Mechanical Signaling mediated 3D chromatin remodeling in stem cell fate

骨骼肌组织驻留干细胞，又称卫星细胞，在骨骼肌组织的修复和再生中起着至关重要的作用。成体SC处于不分裂的静止状态。在肌肉损伤后，干细胞迅速退出静止、激活、增殖和分化，形成新的肌肉。再生过程中的失败会导致肌肉疾病，如营养不良、椎板病变和衰老。最初从静止到激活的转变是促进肌肉组织再生的关键一步。将静止的干细胞转化为活跃的分裂干细胞的分子驱动因素在很大程度上是未知的。这些静止和激活的机制依赖于组织特异性转录因子、染色质重构体和高阶染色质组织来调节组织特异性基因的表达。本实验室的长期目标是研究高阶染色质结构对SC静止状态的影响，进而确定激活命运。该建议的目的是确定WNT4/RhoA(机械信号)介导的3D染色质重塑在干细胞命运中的作用。在这里，我们的中心假设是WNT4-RhoA信号通路调节细胞核和染色质的动力学，从而影响骨骼肌干细胞的命运和细胞的黏附和迁移过程。中心假说将通过三个特定的目的来验证：1)确定WNT4-RhoA信号通路如何调节SCs中YAP的表达。2)确定WNT4-RhoA信号通路在染色质重塑中的作用，从而影响SC的命运。3)探讨核层蛋白A/C结合细胞核形态和大小与细胞过程的机制。这一建议是创新的，因为我们正在寻找1)非规范的WNT4-RhoA细胞骨架信号通路与静止期SCs染色质重塑之间的新的未探索的联系，2)YAP1与激活SCs基因组格局的重塑，以及3)Lamin AC在SCs黏附和迁移中的功能作用。了解染色质的高阶结构并确定调节染色质景观的分子，使其能够在静止和激活之间转换，将对在各种肌肉病理和衰老中改善组织再生的治疗具有重要影响。

Skeletal muscle tissue resident stem cells, also called Satellite cells, play a vital role in the repair and regeneration of skeletal muscle tissue. The adult SCs exist in a non-dividing quiescent state. Upon muscle injury, the SCs rapidly exit quiescence, activate, proliferate and differentiate to form new muscle. A failure in the regenerative process results in muscle diseases such as dystrophies, laminopathies and aging. The initial transition from quiescence to activation represents a critical step to enhance regeneration of the muscle tissue. The molecular drivers that transform the quiescent SCs into actively dividing stem cells is largely unknown. These mechanisms of quiescence and activation rely on tissue specific transcription factors, chromatin remodelers and higher order chromatin organization to modulate tissue specific gene expression. The long-term goal of my laboratory is to study the influence of higher order chromatin structure on SC quiescence to activation fate determination. The objective of this proposal is to determine the Wnt4/RhoA (mechanical signaling) mediated 3D chromatin remodeling in stem cell fate. Here, our central hypothesis is Wnt4-RhoA signaling pathway regulates nuclear and chromatin dynamics, thereby influencing skeletal muscle stem cell fate and cellular processes of adhesion and migration. The central hypothesis will be tested by three specific aims: 1) Determine how Wnt4 -RhoA signaling pathway regulates the expression of YAP in SCs. 2) Determine the role of Wnt4-RhoA signaling pathway on chromatin remodeling, thereby affecting SC fate. 3) Explore the mechanism by which nuclear Lamin A/C couples nuclear shape and size with cellular processes. This proposal is innovative, as we are pursuing novel unexplored links between 1) the non-canonical Wnt4-RhoA cytoskeletal signaling pathway and chromatin remodeling in quiescent SCs, 2) YAP1 and remodeling of the genomic landscape in activated SCs, and 3) the functional role of Lamin AC in adhesion and migration of SCs. Understanding the higher order chromatin structure and identifying the molecules that regulate the chromatin landscape enabling the transition between quiescence and activation, will have a significant impact on therapeutically improving tissue regeneration in various muscle pathologies and in aging.