Understanding CTCF boundaries controlling Hox gene expression

理解控制Hox基因表达的CTCF边界 总结 基因表达的时空调控对于多细胞生物的发育至关重要。 有机体尽管增强子和转录之间的循环相互作用开始发生变化， 位点是公认的基因调控模式，较大的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。我们提出 实验以阐明CTCF转录因子如何控制Hox上的染色质结构， 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 它们在身体轴线上的相对位置。Hox基因被组织成四个簇， 这些簇中的基因表达的模式在空间和时间上与 他们的染色体结构Hox基因沿脊髓沿着共线表达 控制运动神经元（MN）亚型，从而控制它们的连接。在MN分化期间， Hox簇经历了染色质和3-D重组，从单一的抑制状态到两个 包含转录或抑制基因的区域。这两种染色质状态是 通过CTCF在边界处的结合而绝缘，维持遗传的稳定Hox染色质状态 虽然开发以确保适当的MN连接。与此相关的是，我们最近证明了 CTCF边界对胚胎发育期间的正常身体模式至关重要 in vivo.为了了解CTCF如何在Hox保持绝缘染色质和3-D边界， 我们提出：1）为了了解如何破坏CTCF介导的染色质边界 影响脊髓MN的亚型身份; 2）确定建立脊髓MN的分子基础， CTCF依赖的边界; 3）先进的蛋白质组学研究，以确定所需的因素， 染色质相关CTCF的绝缘子活性，强调那些相互作用是 RNA依赖性。

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.