Role of Chd7 in neural development and maintenance

描述(申请人提供)：正常的组织发育和维持需要精确的时间和正确的基因表达定位。一些证据表明，染色质结构域(CHD)家族是染色质重塑和基因表达的关键调节因子。在人类中，CHD7的单倍体不足会导致Charge综合征，这是一种多重异常情况，特征是眼部缺损、心脏缺陷、后鼻孔闭锁、生长发育迟缓、生殖器发育不良以及包括耳聋和前庭疾病在内的耳朵异常。许多有过敏症的患者表现出卡尔曼样特征，包括嗅觉和内分泌功能障碍。临床证据表明，CHD7基因突变会导致多效性发育缺陷；然而，这些缺陷背后的机制尚未确定。为了研究CHD7在发育中的作用，我们产生了携带CHD7缺陷基因的Chd7Gt等位基因的小鼠，该等位基因来自捕获LacZ报告胚胎干细胞的CHD7报告基因，以及最近产生的条件CHD7零等位基因Chd7flx的小鼠。CHD7基因缺失的小鼠在E11之前是胚胎致死的。Chd7Gt/+小鼠表现出与人类相似的电荷表型特征，包括出生后生长迟缓、前庭功能障碍和嗅觉缺陷，包括嗅球发育不良和嗅觉减退。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缺陷和嗅觉上皮中嗅觉神经元减少所致。然而，脑室下区神经干细胞增殖缺陷也可能导致嗅球缺陷，这在CHD7缺陷的人和小鼠中都很常见。在Kallmann综合征中，GnRH神经元沿着嗅觉神经元从鼻子到嗅球并最终到达下丘脑的缺陷是常见的，也可能导致CHD7突变小鼠的内分泌缺陷。对CHD7突变小鼠的Kallmann样特征的进一步分析可能表明CHD7在神经发育中发挥功能作用。这项研究的长期目标是确定CHD7在神经组织中的作用，以帮助改进嗅觉和内分泌缺陷的诊断和治疗。全球假说是CHD7在嗅觉和内分泌组织的发育和维持中调节神经干细胞的增殖和神经发生。有三个具体的目标：1)检验CHD7是维持成人脑室下区神经干细胞所必需的假设。2)验证CHD7是正常成年小鼠下丘脑-垂体信号传导所必需的假设。3)检验CHD7剂量(即单倍体充足与纯合子缺失)对中枢神经系统神经干细胞造成不同的影响。 公共卫生相关性：这项研究的结果将使我们对CHD7如何有助于嗅觉和内分泌组织的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机制可能对嗅觉和内分泌组织的建立和/或维持至关重要。这些结果还可能有助于公共卫生改进气味检测和生殖功能障碍及相关疾病的治疗方法。

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.