LIM-HD/bHLH Combinatorial Code in Motoneurons

运动神经元中的 LIM-HD/bHLH 组合代码

• 批准号: 7413938
• 负责人: Soo-Kyung Lee
• 金额: $ 41.17万
• 依托单位: BAYLOR COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-04-01 至 2011-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7413938
• 关键词: BHLH Protein; Binding; Binding Sites; Biochemical; Boxing; Cells; Code; DNA; Disease; Embryo; Gene Expression; Gene Targeting; Genes; Genomics; Goals; Heart; Helix-Turn-Helix Motifs; Interneurons; Knowledge; LIM Domain; Link; Mediating; Methods; Molecular; Molecular Genetics; Motor Neurons; Mus; Nervous system structure; Neuraxis; Neuroglia; Neuronal Injury; Neurons; Nodal; Nuclear; Numbers; Organ; Pancreas; Pituitary Gland; Play; Property; Prosencephalon; Retina; Role; Screening procedure; Specific qualifier value; Spinal; Spinal Cord; System; Testing; To specify; base; cell type; cofactor; combinatorial; homeodomain; insight; novel; response; transcription factor; yeast genetics

Our long-term goal is to understand the combinatorial transcriptional regulatory networks in the developing central nervous system (CMS), which play essential roles to specify a large number of distinct neuronal and glial cell types. LIM homeodomain (LIM-HD) and basic helix-loop-helix (bHLH) proteins are relatively well characterized transcription factors regulating cell type specification in the embryonic CMS. However, both the molecular mechanism by which these factors regulate gene expression and the identity of their target genes remain poorly understood. We wish to explore these important issues by specifically focusing on their role in generating spinal motoneurons (MNs). Our results demonstrate that LIM-HD factors Lhx3 and Isl1specify two distinct neurons of the embryonic spinal cord in a combinatorial manner. Lhx3 and the LIM cofactor NLI(for nuclear LIM-interactor) form a V2-interneuron (IN)-specifying tetramer. In contrast, Lhx3 and NLI form a MN-specifying hexamerwhen coexpressed with Isl1. During MN specification, bHLH proteins Ngn2/NeuroM are functionally synchronized with the hexamer, although the molecular mechanism underlying this novel crosstalk is not fully understood. Our recent screening effort led to the finding of genomic fragments with the NLI:lsl1 :Lhx3 hexamer binding sites, many of which are linked to candidate MN genes. These results led to our central hypothesis of this proposal: the hexamer directly regulates multiple MNgenes in conjunction with bHLH factors to effect MN specification. We will dissect this hypothesis to uncover the molecular basis that directs MN specification in response to a combinatorial expression of transcription factors. Specifically, studies are proposed to explore the diverse functional aspects of the hexamer/bHLHs with their candidate target genes. Overall, the proposed studies should provide critical insights into the basic principles for the proper formation of the nervous system and practical information to treat a variety of neuronal injuries and diseases. Of note, LIM-HD/bHLH factors are also involved with specifying cell fates in other regions of the developing CNS (e.g., retina and forebrain) as well as non-CNS organs such as heart, pancreas and pituitary, which highlights the general importance of the proposed studies.

我们的长期目标是了解发展中国家的组合转录调控网络 中枢神经系统（CMS），它在指定大量不同的神经元和 神经胶质细胞类型。 LIM 同源域 (LIM-HD) 和碱性螺旋-环-螺旋 (bHLH) 蛋白相对较好 表征了胚胎 CMS 中调节细胞类型规范的转录因子。然而，两者 这些因子调节基因表达的分子机制及其靶基因的身份 仍然知之甚少。我们希望通过特别关注这些重要问题在 产生脊髓运动神经元（MN）。我们的结果表明 LIM-HD 因子 Lhx3 和 Isl1 指定 以组合方式形成胚胎脊髓的两个不同的神经元。 Lhx3 和 LIM 辅因子 NLI（用于 核 LIM 相互作用物）形成 V2 中间神经元 (IN) 特异性四聚体。相比之下，Lhx3 和 NLI 形成 与 Isl1 共表达时的 MN 特异性六聚体。在 MN 规范过程中，bHLH 蛋白 Ngn2/NeuroM 在功能上与六聚体同步，尽管这种新颖的分子机制 串扰尚未完全理解。我们最近的筛选工作发现了基因组片段 NLI:lsl1 :Lhx3 六聚体结合位点，其中许多与候选 MN 基因相关。这些结果导致我们 该提案的中心假设：六聚体与 bHLH 结合直接调节多个 MN 基因 影响 MN 规范的因素。我们将剖析这个假设，以揭示指导的分子基础 MN 规范响应转录因子的组合表达。具体来说，研究是 建议探索六聚体/bHLH 及其候选靶基因的多种功能。 总的来说，拟议的研究应该为正确形成的基本原则提供批判性的见解。 神经系统和治疗各种神经元损伤和疾病的实用信息。值得注意的是， LIM-HD/bHLH 因子还与发育中枢神经系统其他区域的细胞命运有关（例如， 视网膜和前脑）以及非中枢神经系统器官，如心脏、胰腺和垂体，这突出了 拟议研究的一般重要性。