Cell cycle control in the mammalian retina

描述（由申请人提供）：某些人类基因的突变导致中枢神经系统（CNS）特定区域的细胞数量缺陷。这些变化导致发育异常，严重损害中枢神经系统功能。有证据表明，其中一些突变发生在调节细胞增殖的基因中。然而，人们对它们起作用的机制知之甚少。为了解决这个问题，我们正在研究小鼠视网膜发育过程中增殖的调控。发育中的小鼠视网膜是研究中枢神经系统发育的良好模型系统，并且已经确定了导致视网膜神经上皮特异性增殖缺陷的基因突变。确定这些突变如何改变视网膜增殖可能有助于我们了解整个中枢神经系统神经上皮细胞如何发生区域特异性增殖调节。Chx10是一种在视网膜祖细胞中表达的同源盒基因，无突变可导致人和小鼠的先天性小眼症。在视网膜中，细胞数量严重不足，这在很大程度上是由于发育过程中增殖的减少。两个细胞周期基因Cyclin D1和p27（Kip1）在Chx10突变视网膜中被错误调控，p27（Kip1）的基因失活可显著恢复细胞数量，减轻小眼症的严重程度。这些发现建立了Chx10与视网膜祖细胞细胞周期之间的联系。

DESCRIPTION (provided by applicant): Mutations in certain human genes cause cell number defects in specific regions of the central nervous system (CNS). These changes cause developmental anomalies that severely compromise CNS function. Evidence is starting to emerge that several of these mutations are in genes that regulate proliferation. However, the mechanisms by which they function are poorly understood. To address this, we are studying the regulation of proliferation during murine retinal development. The developing mouse retina is well established as a model system for studying CNS development, and genetic mutations have been identified that cause proliferation defects specific to the retinal neuroepithelium. Identifying how these mutations alter retinal proliferation may help us to understand how region specific regulation of proliferation occurs throughout the CNS neuroepithelium. Chx10 is a homeobox gene expressed in retinal progenitor cells and null mutations cause congenital microphthalmia in humans and mice. In the retina, there is a severe deficit in cell number, and this is due in large part to a reduction in proliferation during development. Two cell cycle genes, Cyclin D1 and p27(Kip1), are misregulated in the Chx10 mutant retina, and genetic inactivation of p27(Kip1) significantly restores cell number and alleviates the severity of the microphthalmia. These findings establish a link between Chx10 and the cell cycle in retinal progenitor cells. Our hypothesis is that Chx10 could have multiple functions in retinal progenitor proliferation. In Aim 1 we will determine if Chx10 regulates proteins required for G 1 progression. In Aim 2, we will determine which phases of the cell cycle are dependent on Chx10. For these Aims, Chx10 null mice will be mated with mice containing null alleles of critical cell cycle genes to produce combinatorial mutants. In Aim 3, we will determine if Chx10 is required for mitogen signaling in retinal progenitor cells using primary cell culture. These studies have the potential to identify the functions of Chx10 in regulating retinal progenitor proliferation, and this information can be applied to other areas of the CNS where proliferation is a key determinant of development and function.