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

项目摘要 了解中枢神经系统（CNS）的不同区域如何受到遗传损伤的影响至关重要 促进中枢神经系统病理学的研究，这在美国是一个主要的公共卫生负担。的 小脑和视神经是两个这样的区域，在大多数情况下不成比例地发育不全 人类CASK基因突变。CASK是一种神秘的多结构域支架蛋白， 通过与活性区蛋白质的相互作用在突触前组织蛋白复合物中的作用， 跨突触粘附分子，如liprins-α和neurexins。X连锁CASK基因突变 在半合子状态下，人类在出生后大部分是致命的， 小脑发育不全（PCH）以及视神经发育不全（ONH）的杂合突变。 虽然CASK传统上被认为在CNS发育中发挥作用，但最近的数据表明， 它在维持成人中枢神经系统中起着持续的作用。具体地，在小鼠中急性全局删除Cask。 使用CreER-他莫昔芬系统的成年小鼠导致运动协调的进行性退化 在他莫昔芬注射后几个月达到严重的共济失调。这与一个渐进的 小脑大体形态学恶化。因此，这提供了一个独特的机会来了解 一个基因在成人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， 这一功能在特定区域可能有何不同。 最近，已经证明在CASK丢失的背景下ONH的进展是非细胞性的。 由于从视网膜神经节细胞中删除Cask本身不会加剧ONH， 将其从视神经的纤维性星形胶质细胞中去除确实会加重ONH。然而，当木桶被删除时， 特别是在使用Calb 2启动子驱动的Cre重组酶的颗粒细胞（GC）中，似乎存在细胞- GC的自动死亡。这提供了一个机会，以检查潜在的病因和功能 在相同的遗传损伤下，两个地区的损失不同。由于颗粒细胞是主要的兴奋性驱动程序， 小脑，本项目将研究颗粒细胞损失的进展，颗粒细胞损失与 功能性运动丧失和共济失调，以及主要兴奋性驱动因子丧失的电生理学意义 在一个孤立的大脑区域。此外，该项目将阐明是否畸变尖峰时间和频率 小脑浦肯野细胞之间的差异在颗粒细胞数量解剖减少之前或之后。该项目将 还检查了在显示ONH但不显示ONH的模型中，视功能是否与视神经直径相关。 用V1视皮层和背外侧的视觉诱发电位记录PCH和反之亦然 丘脑的膝状体核。最后，这项研究将确定非凋亡或 凋亡性细胞死亡是GC丧失的基础。因此，该研究将调查不同的原因和功能 结果与区域特异性的背景下，一个单一的遗传损伤使用木桶删除作为测试案例。

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.