Genetic Mechanisms in Cerebellum Malformations

描述（由申请人提供）：小脑正常发育的中断导致临床显著的畸形，其机制基础尚不清楚。本研究结合现有的和新兴的遗传学和基因组学方法，在一种类似Dandy-Walker畸形的新小鼠模型中解剖小脑蚓畸形的分子机制。nur12突变的纯合子显示蚓部和脉络膜丛几乎完全发育不全，第四脑室囊性扩张，后颅窝内小脑结构前旋不良。作为确定与该突变体和人类患者之间共有特征相关的分子机制的初步数据，申请人已经确定了nur12突变体中锌指转录的零突变。申请人已开始确定该突变的发育后遗症，包括对神经祖细胞增殖的深刻影响。三个具体目标将：(1)在基因座上建立等位基因系列，并研究零等位基因严重程度（半球参与）的个体间差异的来源；(2)通过原位标记、标记基因分析和培养信号响应测量相结合，确定nur12畸形的细胞和发育机制，包括BMP/SMAD和EBF信号通路的作用测试；(3)利用高度平行的转录因子结合全基因组定位分析平台，通过序列发育阶段的转录谱分析，鉴定ZFP423、bmp激活的SMADs和EBF因子之间启动子占用的重叠，确定ZFP423活性在小脑发育中的分子靶点。相关性：该提案将确定与Dandy-Walker畸形相关的机制，这是一种严重的缺陷，在1/25,000 -1/30,000的新生儿中发现。初步结果表明，在这里作用的机制影响前体细胞继续分裂的能力，这可能在产前诊断的畸形和儿童脑癌的治疗应用。

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.