Genetic and Molecular Studies of Neurogenesis

描述(申请人提供)：我们正在研究胚胎发育期间中枢神经系统(CNS)是如何组装的。这对美国国立卫生研究院的任务有几个潜在的人类健康益处。首先，许多神经疾病的治疗将受益于一种从患者自己的诱导多能干细胞(IPS)中产生特定类型神经元的方法。其次，许多精神疾病部分是由发育缺陷引起的。开发治疗工具来治疗这些类型的疾病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，这对于发现哺乳动物相关的神经发生机制具有深远的重要意义。目前关于神经前体细胞如何获得其空间同一性(如前脑和后脑)的了解很多，但我们仍然对它们如何顺序产生不同类型的细胞知之甚少。我们之前发现了一系列转录因子，这些转录因子在果蝇神经系统中指定了时间特性。在这里，我们集中在胚胎前体细胞(目标1-3)中的三个相关问题，并以第一次对新发现的果蝇胚胎后神经前体细胞的时间同一性的分析结束，该细胞与灵长类外室区祖细胞具有相同的特征(目标4)。在目标1中，我们将确定驼背转录因子是在祖细胞中瞬时作用，还是在有丝分裂后神经元中持续作用，以确定“第一个出生”的时间身份。由于哺乳动物的驼背同源基因Ikaros在决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，这一目标有可能帮助设计治疗方法，以取代对人类视觉至关重要的一种细胞类型。在目标2中，我们对前一个资助期的结果进行了跟踪，结果显示，随着时间的推移，神经前体细胞失去了形成早期出生的神经元亚型的能力，以响应驼背表达的脉冲。我们将通过鉴定一种核蛋白来确定这些祖细胞“渐进性丧失能力”的机制，这种核蛋白的表达模拟能力窗口，其延长的表达可以延长能力窗口。在目标3中，我们开始研究一种新的“II型”神经干细胞，这是我们和其他人最近发现的。每个脑叶含有8个II型神经母细胞，它们不对称分裂，产生一系列“中间神经前体细胞(INP)，每个INP也不对称分裂，形成一个10-12个神经元的序列。我们将描述神经母细胞或INP出生顺序与不同神经亚型产生的关系。我们最近发现了在INP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特性。 公共卫生相关性：拟议的项目与公共卫生相关，因为了解单个前体细胞如何整合空间和时间线索以生成独特的神经元亚型，将有助于指导干细胞治疗，以取代因创伤性脑损伤(TBI)、中风、疾病或年龄相关性退化而失去的神经元。因此，这项拟议的研究与美国国立卫生研究院的使命有关，该使命是为了减少普遍存在的环境和遗传性大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.