Genetic Analysis of Roof Plate Function in the CNS

描述(由申请人提供)： 我们正在研究小鼠的背侧中枢神经系统模式的形成，作为人类先天性脑畸形的一个范例，基于这样的假设，即小鼠和人类的畸形背后有类似的图案缺陷。格局形成是用来描述发展过程中出现的空间生物组织的术语。人类中枢神经系统背侧中线畸形是一种鲜为人知的先天性缺陷，包括某些形式的无前脑畸形和巨脑畸形。这两种畸形主要是背侧皮质的畸形。小脑背侧中线畸形的一个例子是Dandy-Walker畸形。顶板是胚胎中枢神经系统中一种特殊的背中线结构。它是发育中的脊髓背侧模式信息的重要调节器，通过分泌的分子指导背侧感觉中间神经元的规范和分化。我们假设，屋顶板在大脑更前部的水平上发挥着类似的功能。具体地说，我们假设LIM同源结构域编码基因LMX 1a和LMX 1b是中枢神经前部正常顶板发育所必需的，这些基因的缺失会导致顶板功能的丧失，并随后导致发育中的小脑和皮质中相邻神经元的异常指定和分化。我们先前已经证明，自发的神经系统突变小鼠Dreher含有LMX 1a基因突变，并且LMX 1a是小鼠中枢神经系统顶板发育所必需的。在Dreher脊髓中，不会产生顶板。因此，在Dreher脊髓中，邻近的背侧感觉中间神经元的规格、模式和分化都是异常的。在发育中的中枢神经系统的前部水平，Dreher鼠仍存在残留的顶板，这表明大脑中的顶板具有不同的发生机制。这项建议利用基因打靶和转基因技术，结合广泛的表型分析，研究LMX 1a和密切相关的基因LMX 1b在发育中的小脑和大脑皮层附近顶板的形成和功能中的作用。

DESCRIPTION (provided by applicant): We are studying dorsal CNS pattern formation in the mouse, as a paradigm for human congenital brain malformations based on the hypothesis that similar patterning defects underlie mouse and human malformations. Pattern formation is the term used to describe the emergence of spatial biological organization during development. Malformations of the dorsal midline of the human CNS are poorly understood congenital defects that include some forms of holoprosencephaly and megalencephaly. Both of these are primarily malformations of the dorsal cortex. An example of a dorsal midline malformation of the cerebellum is Dandy-Walker Malformation. The roof plate is a specialized dorsal midline structure in the embryonic CNS. It is a crucial regulator of dorsal patterning information in the developing spinal cord, directing the specification and differentiation of dorsal sensory interneurons via secreted molecules. We hypothesize that the roof plate performs a similar function in more anterior levels in the brain. Specifically, we hypothesize that the Lim-homeodomain encoding genes, Lmx 1a and Lmx 1b are required for normal roof plate development in the anterior CNS and that loss of these genes leads to loss of roof plate function and subsequent abnormal specification and differentiation of adjacent neurons in the developing cerebellum and cortex. We have previously demonstrated that the spontaneous neurological mouse mutant, dreher, harbors mutations in the Lmx 1a gene and that Lmx 1a is required for roof plate development in the mouse CNS. In the dreher spinal cord, no roof plate is generated. Consequently, the specification, patterning and differentiation of adjacent dorsal sensory interneurons are abnormal in the dreher spinal cord. At anterior levels of the developing CNS, a residual roof plate is still present in dreher mice, suggesting that roof plate in the brain has a different mechanism of genesis. This proposal makes use of gene targeting and transgenic technology in combination with extensive phenotypic analysis to examine the roles of Lmx 1a and the closely related gene, Lmx 1b, in roof plate formation and function adjacent to the developing cerebellum and cerebral cortex.