Developmental Mechanisms of the Chromodomain Gene Chd7

这些研究对于提高我们对发育缺陷的理解有直接的意义 与Chd 7缺乏有关。基因表达的精确调控对正常发育至关重要 大多数组织和器官。染色体结构域蛋白，以DNA结合和ATP依赖性为特征 解旋酶结构域在染色质重塑中的作用知之甚少，并发挥表观遗传影响 对基因表达的影响在人类中，CHD 7的单倍不足，CHD 7是第三个亚家族的成员， chromodomain蛋白，导致CHARGE综合征。CHARGE是一种多重异常障碍 其特征在于眼部缺损、心脏缺陷、软骨闭锁、生长迟缓， 发育、生殖器发育不全和耳畸形，包括耳聋和前庭疾病。我们 产生基因捕获无效等位基因（Chd 7 Gt/+）杂合的小鼠。这些老鼠表现出许多特征 与人类CHARGE表型相似，包括严重的内耳缺陷和出生后生长迟缓。 Chd 7 Gt/+小鼠也在Chd 7阳性组织中表达半乳糖苷酶报告基因，可用于 追踪Chd 7缺陷细胞的命运CHARGE在人类和小鼠中的临床特征如下： 可变和不完全的渗透，和最常见的发育畸形，在这两个人类 CHD 7功能缺失的小鼠为半规管发育不全或发育不全。内耳缺损伴 chd 7缺乏的小鼠是复杂的，包括半规管和神经支配的畸形。 感觉上皮细胞。特定的组织和细胞类型似乎对Chd 7剂量唯一敏感，但 细胞Chd 7表达模式和Chd 7缺陷在细胞增殖，分化， 生存是未知的。此外，CHD 7相互作用的伙伴和下游目标在耳朵和 神经细胞没有被表征。这些知识将有助于指导治疗的合理发展， 内耳缺陷我们的总体假设是，CHD 7在转录复合体中起作用，抑制或 激活发育中的耳和神经组织中的下游靶基因。我们有三个具体目标： (1)表征Chd 7突变小鼠中的细胞增殖、存活和分化， (2)确定CHD 7表达组织对内耳发育的贡献， (3)表征来自野生型和Chd 7突变胚胎的培养的内耳和神经干细胞，并使用 以确定CHD 7是否直接结合候选靶基因的启动子。 拟议的实验结果将带来新的见解染色质的基本过程 重塑和转录调控。更好地理解组织特异性要求， Chd 7还可提高CHARGE相关性内耳及其他疾病的诊断和治疗水平。 发育缺陷

These studies have direct relevance for improving our understanding of the developmental defects associated with Chd7 deficiency. Precise regulation of gene expression is critical for normal development of most tissues and organs. Chromodomain proteins, characterized by DNA binding and ATP-dependent helicase domains, have poorly understood roles in chromatin remodeling and exert epigenetic influences on gene expression. In humans, haploinsufficiency for CHD7, a member of the third subfamily of chromodomain proteins, causes CHARGE syndrome. CHARGE is a multiple anomaly disorder characterized by ocular coloboma, heart defects, atresia of the choanae, retarded growth and development, genital hypoplasia, and ear anomalies including deafness and vestibular disorders. We generated mice heterozygous for a gene trapped null allele (Chd7Gt/+). These mice exhibit many features similar to human CHARGE phenotypes, including severe inner ear defects and postnatal growth delays. Chd7Gt/+ mice also express a ¿-galactosidase reporter in Chd7-positive tissues, and can be used for tracking the fates of Chd7 deficient cells. The clinical features of CHARGE in humans and mice are variable and incompletely penetrant, and the most common developmental malformation in both humans and mice with loss of CHD7 function is semicircular canal dysgenesis or hypoplasia. Inner ear defects with Chd7 deficiency in mice are complex, and include malformations of the semicircular canals and innervation of sensory epithelia. Specific tissues and cell types appear uniquely sensitive to Chd7 dosage, but the cellular Chd7 expression patterns and mechanisms of Chd7 deficiency in cell proliferation, differentiation, and survival are not known. Moreover, CHD7 interacting partners and downstream targets in the ear and neural cells are not characterized. Such knowledge would help guide rational development of therapies for inner ear defects. Our global hypothesis is that CHD7 functions in a transcriptional complex to repress or activate downstream target genes in developing ear and neural tissues. We have three specific aims: (1) Characterize cell proliferation, survival, and differentiation in Chd7 mutant mice, (2) Determine the contributions of CHD7-expressing tissues to inner ear development, and (3) Characterize cultured inner ear and neural stem cells from wildtype and Chd7 mutant embryos, and use them to determine whether CHD7 directly binds the promoters of candidate target genes. Results of proposed experiments will bring novel insights into fundamental processes of chromatin remodeling and transcriptional regulation. Improved understanding of tissue-specific requirements for Chd7 might also improve the diagnosis and treatment of CHARGE-related inner ear and other developmental defects.