Developmental Mechanisms of the Chromodomain Gene Chd7

描述(由申请人提供)：听力、视觉、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因素。近三分之一的人口在一生中患有味觉、嗅觉、听力或平衡方面的感觉障碍。目前先天性或先天性心脏病的治疗方法 获得性感觉障碍是严格支持的，再生疗法的开发存在严重的未得到满足的需求。充电综合征是一种多感官障碍，仅次于亚瑟综合征，是导致聋盲的第二大原因。Charge的特征是眼部缺陷、心脏缺陷、后鼻孔闭锁、生长发育迟缓(包括智力障碍和自闭症)、生殖器发育不良(包括性腺激素减退)，以及耳朵缺陷，包括耳聋和内耳发育不良。电荷是由编码DNA结合的ATP依赖的染色质重塑蛋白的CHD7基因的杂合突变引起的。CHD7功能的研究与多种感觉障碍相关，因为它在发育过程中以及在成熟的耳、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有的方式，在整个基因组的增强子序列和转录起始点与甲基化的组蛋白结合。目前面临的挑战包括识别介导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缺乏症的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是嗅觉上皮、内耳和前脑室下区神经干细胞增殖的主要正向调节因子。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缺乏之间的表型存在显著重叠，这增加了控制维生素A水平可能会影响CHD7效应的可能性。初步数据表明，改变的维甲酸信号部分挽救了CHD7杂合子缺失表型，提示CHD7和维甲酸通过共同的信号通路发挥作用。我们提出了一个全球假设，即CHD7和维甲酸信号转导信号共享共同的机制或遗传靶点，这些机制或遗传靶点对于颅面结构的正常发育和神经干细胞的增殖是必要的。我们提出四个目标来验证这一假设：(1)确定在CHD7缺陷小鼠中观察到的视黄酸信号上调是否是表型的重要组成部分，(2)评估视黄酸信号在小鼠神经前体细胞增殖中对CHD7的依赖，(3)确定神经干细胞中常见的维甲酸信号和CHD7结合部位，以及(4)测试最近从CHD7突变正电荷个体中产生的人类诱导的多能干细胞，以促进视黄酸依赖的增殖和分化。这些结果将确定染色质介导的基因在哺乳动物细胞中表达的基本机制，并有助于为临床前试验的基本设计奠定基础。

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.