Developmental Mechanisms of the Chromodomain Gene Chd7

这些研究对于提高我们对发育缺陷的认识具有直接的意义。 与CHD7缺乏症相关。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。以DNA结合和ATP依赖为特征的色域蛋白 解旋酶结构域在染色质重塑中的作用知之甚少，并对表观遗传产生影响 对基因表达的影响。在人类中，CHD7单倍体不足，CHD7是CHD7第三亚家族的成员 染色域蛋白，导致电荷综合症。充电是一种多发性异常障碍 以眼部缺陷、心脏缺陷、后鼻孔闭锁、生长迟缓和 发育、生殖器发育不全和耳朵畸形，包括耳聋和前庭功能障碍。我们 产生了捕获零等位基因(Chd7Gt/+)的杂合子小鼠。这些老鼠表现出许多特征 与人类相似的充电表型，包括严重的内耳缺陷和出生后发育迟缓。 ChD7Gt/+小鼠也在CHD7阳性组织中表达-半乳糖苷酶报告基因，并可用于 追踪CHD7缺陷细胞的命运。人类和小鼠的临床特征是 可变性和不完全穿透性，是两人最常见的发育畸形 CHD7功能丧失的小鼠为半规管发育不全或发育不良。内耳缺陷伴发 小鼠的CHD7缺陷是复杂的，包括半规管畸形和神经支配 感觉上皮细胞。特定的组织和细胞类型似乎对CHD7的剂量特别敏感，但 CHD7在细胞增殖、分化、分化过程中的表达模式及其机制 以及生存情况尚不得而知。此外，CHD7的互动伙伴和下游目标在耳朵和 神经细胞没有被定性。这样的知识将有助于指导合理开发治疗方法 内耳缺陷。我们的全球假设是CHD7在转录复合体中发挥作用，以抑制或 激活发育中的耳朵和神经组织中的下游靶基因。我们有三个具体目标： (1)研究CHD7突变小鼠的细胞增殖、存活和分化情况， (2)确定CHD7表达组织对内耳发育的贡献； (3)从野生型和CHD7突变胚胎中鉴定培养的内耳和神经干细胞，并使用 以确定CHD7是否直接与候选靶基因的启动子结合。 拟议的实验结果将为染色质的基本过程带来新的见解 重塑和转录调控。提高对组织特定要求的理解 CHD7也可能改善电荷相关内耳和其他疾病的诊断和治疗 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.