Understanding CTCF boundaries controlling Hox gene expression

理解控制HOX基因表达的CTCF边界 摘要 基因表达的时空调控对多细胞疾病的发展至关重要 有机体。尽管增强子和转录之间的环状相互作用的变化开始 SITES是公认的基因调控模式，更大的3D基因组的贡献 基因表达和正常发育的重组在很大程度上是模糊的。我们建议 阐明CTCF转录因子如何控制HOX染色质结构的实验 集群，以确保适当的HOX基因表达，从而，身体模式。 在胚胎发育过程中，HOX基因的精确表达指导细胞识别 它们在身体轴上的相对位置。HOX基因被组织成四个簇，与个体 这些簇中的基因表达模式在空间和时间上与 它们的实际染色体组织。HOX基因在脊髓中的共线表达 控制运动神经元(MN)亚型，从而控制它们的连接性。在MN分化过程中， HOX团簇经历了染色质和三维重组，从一个被抑制的状态变成两个 含有转录或抑制基因的结构域。这两种染色质状态是 由边界的CTCF结合绝缘，保持继承的稳定的HOX染色质状态 通过发展以确保适当的MN连接。重要的是，我们最近展示了 在胚胎发育过程中，CTCF边界对于正常的身体模式是必不可少的 在活体内。了解CTCF如何在HOX保持染色质和3-D边界的绝缘 我们提出的集群：1)了解如何破坏CTCF介导的染色质边界 影响脊髓MN亚型同一性；2)确定建立MNS亚型的分子基础 CTCF依赖的边界；3)高级蛋白质组学研究，以确定所需的因子 染色质相关CTCF的绝缘体活性，强调那些相互作用是 依赖于RNA。

Understanding CTCF boundaries controlling Hox gene expression Summary Spatial and temporal control of gene expression is crucial for the development of multicellular organisms. Although changes in looping interactions between enhancers and transcription start sites is an acknowledged mode of gene regulation, the contribution of larger 3D genomic reorganizations to gene expression and normal development is largely obscure. We propose experiments to clarify how the CTCF transcription factor controls chromatin structure at the Hox clusters to ensure proper Hox gene expression and thus, body patterning. During embryonic development, precise expression of Hox genes instructs cells to recognize their relative position in body axes. Hox genes are organized in four clusters with individual genes in these clusters expressed in patterns that are spatially and temporally collinear with their physical chromosomal organization. Collinear Hox gene expression along the spinal cord controls motor neuron (MN) subtypes and thus their connectivity. During MN differentiation, the Hox clusters undergo a chromatin and 3-D reorganization from a single repressed state to two domains harboring either transcribed or repressed genes. The two chromatin states are insulated by CTCF binding at the boundary, maintaining stable Hox chromatin states inherited though development to ensure proper MN connectivity. Of relevance, we recently demonstrated that the CTCF boundary is essential to normal body patterning during embryonic development in vivo. To understand how CTCF maintains insulated chromatin and 3-D boundaries at Hox clusters we propose: 1) To understand how disrupting the CTCF-mediated chromatin boundary affects subtype identity of spinal MNs; 2) To determine the molecular basis of establishing a CTCF-dependent boundary; 3) An advanced proteomics study to identify factors required by chromatin associated CTCF for its insulator activity, emphasizing those whose interaction is RNA-dependent.