Role of Fragile X Mental Retardation Protein on Gene Expression in Auditory Brainstem Development

脆性X综合征（FXS）是最常见的遗传性自闭症谱系障碍， 听觉特征，如对声音的超敏反应（听觉过敏）。FXS是由缺乏脆性X染色体引起的 精神发育迟滞蛋白（FMRP），已知其结合特定mRNA并抑制其翻译。小 关于FMRP如何影响中枢听觉通路的研究我们将研究FMRP对基因表达的影响， 使用完善的fmr 1基因敲除（KO）小鼠模型， 表现出听觉过敏和对噪音的反应。虽然， FMRP是一种翻译抑制蛋白，近年来在神经元中发现FMRP也能改变神经元中FMRP的表达水平， 许多mRNA。这是否发生在听觉脑干尚不清楚。我们有新的转录组数据 （未发表）显示，已知与FMRP结合并在FMRP中起作用的许多mRNA的水平， 突触通路，在fmr 1-KO耳蜗核中减少。这是如何发生的尚不清楚。目标1将 测试直接FMRP结合稳定结合mRNA的假设，但在FMRP不存在的情况下，这些 mRNA的稳定性降低（因此水平降低）。我们还将确定是否减少 mRNA的稳定导致蛋白质水平降低，或者如果它被FMRP介导的蛋白质水平的丧失所抵消， 翻译抑制，从而表现为增加的蛋白质水平。另一种可能性是FMRP作为 间接通过翻译抑制因子，如无义介导的mRNA衰变（NMD）因子， UPF1.来自我的研究导师实验室的未发表的数据表明，诱导多能干细胞 来自FXS患者的成纤维细胞表现出异常高水平的UPF 1（其mRNA被FMRP结合）， 导致过度活化的NMD，并因此降低细胞NMD靶mRNA的水平。基于 根据这些数据，目标2将检验NMD在fmr 1-KO耳蜗核中过度激活的假设， 基因下调。最后，它是已知的，FMRP参与活动依赖的过程。为 例如，FMRP的树突定位随着神经元能信号传导和传入活动的丧失而增加 可以减弱FMRP的翻译抑制。目的3验证FMRP对基因表达的影响 表达依赖于传入活动。我们将研究诱导性耳聋小鼠模型， 确定它是否可以表型复制fmr 1-KO，表明FMRP功能需要传入活动。的 PI具有丰富的分子生物学经验，并在一位受人尊敬的初级导师的指导下， RNA生物学家PI将掌握当前的RNA技术，并致力于成为一个独立的 调查员结果将揭示FMRP如何调节对听觉发育和可塑性重要的基因。 最终目的是揭示潜在的治疗靶点，以治疗听觉过敏和加工 紊乱导致听觉过敏的机制知之甚少，因为它不仅限于FXS， 并且影响高达15%的人口，该研究与一般人群相关。

Fragile X Syndrome (FXS) is the most common heritable autism spectrum disorder and is associated with auditory features such as hypersensitivity to sound (hyperacusis). FXS is caused by the absence of Fragile X mental retardation protein (FMRP), which is known to bind specific mRNAs and repress their translation. Little is known about how FMRP impacts the central auditory pathway. We will study FMRP effects on gene expression in the auditory brainstem, using the well-established fmr1-knockout (KO) mouse model, which exhibits auditory hypersensitivity and seizures in response to loud noise. Although the well-established role of FMRP is translational repression, it has been shown recently in neurons that FMRP can also change the level of many mRNAs. Whether this occurs in the auditory brainstem is unknown. We have novel transcriptome data (unpublished) showing that the levels of many mRNAs that are known to be bound by FMRP, and to function in synaptic pathways, are decreased in the fmr1-KO cochlear nucleus. How this occurs is not known. Aim 1 will test the hypothesis that direct FMRP binding stabilizes the bound mRNA, but in the absence of FMRP, these mRNAs have decreased stability (and, therefore, decreased level). We will also determine if decreased stabilization of mRNA leads to decreased protein level or if it is offset by the loss of FMRP-mediated translational repression so as to manifest as increased protein level. Another possibility is that FMRP acts indirectly through translational repression of factors, such nonsense-mediated mRNA decay (NMD) factor, UPF1. Unpublished data from my research mentor’s lab has shown that induced pluripotent stem cells derived from FXS-patient fibroblasts manifest an abnormally high level of UPF1 (whose mRNA is bound by FMRP), resulting in hyperactivated NMD and, as a consequence, reduced levels of cellular NMD target mRNAs. Based on these data, Aim 2 will test the hypothesis that NMD is hyperactivated in fmr1-KO cochlear nucleus, leading to gene downregulation. Lastly, it is known that FMRP is involved in activity dependent processes. For example, dendritic localization of FMRP is increased with glutamatergic signaling and loss of afferent activity can blunt translational repression by FMRP. Aim 3 will test the hypothesis that the FMRP effects on gene expression are dependent on afferent activity. We will examine an inducible deafness mouse model to determine if it can phenocopy the fmr1-KO, indicating that afferent activity is required for FMRP function. The PI has extensive molecular biology experience, and with the guidance of a primary mentor who is a respected RNA biologist. The PI will master current RNA techniques and work towards becoming an independent investigator. Results will reveal how FMRP regulates genes important for auditory development and plasticity. The ultimate goal is to reveal potential therapeutic targets to treat auditory hypersensitivity and processing disorders. The mechanism leading to hyperacusis is poorly understood, and because it is not limited to FXS and affects up to 15% of the population, the study is relevant to the general population.