bHLH Transcription Factors in Neural Development

描述(由申请人提供)：越来越多的大脑疾病与偏离通常仔细校准的兴奋性和抑制性神经元活动之间的平衡有关。建立这种抑制性/兴奋性神经元平衡的关键选择点是由转录因子Ptf1a控制的。Ptf1a是一种bHLH转录因子，是背侧脊髓、小脑和视网膜中GABA能抑制神经元所必需的。在缺乏Ptf1a的情况下，神经前体细胞不能产生抑制性神经元，并异常地呈现兴奋性神经元表型。揭示Ptf1a表达的转录控制及其下游靶点的功能将为调节中枢神经系统多个区域的神经回路的发育过程提供分子洞察力。由于PTf1a功能的时机和机制，它为揭示神经元分化和神经元亚型规范的分子机制提供了一个独特的机会。对Ptf1a基因座顺式调控序列的鉴定表明，在细胞分化为抑制性神经元的过程中，可分离的元件控制转录的启动、自我调节、对dI4/dil前体的限制和下调。此外，Ptf1a的直接靶点已被确定为在抑制兴奋性神经元识别的同时介导抑制性神经元识别的候选靶点。当前项目的目标是在这些发现的基础上，1)识别通过顺式调控序列调节Ptf1a的反式作用上游因子和信号通路，以及2)确定Ptf1a下游靶标在背角、小脑和视网膜中指定的中间神经元的功能。这一计划的成功将影响对干细胞/祖细胞如何转变为成熟细胞类型并产生电路形成所需的神经元多样性的理解。识别引导细胞沿特定谱系向下的路径可能在干细胞操作和神经疾病的治疗中具有治疗价值。

DESCRIPTION (provided by applicant): An increasing number of diseases of the brain are being linked to deviations from the normally carefully calibrated balance between excitatory and inhibitory neuronal activities. A critical choice point for establishing this inhibitory/excitatory neuronal balance is governed by the transcription factor Ptf1a. Ptf1a is a bHLH transcription factor that is required for GABAergic inhibitory neurons in the dorsal spinal cord, cerebellum, and retina. In the absence of Ptf1a, neural progenitor cells fail to generate inhibitory neurons and aberrantly assume an excitatory neuronal phenotype. Uncovering the transcriptional control of Ptf1a expression and the function of its downstream targets will provide molecular insight into developmental processes regulating the neuronal circuitry in multiple regions of the central nervous system. Because of the timing and the mechanism of PTf1a function, it provides a unique opportunity to uncover the molecular mechanisms that couple neuronal differentiation and neuronal subtype specification. Identification of cis-regulatory sequences in the Ptf1a gene locus revealed separable elements controlling transcription initiation, autoregulation, restriction to dI4/dIL progenitors, and downregulation as the cells differentiate to inhibitory neurons. In addition, direct targets of Ptf1a have been identified that serve as candidates for mediating inhibitory neuronal identity while suppressing excitatory neuron identity. The goal of the current project is to build on these findings to 1) identify trans-acting upstream factors and signaling pathways that function through the cis-regulatory sequences to regulate Ptf1a, and 2) determine the function of a downstream target of Ptf1a in specification of interneurons in the dorsal horn, cerebellum, and retina. Success in this program will impact understanding of how stem/progenitor cells transition to mature cell types and generate the neuronal diversity required for circuit formation. Identifying the pathways that direct cells down a specific lineage may have therapeutic value in stem cell manipulation and treatment of neurological disorders.