Regulation of inner ear development by FGF signals and effectors

内耳上皮的形态发生需要几个信号通路的协调部署和 精神障碍会导致听力和/或平衡的异常。随着人工耳蜗术的到来而治疗 听力损失即使在内耳畸形的情况下，准确地了解这种畸形是如何发生的也是至关重要的。 影响听觉神经节和神经。此外，鉴于人们对内耳体外培养的高度关注 用于移植的细胞类型和体内操纵发育信号分子以促进 不同类型内耳细胞在听力恢复中的分化及其作用和调控 调控耳部分化和形态发生的信号及其效应器对于推进治疗是必要的。 表达了编码FGF3和FGF10的基因，这些基因是通过FGFR2b和FGFR1b发出信号的配体 在上皮域和神经节域的耳廓发育过程中都有动态变化。进行的研究 常规Fgf3和Fgf10条件性基因敲除小鼠以及表达A基因的小鼠的Mansour实验室 强力霉素诱导的配体陷阱(DnFGFR2b)快速抑制FGFR1b和FGFR1b的信号传导 FGFR2b，表明Fgf3和Fgf10在耳囊形成的胎盘谱系中不是必需的，但 随后需要用于耳囊构型、神经母细胞维持、上皮细胞增殖以及两者 前庭和耳蜗的形态发生。此外，首次全基因组分析耳囊mrna揭示了 FGFR2b/1b信号靶点，定义了涉及耳廓形态发生和功能的基因的新候选基因。 这项提议有两个目的，以解决以下假设：1)FGFR2b/1b信号需要持续 对于耳神经母细胞的指定和维持，以及在后期阶段，间充质信号也是如此 与上皮域和神经节域一样，是耳蜗上皮细胞分化和神经节形成所必需的 2)FGFR2b/1b下游靶基因介导FGFR2b/1b的部分或全部作用 听觉形态发生和神经节形成的信号转导。探讨FGFR2b/1b信号在耳聋早期的作用 神经节形成及其在上皮分化和神经节维持中的作用 将利用dnFGFR2b的普遍存在和Cre限制性表达，以及形态和分子标记 将评估这两个组织中耳廓图案、增殖和存活的情况。确定……的角色 FGFR2b/1b信号的下游靶点，两个编码转录因子的基因被激活 FGFR2b/1b信号和一个编码BMP信号调节因子的基因被FGFR2b/1b抑制 将对信令进行研究。将为每个基因产生特殊的条件突变，并且它们的形态和 将对功能开发进行评估。此外，BMP监管机构在多大程度上有助于 将评估dnFGFR2b的表型和过度表达BMP调节器的影响。 结果将提供新的知识，将促进未来的努力操纵成纤维细胞生长因子信号 听力恢复系统。

Morphogenesis of the inner ear epithelium requires coordinated deployment of several signaling pathways and disruptions cause abnormalities of hearing and/or balance. With the advent of cochlear implantation to treat hearing loss even in cases of inner ear malformation, it is critical to understand exactly how such malformations affect the auditory ganglia and innervation. Also, in light of the intense focus on in vitro generation of inner ear cell types for transplantation and in vivo manipulation of developmental signaling molecules to promote differentiation of various inner ear cells for hearing restoration, elucidating the roles and regulation of such signals and their effectors governing otic differentiation and morphogenesis are necessary to advance treatment. The genes encoding FGF3 and FGF10, ligands that signal through FGFR2b and FGFR1b, are expressed dynamically throughout otic development in both epithelial and ganglion domains. Studies conducted by the Mansour Lab of both conventional Fgf3 and Fgf10 conditional knockout mice and those expressing a doxycycline-inducible ligand trap (dnFGFR2b) that rapidly inhibits signaling through both FGFR1b and FGFR2b, showed that Fgf3 and Fgf10 are not required in the placode lineage for otocyst formation, but are required subsequently for otocyst patterning, neuroblast maintenance, epithelial proliferation and both vestibular and cochlear morphogenesis. Furthermore, the first genome wide analyses of otocyst mRNA revealed FGFR2b/1b signaling targets that define novel candidates for genes involved in otic morphogenesis and function. This proposal has two Aims addressing the hypotheses that 1) FGFR2b/1b signaling is required continuously for both otic neuroblast specification and maintenance, and that at later stages, mesenchymal signaling, as well as that in the epithelial and ganglion domains, is required for cochlear epithelial differentiation and ganglion maintenance and 2) FGFR2b/1b downstream target genes mediate some or all of the effects of FGFR2b/1b signaling on otic morphogenesis and gangliogenesis. To determine the early role of FGFR2b/1b signaling in otic ganglion formation and its later role in epithelial differentiation and ganglion maintenance, DOX-induced ubiquitous and CRE-limited expression of dnFGFR2b will be employed and morphology and molecular markers of otic patterning, proliferation and survival in both tissues will be assessed. To determine the roles of downstream targets of FGFR2b/1b signaling, two genes encoding transcription factors that are activated by FGFR2b/1b signaling and one gene encoding a BMP signaling regulator that is repressed by FGFR2b/1b signaling will be studied. Otic conditional mutants will be generated for each gene, and their morphologic and functional development will be assessed. In addition, the extent to which the BMP regulator contributes to the dnFGFR2b phenotypes and the effects of overexpressing the BMP regulator will be assessed. The results will contribute new knowledge that will facilitate future efforts to manipulate the FGF signaling system for hearing restoration.