Transcriptional control of growth plate chondrocytes

项目总结 生长板是高度专业化的软骨结构，确保骨骼生长和软骨内 胎儿和出生后发育过程中的骨化。它们由软骨细胞形成和维持，如 这些细胞遵循空间和时间上严格控制的多步分化程序。现在 该项目的重点是转录因子，这些转录因子在影响这一计划中起着关键作用，但其模式 行动仍然没有完全被破译。它将检验范式转换假设，即SOX9，它的辅助因素 SOX5和SOX6，以及RUNX2和RUNX3以协作的方式完成它们的许多主要功能。这 假说基于坚实的科学前提，包括生长板中这些因素的共同表达 软骨细胞，SOX9结合的许多软骨细胞特异性增强子中存在矮小结构域基序， 初步证据表明，SOX和RUNX蛋白在增强子激活中具有协同活性。 具体目的1是确定SOX5/6、SOX9和RUNX2/3在生长板过程中是否存在遗传相互作用 在小鼠胚胎中形成和在幼年小鼠中维持活跃的生长板。具体目标2是 在生长板软骨细胞中分析SOX5/6、SOX9和RUNX2/3的全部基因靶体，并 评估和验证它们的重叠。具体目标3是确定SOX5/6、SOX9和 运行2/3的协作性。这些蛋白质将被测试在诱导染色质可及性方面的作用，以及三个- 维度连通性，以及DNA结合和招募功能伙伴的协作性。新的 这些发现应该会对目前对管理 生长板和其他软骨类型的形成和维持。因此，他们应该有助于揭开 多种病理类型的分子基础，包括软骨发育不良、肿瘤和关节退行性变 疾病，并为这些仍然不能令人满意的治疗方法提出新的、创新的和有效的治疗方法 疾病。

PROJECT SUMMARY Growth plates are highly specialized cartilage structures that ensure skeletal growth and endochondral ossification during fetal and postnatal development. They are formed and maintained by chondrocytes, as these cells follow a spatially and temporally tightly controlled multi-step differentiation program. The present project focuses on transcription factors that have pivotal roles in effecting this program, but whose modes of actions remain incompletely deciphered. It will test the paradigm-shifting hypothesis that SOX9, its cofactors SOX5 and SOX6, and RUNX2 and RUNX3 fulfill many of their main functions in a cooperative manner. This hypothesis is based on a solid scientific premise that includes co-expression of the factors in growth plate chondrocytes, the presence of RUNT-domain motifs in many chondrocyte-specific enhancers bound by SOX9, and preliminary evidence that the SOX and RUNX proteins have synergistic activities in enhancer activation. Specific Aim 1 is to determine whether SOX5/6, SOX9 and RUNX2/3 genetically interact during growth plate formation in mouse fetuses and in the maintenance of active growth plates in juvenile mice. Specific Aim 2 is to profile the whole genetic targetomes of SOX5/6, SOX9 and RUNX2/3 in growth plate chondrocytes, and to assess and validate their overlap. Specific Aim 3 is to identify mechanisms underlying SOX5/6, SOX9 and RUNX2/3 cooperativity. The proteins will be tested for roles in inducing chromatin accessibility and three- dimensional connectivity, and for cooperativity in DNA binding and recruitment of functional partners. New findings should have a significant impact on current understanding of fundamental mechanisms governing the formation and maintenance of growth plates and other cartilage types. They should thereby help uncover the molecular basis of many types of pathologies, including chondrodysplasias, tumors and joint degenerative diseases, and also suggest novel, innovative and efficient treatments for these still unsatisfactorily treatable diseases.