Genomic architecture of Shh dependent cochlear morphogenesis

小鼠耳蜗起源于耳泡的腹侧延伸。在几 在胚胎发育过程中，这种生长物经历了一个复杂的形态发生序列。 导致其延长、卷曲和分化为感觉和非感觉细胞类型的变化 这对听力至关重要（格罗夫斯和Fekete，2012）。先天性耳蜗畸形通常会导致 耳聋，强调彻底了解其发展的重要性（Jackler等人，1987年）。 我们以前描述了一个关键功能的刺猬（嘘）信号通路，促进 耳泡内的腹侧特性，这是耳蜗管随后生长所必需的 （Riccomagno等人，2002; Bok等人，2007 b; Brown and Epstein，2011）。缺乏Shh的小鼠胚胎，或 携带Smoothened（Smoecko）的耳部条件性敲除，Smoothened是Shh信号转导的基本途径。 组成部分，表现出耳蜗发育不全。我们还分类了几种在转录调控中起关键作用的转录因子。 耳蜗发育作为Shh的转录靶点（Pax 2，Otx 2，Gata 3）或效应子（Gli 2，Gli 3） 腹侧耳上皮内的信号传导。然而，尽管有这些进步， Shh依赖性转录因子促进耳蜗管生长的机制尚不清楚， 这主要是因为在该转录级联中作用于下游的基因尚未确定。 为了鉴定Shh信号传导的新靶点，我们比较了对照组的全基因组表达谱。 和Smoecko内耳在E11.5，当耳蜗原基是明显的，并揭示了一个有趣的嘘 在耳蜗中具有已知和以前未表征作用的反应基因 形态发生有趣的是，这些基因中有几个在发育的后期仍保持其表达 在耳蜗管的前感觉域，提高了Shh信号启动耳蜗的可能性。 假定的感觉上皮，用于其发育的后续步骤。我们建议将 腹侧耳基因组根据以下实验计划： 表达和对Shh信号传导的依赖性（Aim 1）;解码它们的顺式调节结构（Aim 2）;以及 评估其对耳蜗发育的功能贡献（目标3）。这些实验的结果应该 推进我们对耳蜗的分子和细胞机制的基本理解 内耳内的形态发生和细胞命运特化。

The mouse cochlea derives from the ventral extension of the otic vesicle. Over the course of several days during embryonic development, this outgrowth undergoes a complex sequence of morphogenetic changes resulting in its lengthening, coiling and differential patterning into sensory and nonsensory cell types that are essential for hearing (Groves and Fekete, 2012). Congenital malformations of the cochlea often lead to deafness, emphasizing the importance of a thorough understanding of its development (Jackler et al., 1987). We previously described a critical function of the Sonic hedgehog (Shh) signaling pathway in promoting ventral identity within the otic vesicle that is necessary for the subsequent outgrowth of the cochlear duct (Riccomagno et al., 2002; Bok et al., 2007b; Brown and Epstein, 2011). Mouse embryos lacking Shh, or carrying an ear conditional knockout of Smoothened (Smoecko), an essential Shh signal transduction component, exhibit cochlear agenesis. We also classified several transcription factors with key roles in cochlear development as either transcriptional targets (Pax2, Otx2, Gata3) or effectors (Gli2, Gli3) of Shh signaling within the ventral otic epithelium. However, despite these advances, a detailed understanding of the mechanism by which Shh dependent transcription factors promote cochlear duct outgrowth remains unclear, primarily since the genes acting downstream in this transcriptional cascade have yet to be determined. To identify novel targets of Shh signaling we compared the genome-wide expression profiles of control and Smoecko inner ears at E11.5, when the cochlea anlage is evident, and uncovered an intriguing set of Shh responsive genes with a combination of known and previously uncharacterized roles in cochlear morphogenesis. Interestingly, several of these genes maintain their expression at later stages of development within the prosensory domain of the cochlear duct, raising the possibility that Shh signaling is priming the presumptive sensory epithelium for subsequent steps in its development. We propose to characterize the ventral otic gene set according to the following experimental plan: classify their spatiotemporal patterns of expression and dependency on Shh signaling (Aim 1); decode their cis-regulatory architecture (Aim 2); and assess their functional contribution to cochlear development (Aim 3). The results of these experiments should advance our fundamental understanding of the molecular and cellular mechanisms underlying cochlear morphogenesis and cell fate specification within the inner ear.