Translational Regulation in Adult Neural Stem Cells

描述（由申请人提供）：“干细胞研究为治疗一系列无法治愈的先天性、发育性、精神病或退行性疾病提供了巨大的潜力（NIH PA-04-101）。然而，彻底了解调节成体神经干细胞（NSC）增殖和分化的分子机制是其治疗应用的先决条件。干细胞领域的进展扩大了我们对成体神经干细胞功能转录调控的认识。近年来，microRNA（miRNA）通路在干细胞的增殖和分化中发挥重要作用，表明成体神经干细胞的翻译调控在成体神经干细胞的功能中即使不是更重要，也是同等重要的。本项目的长期目标是了解翻译调控在成人神经发生中的作用。脆性X智力低下蛋白（FMRP）是脆性X综合征中丢失的蛋白质，是一种选择性RNA结合蛋白，与多聚核糖体形成信使核糖核蛋白（mRNP）复合物。FMRP调节蛋白质翻译，并且FMRP的缺失导致选择性mRNA的异常翻译、树突棘的延迟成熟和神经元中的异常微管稳定性。我们发现FMRP在成人脑神经干/祖细胞（NSPCs）中也高度表达。本课题组和其他研究小组的研究表明，FMRP与miRNA通路中的Dicer和Argonaute蛋白等组分之间存在生物化学和遗传学上的相互作用，提示成年NSCs中特定mRNA的翻译调控可能是通过miRNA通路与FMRP之间的协同作用实现的。我们已经从野生型（野生型）和Fmr 1敲除（KO）成年小鼠中分离了NSPCs，并且发现FMRP的缺失影响体外成年NSPCs的增殖和命运特异性。我们推测成体神经干细胞的增殖和分化在翻译水平上受到miRNA途径和RNA结合蛋白FMRP的调控。因此，我们建议：首先确定NSPC特异性mRNA的翻译是否受miRNA调节（Aim 1）;然后确定成体NSC的翻译调节是否对体内NSC功能至关重要（Aim 2）;最后确定FMRP和miRNA途径是否协同调节成体NSC的增殖和分化（Aim 3）。我们的工作将由在成人神经发生方面具有专业知识的PI赵博士和在翻译调控和miRNA方面具有丰富经验的Co-PI金博士共同努力进行。这项工作的结果将增加一个新的层面，我们的知识，神经干细胞的调节在成人大脑。我们的前提是，更好地了解这些调节机制是成人神经干细胞治疗人类疾病的先决条件。

DESCRIPTION (provided by applicant): "Stem cell research offers enormous potential for treating a host of congenital, developmental, psychiatric or degenerative diseases for which there are no cures (NIH PA-04-101)." However, a thorough understanding of the molecular mechanisms that regulate adult neural stem cell (NSC) proliferation and differentiation is a pre-requisite for their therapeutic applications. Advances in the stem cell field have expanded our knowledge of transcriptional regulations in adult NSC functions. Recently, microRNA (miRNA) pathway has been shown to play important roles in the proliferation and differentiation of stem cells, indicating that translational regulation of adult NSCs, though less understood, is equally, if not more important in adult NSC function. The long-term goal of this project is to understand the role of translational regulation in adult neurogenesis. Fragile X mental retardation protein (FMRP), the protein that is lost in Fragile X syndrome, is a selective RNA-binding protein that forms a messenger ribonucleoprotein (mRNP) complex associating with polyribosomes. FMRP regulates protein translation and the loss of FMRP leads to abnormal translation of selective mRNAs, delayed maturation of dendritic spines, and abnormal microtubule stability in neurons. We found that FMRP is also highly expressed in neural stem/progenitor cells (NSPCs) derived from adult brains. Our recent studies and those of other groups have demonstrated the biochemical and genetic interactions between FMRP and the components of the miRNA pathway, including Dicer and Argonaute proteins, suggesting that translational regulation of specific mRNAs in adult NSCs could be achieved by collaborative actions between miRNA pathway and FMRP. We have isolated NSPCs from both wild type (wildtype) and Fmr1 knockout (KO) adult mice, and found that the loss of FMRP affects both proliferation and fate- specification of adult NSPCs in vitro. We hypothesize that the proliferation and differentiation of adult NSCs is regulated at the translational level by miRNA pathway and RNA binding protein, FMRP. Therefore, we propose: first to determine whether the translation of NSPC-specific mRNAs is regulated by miRNAs (Aim 1); then to determine whether translational regulation of adult NSCs is critical for NSC function in vivo (Aim 2); and finally to determine whether FMRP and miRNA pathway collaboratively regulate the proliferation and differentiation of adult NSCs (Aim 3). Our proposed work will be carried out by combining the efforts of the PI, Dr. Zhao, who has expertise in adult neurogenesis, and the Co-Pi, Dr. Jin, who has extensive experience in translational regulation and miRNA. The outcome of this work would add a new dimension to our knowledge of NSC regulation in the adult brain. It is our premise that a better understanding of these regulatory mechanisms is a pre-requisite for the therapeutic application of adult NSCs for human diseases.