Role of Chd7 in neural development and maintenance

描述（由申请人提供）：正常组织的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）蛋白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单倍体功能不全导致CHARGE综合征，这是一种以眼结肠瘤、心脏缺陷、先天性闭锁、生长发育迟缓、生殖器发育不全和耳聋、前庭功能障碍等耳部异常为特征的多重异常病症。许多CHARGE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突变可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，我们培养了携带来自CHD7缺陷基因捕获的lacZ报告基因胚胎干细胞的Chd7Gt等位基因的小鼠，以及最近培养的携带条件CHD7缺失等位基因Chd7flox的小鼠。Chd7缺失小鼠是E11致胚胎死亡的。Chd7Gt/+小鼠表现出与人类CHARGE表型相似的特征，包括出生后生长迟缓、前庭功能障碍和嗅觉缺陷，包括嗅球发育不全和低嗅觉。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感觉神经元的减少。然而，脑室下区神经干细胞增殖缺陷也可能导致人类和小鼠Chd7缺乏症中常见的嗅球缺陷。GnRH神经元沿嗅觉感觉神经元从鼻子到嗅球并最终到下丘脑的迁移缺陷在Kallmann综合征中很常见，并且也可能导致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在神经发育中的功能作用。本研究的长期目标是确定CHD7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。普遍的假设是，CHD7调节神经干细胞的增殖和神经发生在嗅觉和内分泌组织的发育和维持中。有三个具体目的：1)验证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是成年小鼠正常下丘脑-垂体信号传导所必需的假设。3)验证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产生不同的影响。

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.