Genetic Mechanisms in Cerebellum Malformations

描述（由申请方提供）：小脑正常发育中断导致临床显著畸形，其机制基础尚不清楚。该提案使用了一个新的小鼠模型类似Dandy-Walker畸形的建立和新兴的遗传和基因组方法的组合来解剖小脑蚓部畸形的分子机制。nur 12突变的纯合子显示几乎完全的小脑蚓部和脉络丛发育不全，第四脑室囊性扩张，以及后颅窝内小脑结构的前旋转不良。作为用于定义与该突变体和人类患者之间共有的特征相关的分子机制的初步数据，申请人已经鉴定了nur 12突变体中锌指转录的无效突变。申请人已开始鉴定该突变的发育后遗症，包括对神经祖细胞增殖的深远影响。这三个具体目标是：（1）在该位点建立等位基因系列，并调查严重程度的个体间变异来源（半球受累）无效等位基因;（2）通过原位标记、标记基因分析和细胞培养信号反应测定等方法，明确nur 12畸形的细胞和发育机制，包括BMP/SMAD和EBF信号通路的作用;和（3）通过在发育的连续阶段的转录谱分析和通过使用用于转录因子结合的全基因组位置分析的高度平行平台鉴定ZFP 423、BMP-活化的SMAD和EBF因子之间的启动子占据的重叠来鉴定ZFP 423活性在小脑发育中的分子靶标。相关性：该提案将确定与Dandy-Walker畸形相关的机制-这是一种在1/25，000 - 1/30，000出生中发现的严重缺陷。初步结果表明，在这里起作用的机制影响前体细胞继续分裂的能力，这可能对产前诊断的畸形和儿科脑癌都有治疗应用。

DESCRIPTION (provided by applicant): Disruptions in the normal development of the cerebellum result in clinically significant malformations whose mechanistic bases are poorly understood. This proposal uses a combination of established and emerging genetic and genomic methods to dissect molecular mechanisms of cerebellar vermis malformation in a new mouse model resembling Dandy-Walker malformations. Homozygotes for the nur12 mutation show show nearly complete agenesis of the vermis and choroid plexus, cystic dilation of the fourth ventricle, and anterior malrotation of cerebellar structures within the posterior fossa. As preliminary data for defining molecular mechanisms relevant to features shared between this mutant and human patients, the applicant has identified a null mutation of a zinc finger transcription in nur12 mutants. The applicant has begun to identify developmental sequelae to this mutation, including profound effects on proliferation of neural progenitor cells. The three specific aims will (1) establish an allelic series at the locus and investigate sources of interindividual variation in the severity (hemispheric involvement) of null allele; (2) define cellular and developmental mechanisms of the nur12 malformation, including tests for the roles of BMP/SMAD and EBF signaling pathway, through a combination of in situ labeling, marker gene analyses and signaling response measurements in culture; and (3) identify molecular targets of ZFP423 activity in cerebellum development by transcriptional profiling at sequential stages of development and by identifying overlaps in promoter occupancy among ZFP423, BMP-activated SMADs and EBF factors using a highly parallel platform for genome-wide location analysis for transcription factor binding. Relevance: This proposal will identify mechanisms relevant to the Dandy-Walker malformation - a severe defect found in 1/25,000 -1/30,000 births. Preliminary results suggest that the mechanisms acting here affect the ability of precursor cells to continue dividing, which may have therapeutic application for both prenatally diagnosed malformations and pediatric brain cancers.