Developmental Mechanisms of the Chromodomain Gene Chd7

描述（由申请人提供）：听力、视力、嗅觉和疼痛感知的综合障碍是全球神经认知障碍和适应功能的主要原因。近三分之一的人口在其一生中患有涉及味觉、嗅觉、听觉或平衡的感觉障碍。目前治疗先天性或 获得性感觉障碍是严格支持性的，并且对于再生疗法的开发存在关键的未满足的需求。CHARGE综合征是一种多重感觉障碍，仅次于Usher综合征，是导致聋盲的原因。CHARGE的特征为眼部缺损、心脏缺陷、软骨闭锁、生长发育迟缓（包括智力残疾和自闭症）、生殖器发育不全（包括低促性腺激素性性腺功能减退症）和耳部缺陷（包括耳聋和内耳发育不良）。CHARGE由编码DNA结合ATP依赖性染色质重塑蛋白的CHD7基因中的杂合突变引起。CHD7功能的研究与多种感觉障碍相关，因为它在发育期间以及在成熟的耳、眼、鼻、颅面、脑和颅面组织中高度表达。CHD7以组织和发育阶段特异性的方式在整个基因组的增强子序列和转录起始位点与甲基化组蛋白结合。目前的挑战包括鉴定介导CHD7细胞效应的重要靶基因和信号通路，以及确定哺乳动物CHD7缺陷表型是否可以预防或逆转。我们的实验室研究了CHARGE综合征的小鼠模型，发现CHD7是嗅上皮、内耳和前脑脑室下区神经干细胞增殖的主要正调节因子。有趣的是，在人类和小鼠中，CHARGE综合征、维甲酸胚胎病和维生素A缺乏症之间的表型存在显著重叠，这提高了控制维生素A水平可能影响CHD7效应的可能性。初步数据表明，改变视黄酸信号部分拯救了CHD7杂合子无效表型，表明CHD7和视黄酸通过共同的信号通路发挥功能。我们已经开发了一个全球性的假设，即CHD7和视黄酸信号传导具有共同的机制或遗传靶点，这是颅面结构和神经干细胞增殖正常发育所必需的。我们提出了四个目标来检验这一假设：（1）确定视黄酸信号传导的上调是否是在Chd7缺陷小鼠中观察到的表型的必要组成部分，（2）评价视黄酸信号传导在小鼠神经祖细胞增殖中的CHD7依赖性，（3）鉴定神经干细胞中常见的视黄酸信号传导和CHD7结合位点，和（4）测试最近从CHD7突变阳性CHARGE个体产生的人诱导多能干细胞的视黄酸依赖性增殖和分化。结果将确定染色质介导的基因表达在哺乳动物细胞中的基本机制，并帮助建立一个基础的合理设计的临床前试验。

DESCRIPTION (provided by applicant): Combined impairments in hearing, vision, olfaction, and pain perception are a major contributor to neurocognitive disabilities and adaptive functioning worldwide. Nearly one-third of the population suffers from sensory disorders involving taste, smell, hearing, or balance in their lifetime. Current treatments for congenital or acquired sensory impairments are strictly supportive, and there is a critical unmet need for the development of regenerative therapies. CHARGE Syndrome is a multiple sensory disorder second only to Usher Syndrome as a cause of deaf blindness. CHARGE is characterized by ocular coloboma, heart defects, atresia of the choanae, retardation of growth and development (including intellectual disability and autism), genital hypoplasia (including hypogonadotropic hypogonadism), and ear defects including deafness and inner ear dysplasia. CHARGE is caused by heterozygous mutations in the CHD7 gene encoding a DNA binding ATP- dependent chromatin remodeling protein. Study of CHD7 function is relevant for multiple sensory disorders, as it is highly expressed during development and in mature ear, eye, nasal, craniofacial, brain, and craniofacial tissues. CHD7 binds to methylated histones at enhancer sequences and transcription start sites throughout the genome, in a tissue and developmental stage-specific manner. Current challenges include identification of important target genes and signaling pathways that mediate the cellular effects of CHD7, and determination of whether mammalian CHD7 deficiency phenotypes can be prevented or reversed. Our laboratory has studied mouse models of CHARGE Syndrome and found that CHD7 is a major positive regulator of neural stem cell proliferation in the olfactory epithelium, inner ear, and forebrain subventricular zone. Interestingly, there is significant overlap in phenotypes between CHARGE Syndrome, retinoic acid embryopathy, and vitamin A deficiency in both humans and mice, raising the possibility that control of vitamin A levels may influence CHD7 effects. Preliminary data indicate that altered retinoic acid signaling partially rescues Chd7 heterozygous null phenotypes, suggesting CHD7 and retinoic acid function through common signaling pathways. We have developed the global hypothesis that CHD7 and retinoic acid signaling share common mechanisms or genetic targets that are necessary for proper development of craniofacial structures and neural stem cell proliferation. We propose four aims to test this hypothesis: (1) Determine whether up-regulation of retinoic acid signaling is an essential component of the phenotypes observed in Chd7 deficient mice, (2) Evaluate CHD7- dependence of retinoic acid signaling in proliferation of mouse neural progenitors, (3) Identify common retinoic acid signaling and CHD7 binding sites in neural stem cells, and (4) Test recently generated human induced pluripotent stem cells from CHD7-mutation positive CHARGE individuals for retinoic acid dependent proliferation and differentiation. Results will identify basic mechanisms of chromatin-mediated gene expression in mammalian cells and help establish a basis for the rationale design of pre-clinical trials.