Role of Chd7 in neural development and maintenance

描述（由申请人提供）：正常组织发育和维持需要精确的时间和基因表达的正确定位。一些证据表明，染色质结构域（CHD）蛋白质家族是染色质重塑和基因表达的关键调节因子。在人类中，CHD 7的单倍不足引起CHARGE综合征，一种以眼缺损、心脏缺陷、软骨闭锁、生长发育迟缓、生殖器发育不全和耳异常（包括耳聋和前庭障碍）为特征的多重异常病症。许多CHARGE患者表现出Kallmann样特征，包括嗅觉和内分泌功能障碍。临床证据表明，CHD 7突变导致多效性发育缺陷;然而，这些缺陷的机制尚未确定。为了研究CHD 7在发育中的作用，我们产生了携带来自Chd 7缺陷基因捕获的lacZ报告胚胎干细胞的Chd 7 Gt等位基因的小鼠，并且最近产生了具有条件性Chd 7无效等位基因Chd 7 flox的小鼠。Chd 7基因敲除小鼠在E11时具有胚胎致死性。Chd 7 Gt/+小鼠表现出与人CHARGE表型相似的特征，包括出生后生长延迟、前庭功能障碍和嗅觉缺陷，包括嗅球发育不全和嗅觉减退。这些数据表明，嗅觉功能障碍可能主要是由于神经干细胞增殖的缺陷和嗅觉感觉神经元在嗅上皮减少。然而，脑室下区神经干细胞增殖的缺陷也可能导致人类和Chd 7缺乏小鼠中常见的嗅球缺陷。GnRH神经元迁移缺陷沿着嗅觉感觉神经元从鼻子到嗅球并最终到下丘脑在卡尔曼综合征中很常见，并且也可能导致Chd 7突变小鼠的内分泌缺陷。进一步分析Chd 7突变小鼠的Kallmann样特征可能表明CHD 7在神经发育中的功能作用。这项研究的长期目标是确定CHD 7在神经组织中的作用，以帮助改善嗅觉和内分泌缺陷的诊断和治疗。总体假设是CHD 7调节嗅觉和内分泌组织发育和维持中的神经干细胞增殖和神经发生。有三个具体的目的：1）测试的假设，Chd 7是需要在成人脑室下区的神经干细胞的维持。2)测试Chd 7是成年小鼠正常下丘脑-垂体信号传导所必需的假设。3)测试假设，Chd 7剂量（即。单倍体充足与纯合子丢失）对中枢神经系统神经干细胞产生不同的影响。 公共卫生相关性：这项研究的结果将导致我们对CHD 7如何促进嗅觉和内分泌组织发育和维持的基本理解取得重大进展。染色质重塑和转录调控的基础机制可能是建立和/或维持嗅觉和内分泌组织的关键。这些结果也可能有助于改善气味检测和生殖功能障碍及相关疾病的治疗方法的发展。

DESCRIPTION (provided by applicant): Normal tissue development and maintenance requires precise timing and correct localization of gene expression. Several lines of evidence indicate that the chromodomain (CHD) families of proteins are critical regulators of chromatin remodeling and gene expression. In humans, haploinsufficiency for CHD7 causes CHARGE syndrome, a multiple anomaly condition characterized by ocular coloboma, heart defects, atresia of the choanae, retarded growth and development, genital hypoplasia and ear abnormalities including deafness and vestibular disorders. Many patients with CHARGE display Kallmann-like features which include olfactory and endocrine dysfunction. Clinical evidence indicates that mutations in CHD7 lead to pleiotropic developmental defects; however, the mechanisms underlying these defects have not yet been determined. In order to study the role of CHD7 in development, we generated mice carrying a Chd7Gt allele derived from Chd7 deficient gene trapped lacZ reporter embryonic stem cells and recently generated mice with a conditional Chd7 null allele, Chd7flox. Chd7 null mice are embryonic lethal by E11. Chd7Gt/+ mice exhibit features similar to human CHARGE phenotypes, including postnatal growth delay, vestibular dysfunction, and olfactory defects which include olfactory bulb hypoplasia and hyposmia. These data indicate that olfactory dysfunction may primarily result from defects in neural stem cell proliferation and reduced olfactory sensory neurons in the olfactory epithelium. However, defects in neural stem cell proliferation in the sub ventricular zone may also contribute to olfactory bulb defects common in both humans and mice with Chd7 deficiency. Defects in GnRH neuronal migration along olfactory sensory neurons from the nose to the olfactory bulb and ultimately to the hypothalamus are common in Kallmann syndrome, and could also contribute to endocrine defects in Chd7 mutant mice. Further analysis of the Kallmann-like features in Chd7 mutant mice may indicate a functional role for CHD7 in neural development. The long term goal of this research is to determine the role of CHD7 in neural tissues in order to help improve diagnosis and treatment of olfactory and endocrine defects. The global hypothesis is that CHD7 regulates neural stem cell proliferation and neurogenesis in olfactory and endocrine tissue development and maintenance. There are three specific aims: 1) Test the hypothesis that Chd7 is required for maintenance of neural stem cells in the adult subventricular zone. 2) Test the hypothesis that Chd7 is necessary for normal hypothalamic-pituitary signaling in adult mice. 3) Test the hypothesis that Chd7 dosage (ie. Haploid sufficiency versus homozygous loss) causes differential effects on central nervous system neural stem cells. PUBLIC HEALTH RELEVANCE: The results of this research will lead to significant advances in our basic understanding of how CHD7 contributes to olfactory and endocrine tissue development and maintenance. The mechanisms that underlie chromatin remodeling and transcriptional regulation are likely to be critical for establishment and/or maintenance of olfactory and endocrine tissues. These results may also contribute to public health in the development of improved therapies for odorant detection and reproductive dysfunction and related disorders.