Genetic Mechanisms in Cerebellum Malformations

描述(由申请人提供)：小脑正常发育的障碍会导致临床上显著的畸形，其机制基础尚不清楚。这一建议结合了现有的和新兴的遗传学和基因组方法，在一个类似Dandy-Walker畸形的新小鼠模型中剖析了小脑蠕虫畸形的分子机制。Nur12基因突变的纯合子表现为蚯蚓和脉络丛几乎完全发育不全，第四脑室囊性扩张，以及后颅窝内小脑结构的前部旋转不良。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，申请人已经在Nur12突变体中发现了锌指转录的零突变。申请人已经开始确定这种突变的发育后遗症，包括对神经前体细胞增殖的深远影响。这三个特定目标将(1)建立该基因座上的等位基因系列，并调查无效等位基因严重程度(半球受累)的个体间差异来源；(2)确定Nur12畸形的细胞和发育机制，包括通过结合原位标记、标记基因分析和培养上的信号反应测量来测试BMP/SMAD和EBF信号通路的作用；以及(3)通过在发育的连续阶段进行转录谱分析，以及利用高度平行的转录因子结合分析平台，确定ZFP423在小脑发育中活性的分子靶点。相关性：这项提案将确定与丹迪-沃克畸形相关的机制--一种在25,000-30,000名新生儿中发现的严重缺陷。初步结果表明，在此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童脑癌都有治疗应用。

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.