Differential Brain-Region Specific Roles of CASK in Optic Nerve Hypoplasia and Pontocerebellar Hypoplasia

项目总结 了解中枢神经系统(CNS)的不同区域如何受到遗传侮辱的影响是至关重要的 促进对中枢神经系统病理的研究，这些疾病在美国构成了主要的公共卫生负担。这个 在大多数情况下，小脑和视神经是两个不成比例发育不良的区域。 人类的木桶基因突变。CASK是一种神秘的多结构域支架蛋白，它扮演着至关重要的 通过与活动区蛋白质和蛋白质的相互作用在突触前组织蛋白质复合体中的作用 跨突触黏附分子，如Liprs-α和Neurexins。X连锁CASK基因突变的研究 在半合子状态下，人类在出生后大部分是致命的，并导致小头畸形症，桥和 杂合突变的小脑发育不良(PCH)和视神经发育不良(ONH)。 虽然木桶传统上被认为在中枢神经系统的发育中发挥作用，但最近的数据表明 它在成人中枢神经系统的维持中继续发挥作用。具体地说，CaskIn的急性全局删除 使用Creer-Tamoxifen系统的成年小鼠导致运动协调能力进行性退化 在注射他莫昔芬几个月后达到严重共济失调。这与进步不谋而合。 小脑大体形态恶化。因此，这提供了一个了解 基因在成体中枢神经系统功能中的持续作用，以前被认为是发育重要的 这一功能在特定地区的方式可能有何不同。 最近已经证明，在木桶丢失的背景下，ONH的进展是非细胞的 在本质上是自主的，因为从视网膜神经节细胞中删除CASK本身并不会加剧ONH，但 从视神经的纤维星形胶质细胞中删除它确实会加剧ONH。但是，当删除木桶时 特别是在使用Calb2启动子驱动的Cre重组酶的颗粒细胞(GC)中，似乎有一种细胞- 大哥大的自主死亡。这提供了一个机会来检查潜在的病因和功能 在相同的基因侮辱下，两个地区的损失是不同的。AS颗粒细胞是血管紧张素转换酶的主要兴奋性驱动力。 小脑，这个项目将研究颗粒细胞丢失的进展，颗粒细胞丢失与 功能性运动障碍和共济失调以及主要兴奋性驱动因素缺失的电生理学意义 在一个孤立的大脑区域。此外，该项目将阐明尖峰计时和频率上的异常 在小脑中，浦肯野细胞在解剖上颗粒细胞数量减少之前或之后。该项目将 在显示ONH但不显示ONH的模型中，还要检查视觉功能是否与视神经直径相关 利用来自视觉皮质和背侧的V1的视觉诱发电位记录进行PCH和反之亦然 丘脑的膝状核。最后，这项研究将确定非凋亡性或 细胞凋亡性死亡是GCs缺失的基础。因此，这项研究将调查不同的原因和功能 在以CASK缺失为测试案例的单一遗传侮辱的背景下，具有区域特异性的后果。

PROJECT SUMMARY Understanding how different regions of the central nervous system (CNS) are affected by genetic insults is critical to advancing the study of CNS pathologies which present a major public health burden in the United States. The cerebellum and optic nerve are two such regions that are disproportionately hypoplastic in the majority of cases of CASK gene mutation in humans. CASK is an enigmatic multi-domain scaffolding protein which plays a vital role in organizing protein complexes at the pre-synapse through interactions with both active zone proteins and trans-synaptic adhesion molecules such as liprins-α and neurexins. Mutations in the X-linked CASK gene in humans are largely post-natally lethal in the hemizygous condition and result in microcephaly with pontine and cerebellar hypoplasia (PCH) as well as optic nerve hypoplasia (ONH) in heterozygous mutations. While CASK has been traditionally regarded as playing a role in CNS development, recent data indicate that it plays a continued role in the maintenance of the adult CNS. Specifically, acute global deletion of Cask in adult mice using a CreER-Tamoxifen system leads to progressive degeneration in motor coordination culminating in profound ataxia several months after tamoxifen injection. This coincides with a progressive deterioration of cerebellar gross morphology. Thus, this presents a unique opportunity to understand the continued role of a gene, previously regarded as developmentally important, in the function of the adult CNS and how this function may differ in a region-specific manner. Recently, it has been demonstrated that progression of ONH in the context of CASK-loss is non-cell autonomous in nature as deleting Cask from retinal ganglion cells themselves does not exacerbate ONH, but deleting it from fibrous astrocytes of the optic nerve does exacerbate ONH. However, when Cask is deleted specifically in granule cells (GCs) using a Calb2 promoter driven Cre recombinase, there appears to be a cell- autonomous death of GCs. This provides an opportunity to examine how underlying etiopathology and functional loss differ in two regions given the same genetic insult. As granule cells are the major excitatory driver of the cerebellum, this project will investigate the progression of granule cell loss, the correlation of granule cell loss to functional motor loss and ataxia, and the electrophysiological implications of loss of the major excitatory driver in an isolated brain region. Further, the project will elucidate whether aberrations in spike-timing and frequency among cerebellar Purkinje cells precede or follow anatomical reductions in granule cell number. The project will also examine whether visual function correlates to optic nerve diameter in models which display ONH but not PCH and vice versa using visual evoked potential recordings from V1 of visual cortex and the dorsal lateral geniculate nucleus of the thalamus. Finally, the study will determine molecular mechanisms of non-apoptotic or apoptotic cell death underlying loss of GCs. Thus, the study will investigate differing causes and functional consequences with region-specificity in the context of a single genetic insult using Cask deletion as a test-case.