Factors Regulating Inner Ear Specification

脊椎动物的内耳是一种感觉器官，涉及听觉、平衡和加速度检测。它 从称为耳基板的胚胎外胚层增厚发展而来。定义分子 导致耳基板特化的过程对于理解内耳发育是必不可少的。 Sox蛋白包括一大类转录调节因子。这个家族的一个成员，Sox 9，一个很好的- 已建立的软骨形成和性别决定的调节因子，也是最早表达的基因之一， 假定的耳基板。Sox 9突变导致了一种致命的人类疾病--肢端发育不良（CD） 以严重的骨骼畸形和XY性反转为特征。罕见CD患者报告， 存活的人表明他们也受到感觉神经性耳聋的影响，这表明Sox 9可能在神经性耳聋中起作用。 在听觉系统发育中的重要作用。 我们已经表明，在非洲爪蟾中Sox 9的耳表达是在耳的感觉层的早期开始的。 外胚层在该组织中，Sox 9表达受Fgf和Wnt信号传导调节，并与Pax 8共定位， 是最早响应耳基板诱导信号而表达的基因之一。Sox 9蛋白的缺失 使用吗啉代反义寡核苷酸的整个胚胎引起早期和晚期耳毒性的急剧丧失， 标记，在最极端的情况下，这些胚胎无法形成形态上可识别的耳 囊泡下面的实验将验证以下假设：转录因子Sox 9是一个关键的 内耳规格所需的调节途径的组成部分。 我们提出：1-通过建立Sox 9在耳基板中表达的分子调控因子， 激活耳基板中Sox 9表达的信号的来源;以及 Fgf和Wnt信号传导对于整个胚胎和动物外植体中耳基板特化的充分性。 2-表征Xenpopus Sox 9缺陷胚胎的耳表型3-鉴定Sox 9相互作用 使用酵母双杂交筛选耳基板中的伴侣分子，因为已知Sox蛋白 通过与细胞类型特异性伴侣分子的相互作用来调节其靶基因。 这类伴侣分子的研究将进一步加深我们对Sox 9介导的基因调控的理解， 发育中的内耳

The vertebrate inner ear is a sensory organ implicated in hearing, balance and detection of acceleration. It develops from a thickening of the embryonic ectoderm known as the otic placode. Defining the molecular processes leading to specification of the otic placode is essential to understand inner ear development. Sox proteins comprise a large class of transcriptional regulators. One member of this family, Sox9, a well- established regulator of chondrogenesis and sex determination, is also one of the earliest genes expressed in the presumptive otic placode. Mutations in Sox9 result in campomelic dysplasia (CD), a fatal human disorder characterized by severe skeletal malformations and XY sex reversal. Reports of rare CD patients that survived indicate that they are also affected with sensorineural deafness, suggesting that Sox9 may play an important role in the development of the auditory system. We have shown that the otic expression of Sox9 in Xenopus is initiated early in the sensory layer of the ectoderm. In this tissue, Sox9 expression is regulated by Fgf and Wnt signaling and co-localizes with Pax8, one of the earliest gene expressed in response to otic placode inducing signals. Depletion of Sox9 protein in whole embryos using morpholino antisense oligonucleotides causes a dramatic loss of early and late otic markers, and in the most extreme cases these embryos fail to form a morphologically recognizable otic vesicle. The experiments below will test the following hypothesis: the transcription factor Sox9 is a key component of regulatory pathway required for inner ear specification. We propose: 1-To define the molecular regulators of Sox9 expression in the otic placode by establishing the origin of the signals activating Sox9 expression in the otic placode; and defining the requirement and sufficiency of Fgf and Wnt signaling for otic placode specification in whole embryos and animal explants. 2-To characterize the ear phenotype of Xenpopus Sox9-deficient embryos 3-To identify Sox9-interacting partner molecules in the otic placode using a yeast two-hybrid screen, since Sox proteins are known to regulate their target genes through interaction with cell type-specific partner molecules.The characterization of such partner molecules should further our understanding of Sox9-mediated gene regulation in the context of the developing inner ear.