributors to myogenesis, drive skeletal muscle formation during the whole embryo developmental process. Despite a lot of work on model organisms, the key questions regarding human embryonic MuSC differentiation remain elusive. Our recent project has built a single-cell transcriptional landscape of human hind limb development. In constructing the MuSC regulatory network, we identified MSC as a pivotal node by connecting with numbers of target genes. In vitro experiments further indicated that: MSC was highly expressed in MuSCs and newly formed muscle fibers; knocked-down of MSC improved MuSC stemness, promoted differentiation and extremely induced expression of the unknown target gene MTUS2. With all above evidences, we hypothesize that MSC acts as a key transcriptional inhibitor in regulating embryonic MuSC differentiation. In this project, we aim to further explore the detailed mechanisms of myogenic regulation guided by MSC through targeting MTUS2 with in vivo and in vitro experimental systems. We expect the findings of our work will provide new insights for the knowledge of skeletal muscle development as well as for studying limb developmental disorders.