Cell Type Specific Transcriptional Cascades in Inner Ear Development

 描述(申请人提供)：遗传性非综合征性听力损失影响1：500的新生儿，年龄相关性听力损失困扰大多数老年人口。在大多数形式的听力损失中，毛细胞(HC)退化是常见的最终途径。我们研究的长期目标是破译内耳发育所必需的特定细胞类型的转录和信号级联反应，并应用这一知识来识别：(A)听力所必需的基因；(B)有效的分化调节因子，最终可用于恢复听力。Atoh1是HC-FATE的主要调节者，可能通过激活一系列转录因子(TF)和非调控基因发挥作用。然而，在耳聋的耳朵中强制表达Atoh1并不足以产生成熟的听性HC。因此，迫切需要确定介导新形成的HC分化的信号级联。在这个建议中，我们关注GFI1和RFX转录因子，它们在果蝇中的同源基因是Atoh1同源基因的直接靶标。我们最近发现了纤毛形成RFX蛋白在调节新生小鼠HC特异转录组中的进化保守作用，并确定Rfx3和Rfx7是HCS中含量最丰富的Rfx转录本。在特定的目标1中，我们将利用条件基因敲除小鼠来确定RFX在HC分化中的作用，并鉴定和验证RFX在HC中调控的靶基因。在特定的目标2中，我们将确定GFI1的分子靶点，GFI1是一个外部HC存活和前庭HC分化所必需的基因，并验证新发现的靶点在体内的作用。为了便于在公共领域传播在这一提案和其他提案中产生的数据，并作为建立内耳细胞类型特异性分化所需的转录网络的一步，我们将建立和维护Gear-一个听觉研究的基因表达门户网站。

 DESCRIPTION (provided by applicant): Hereditary non-syndromic hearing loss affects 1:500 newborns and age related hearing loss afflicts the majority of the elderly population. In most forms of hearing loss, hair cell (HC) degeneration is a common final pathway. The long-term goal of our research is to decipher the cell type-specific transcriptional and signaling cascades that are necessary for inner ear development, and to apply this knowledge to identify: (a) genes necessary for hearing; and (b) potent regulators of differentiation, which could ultimately be used to restore hearing. ATOH1 is a master regulator of HC-fate that likely functions through the activation of a series of transcription factors (TFs) as well as non-regulatory genes. However, forced expression of ATOH1 in deafened ears is not sufficient to generate mature auditory HCs. Therefore, there is a critical need to identify the signaling cascades mediating the differentiatio of newly formed HCs. In this proposal we focus on the GFI1 and RFX TFs, whose orthologs in Drosophila are immediate targets of the ATOH1 ortholog. We recently identified an evolutionarily conserved role for the ciliogenic RFX proteins in regulating the newborn mouse HC-specific transcriptome, and identified Rfx3 and Rfx7 as the most abundant Rfx transcripts in HCs. In Specific Aim 1 we will determine the role of RFX in HC differentiation using conditional knockout mice, and identify and validate the RFX-regulated target genes in HCs. In Specific Aim 2 we will identify the molecular targets of GFI1, a gene necessary for outer HC survival and vestibular HC differentiation, and validate the roles of newly identified targets in vivo. In orderto facilitate dissemination of data generated in this and other proposals in the public domain, and as a step towards building the transcriptional networks necessary for inner ear cell type-specific differentiation, we will build and maintain the gEAR - a gene Expression for Auditory Research portal.