Epigenetics of inner ear neurosensory cell development

摘要 基因表达的表观遗传调控是通过DNA和相关的组蛋白的可遗传变化来实现的。 这种修饰，包括甲基化、乙酰化和核小体重新定位，具有主要的和 对发育和疾病的作用知之甚少。最近的研究已经开始探索表观遗传学 听力和平衡障碍对生活质量造成负面影响，并对社会经济造成重大影响 数百万美国人的负担。在患有听力或平衡障碍的儿童和成人中， 耳蜗上皮、前庭上皮及相关神经元常被破坏。在内耳期间 在发育过程中，来自耳囊的神经感觉前体细胞产生感觉毛细胞和 前庭耳蜗神经元。经常扰乱听力发育的基因突变和表观遗传学变化 导致毛细胞和神经元形成不当，导致听力损失。铬结构域解旋酶DNA 结合蛋白7(CHD7)是一种依赖于ATP的表观遗传性染色质重构体，与内耳有关 发展。CHD7基因突变导致Charge综合征(眼缺损、心脏缺陷、先天性闭锁 后鼻孔，生长发育迟缓，生殖器发育不全和青春期延迟，以及耳朵 异常)。CHD7缺失的患者通常被诊断为混合传导和感觉神经性听力。 然而，导致感音神经性听力损失的致病机制尚不清楚。在内心深处 CHD7在神经感觉前体细胞、间充质细胞、感觉上皮细胞等中动态表达。 耳聋细胞类型。然而，目前还不清楚是哪种耳廓细胞类型(S)和什么类型的顺式调节元件(S) 对致病的CHD7突变的存在感到不安。此外，CHD7已被证明可以重新定位 核小体在体外，而CHD7在体内的耳部发育过程中的染色质重塑活性尚未 已经确定了。CHD7在不同顺式调控元件上的丰富程度与细胞类型有关，而我们的 初步研究发现CHD7与以前的长非编码RNA转录本的启动子结合 永生化多能耳祖细胞(IMOPs)的神经元分化。我们假设CHD7形成 耳神经感觉前体细胞染色质重塑复合体与顺式调节元件结合 调节转录。我们将使用小鼠遗传学、单细胞遗传学的组合来检验我们的假设 测序方法和超分辨率显微镜。这些研究的结果将有助于确定 感音神经性耳聋的潜在机制，加强对内源性表观遗传调控的理解 耳朵神经感觉细胞发育，并贡献知识帮助设计再生或修复 内耳的治疗方法。

ABSTRACT Epigenetic regulation of gene expression occurs via heritable changes in DNA and associated histone proteins. Such modifications, which include methylation, acetylation, and nucleosome repositioning, have a major and poorly understood role in development and disease. Recent studies have begun to explore epigenetics of hearing and balance disorders which negatively impact quality of life and impose a significant socioeconomic burden on millions of Americans. In both children and adults with hearing or balance disorders, development of the cochlear epithelium, vestibular epithelia and associated neurons are often disrupted. During inner ear development, neurosensory progenitors from the otic vesicle give rise to sensory hair cells and vestibulocochlear neurons. Mutations and epigenetic changes in genes that perturb otic development often cause improper hair cell and neuron formation, resulting in hearing loss. The chromodomain helicase DNA binding protein 7 (CHD7) is an ATP dependent epigenetic chromatin remodeler implicated in inner ear development. Mutations in CHD7 cause CHARGE syndrome (ocular Coloboma, Heart defects, Atresia of the choanae, Retardation of growth and development, Genital hypoplasia and pubertal delay, and Ear abnormalities). Patients with CHD7 loss are often diagnosed with mixed conductive and sensorineural hearing loss; however, the pathogenic mechanisms that cause sensorineural hearing loss are not known. In the inner ear, CHD7 is dynamically expressed in neurosensory progenitors, mesenchyme, sensory epithelium, and other otic cell types. However, it is unclear which otic cell type(s) and what type of cis-regulatory element(s) are perturbed in the presence of pathogenic CHD7 mutations. In addition, CHD7 has been shown to reposition nucleosomes in vitro, yet the chromatin remodeling activity of CHD7 in vivo during otic development has not been determined. Enrichment of CHD7 at different cis-regulatory elements is cell type dependent, and our preliminary studies have identified CHD7 binding to the promoter of long noncoding RNA transcripts preceding neuronal differentiation in immortalized multipotent otic progenitors (iMOPs). We hypothesize that CHD7 forms a chromatin remodeling complex in otic neurosensory progenitors and binds to cis-regulatory elements to regulate transcription. We will test our hypothesis using a combination of mouse genetics, single-cell sequencing approaches, and super-resolution microscopy. Results from these studies will help identify mechanisms underlying sensorineural hearing loss, enhance understanding of epigenetic regulation of inner ear neurosensory cell development, and contribute knowledge to help design regenerative or restorative therapies for the inner ear.