Cytoplasmic Functions of Rbfox1, a Candidate Autism Gene

描述（由申请人提供）：神经元内RNA加工和翻译的异常可能导致自闭症谱系障碍（ASD）。例如，脆性X智力迟钝蛋白（一种参与突触处RNA运输和翻译调节的RNA结合蛋白）的突变代表了ASD最常见的单基因原因。最近，人类遗传学研究确定RNA结合蛋白Rbfox 1（也称为A2 BP 1）是另一个候选自闭症基因。Rbfox 1结合一个明确定义的RNA序列（U）GCAUG，并在细胞核中作为RNA剪接的调节因子发挥作用。Rbfox 1本身被选择性地剪接成细胞核和细胞质形式。我们发现，细胞质Rbfox 1定位于小鼠海马神经元的树突和突触。许多神经元RNA在其3'非翻译区（3' UTR）中含有保守的（U）GCAUG片段，我们的数据表明，细胞质Rbfox 1调节这些mRNA的稳定性和/或翻译。此外，我们的实验表明，Rbfox 1通过干扰microRNA（miRNA）介导的一些靶mRNA的翻译抑制来调节翻译。细胞质Rbfox 1的许多mRNA靶点已被鉴定为Rbfox 1在自闭症受试者大脑中下调的基因模块中的靶点。我们认为神经元中mRNA稳定性和翻译的失调是ASD病理生理学的重要组成部分。我们的建议旨在1）确定Rbfox 1的细胞质定位mRNA靶点，并确定Rbfox 1调节其稳定性和/或翻译的机制。我们提出的研究结果可能揭示神经发育障碍（包括自闭症谱系障碍）中神经回路功能障碍的基本细胞生物学机制和特定分子靶点。

DESCRIPTION (provided by applicant): Abnormalities in RNA processing and translation within neurons likely contribute to Autism Spectrum Disorders (ASD). For example, mutations in Fragile X Mental Retardation protein, an RNA binding protein involved in RNA trafficking and translational regulation at the synapse, represent the most common single gene cause of ASD. More recently, human genetic studies identified the RNA binding protein Rbfox1 (also known as A2BP1) as another candidate autism gene. Rbfox1 binds a well-defined RNA sequence, (U)GCAUG, and functions in the nucleus as a regulator of RNA splicing. Rbfox1 itself is alternatively spliced into nuclear and cytoplasmic forms. We show that cytoplasmic Rbfox1 localizes to dendrites and synapses in mouse hippocampal neurons. Many neuronal RNAs contain conserved (U)GCAUG stretches in their 3' untranslated regions (3'UTRs), and our data indicate that cytoplasmic Rbfox1 regulates the stability and/or translation of these mRNAs. In addition, our experiments suggest that Rbfox1 regulates translation by interfering with microRNA (miRNA)-mediated translational repression of some target mRNAs. Many of the mRNA targets of cytoplasmic Rbfox1 have been identified as targets of Rbfox1 in a module of genes that are down regulated in brains of autistic subjects. We propose that dysregulation of mRNA stability and translation in neurons is an important component of the pathophysiology of ASD. Our proposal is aimed at 1) identifying the cytoplasmically localized mRNA targets of Rbfox1 and at 2) determining the mechanisms whereby Rbfox1 regulates their stability and/or translation. The results of our proposed studies may reveal fundamental cell biological mechanisms and specific molecular targets that underlie neural circuit dysfunction in neurodevelopmental disorders, including Autism Spectrum Disorders.