Genetic and Molecular Studies of Neurogenesis

描述（由申请人提供）：我们正在研究中枢神经系统（CNS）在胚胎发育期间是如何组装的。这对NIH的使命有几个潜在的人类健康益处。首先，许多神经系统疾病的治疗将受益于从患者自身的诱导多能干（IPS）细胞产生特定类型的神经元的方法。第二，许多精神障碍部分源于发育缺陷。产生治疗这些类型的疾病的治疗工具将需要详细了解每种神经元亚型通常是如何形成的。我们一直在模式生物果蝇中研究这个问题，这对发现哺乳动物神经发生相关机制非常重要。目前我们对神经祖细胞如何获得空间身份（例如前脑与后脑）了解很多，但我们对它们如何连续产生不同的细胞类型仍然知之甚少。我们以前确定了一系列的转录因子，指定果蝇神经系统内的时间身份。在这里，我们集中在胚胎祖细胞（目标1-3）的三个相关问题，并结束与新发现的果蝇胚胎后神经祖细胞，与灵长类动物的外脑室区祖细胞（目标4）共享功能的时间身份的第一次分析。 在目标1中，我们将确定驼背转录因子是否在祖细胞中短暂或连续地在有丝分裂后的神经元中起作用，以指定“第一个出生的”时间身份。由于哺乳动物驼背直系同源物Ikaros在指定早期出生的视网膜神经节细胞命运方面具有类似的作用，因此这一目标有可能帮助设计治疗方法来取代人类视觉所必需的细胞类型。 在目标2中，我们跟踪了上一个资助期的结果，这些结果表明神经祖细胞随着时间的推移失去了形成早期神经元亚型的能力，以响应Hunchback表达的脉冲。我们将确定在这些祖细胞中的“能力逐渐丧失”的机制，通过鉴定其表达模拟能力窗口的核蛋白来辅助，并且其延长的表达可以延长能力窗口。 在目标3中，我们启动了我们和其他人最近发现的一种新的“II型”神经干细胞的研究。每个脑叶包含8个II型神经母细胞，它们不对称分裂产生一系列“中间神经祖细胞”（INPs），每个INPs也不对称分裂产生一系列10-12个神经元。我们将描述成神经细胞或INP出生顺序和不同神经亚型的产生之间的关系。我们最近确定了在INPs中顺序表达的转录因子，我们将确定它们是否在这些亚系中指定时间身份。 公共卫生相关性：拟议的项目与公共卫生有关，因为了解单个祖细胞如何整合空间和时间线索以产生独特的神经元亚型将有助于指导干细胞治疗，以取代因创伤性脑损伤（TBI），中风，疾病或年龄相关变性而失去的神经元。因此，拟议的研究与NIH的使命有关，即减轻普遍的环境和遗传性脑疾病给社会带来的负担。

DESCRIPTION (provided by applicant): We are investigating how the central nervous system (CNS) is assembled during embryonic development. This is has several potential human health benefits relevant to the NIH mission. First, the treatment of many neurological disorders would benefit from a method for generating specific types of neurons from the patient's own induced pluripotent stem (IPS) cells. Second, many psychiatric disorders arise in part from developmental defects. Generating therapeutic tools to treat these types of disorders will require a detailed understanding of how each neuronal subtype is normally formed. We have been investigating this question in the model organism Drosophila, which has been profoundly important for discovering mechanisms of neurogenesis relevant in mammals. Much is currently known about how neural progenitors acquire their spatial identity (e.g. forebrain vs. hindbrain) but we still know very little about how they sequentially produce different cell types. We previously identified a series of transcription factors that specify temporal identity within the Drosophila nervous system. Here we focus on three related questions in embryonic progenitors (Aims 1-3) and conclude with the first analysis of temporal identity in a newly discovered Drosophila post- embryonic neural progenitor that shares features with the primate outer ventricular zone progenitor (Aim 4). In Aim 1, we will determine whether the Hunchback transcription factor acts transiently in progenitors or continuously in post-mitotic neurons to specify "first-born" temporal identity. Because the mammalian Hunchback ortholog Ikaros has a similar role in specifying early-born retinal ganglion cell fates, this aim has the potential to hep design therapeutic treatments to replace a cell type essential for human vision. In Aim 2, we follow up on results from the previous funding period showing that neural progenitors lose competence over time to form early-born neuron subtypes in response to a pulse of Hunchback expression. We will determine the mechanism of "progressive loss of competence" in these progenitors, aided by the identification of a nuclear protein whose expression mimics the competence window, and whose prolonged expression can extend the competence window. In Aim 3, we initiate work on a new "Type II" neural stem cell that we and others recently discovered. Each brain lobe contains 8 type II neuroblasts that divide asymmetrically to produce a series of "intermediate neural progenitors (INPs) that each also divide asymmetrically to make a sequence of 10-12 neurons. We will characterize the relationship between neuroblast or INP birthorder and the production of distinct neural subtypes. We have recently identified transcription factors expressed in sequentially in INPs, and we will determine if they specify temporal identity in these sublineages. PUBLIC HEALTH RELEVANCE: The proposed project is relevant to public health because understanding how spatial and temporal cues are integrated by single progenitors to generate unique neuronal subtypes will help guide stem cell therapy for replacing neurons lost to traumatic brain injury (TBI), stroke, disease, or age-related degeneration. Thus, the proposed research is relevant to NIH's mission to reduce the burden to society arising from prevalent environmental and genetic brain disorders.