Identification of Bruno function and direct-targets in muscle development

动物有多种不同功能的肌肉，例如，将泵血的心脏肌肉与允许行走的腿部肌肉进行比较。基因表达的差异和选择性剪接的差异掩盖了功能特性的差异。基因表达模式或选择性剪接模式的中断，如在强直性肌营养不良症(原因剪接因子MBNL和CELF1)和扩张性心肌病(原因剪接因子RBM20)中观察到的那样，会改变肌肉蛋白质的发育表达，导致功能缺陷和肌肉疾病。直到最近才证明剪接因子是肌肉疾病的病因，其复杂的、通常是间接的调控网络使它们在体内研究具有挑战性。因此，肌肉选择性剪接的生理机制以及哪些中断与疾病相关目前还知之甚少。我之前对CELF家族成员Bruno-1的研究建立了果蝇飞行肌肉作为研究肌肉类型特异性选择性剪接的模型。我指出，Bruno-1的缺失会导致肌节生长缺陷和过度收缩。我们仍然不知道Bruno-1是如何调节剪接的，或者它是否调节转录后RNA加工的额外步骤。此外，我们还不知道Bruno-1突变导致肌节缺陷的发育机制。为了回答这些问题，我建议确定在飞行肌肉中Bruno突变肌原纤维缺陷的发育机制，并确定个别Bruno亚型的特定功能。我们将使用iCLIP进一步鉴定Bruno直接靶RNA和结合基序。这将使我们能够在体内研究肌肉类型特异性RNA调控的发育机制和功能，促进我们对选择性剪接的理解，并描述与脊椎动物肌肉疾病病理相关的分子机制。

Animals have multiple types of muscles with distinct functions, for example compare heart muscle that pumps blood to leg muscle that allows ambulation. Differences in gene expression and alternative splicing underly differences in functional properties. Disruptions to patterns of gene expression or alternative splicing, such as those observed in myotonic dystrophy (causal splicing factors MBNL and CELF1) and dilated cardiomyopathy (causal splicing factor RBM20), modify the developmental expression of muscle proteins, resulting in functional defects and muscle disease. It has only recently been demonstrated that splicing factors are causal for muscle disease, and their complex, often indirect regulatory networks make them challenging to study in vivo. Thus, the physiological mechanisms of alternative splicing in muscle as well as which disruptions are disease relevant are currently poorly understood. My previous work on CELF-family member Bruno-1 established Drosophila flight muscle as a model to study muscle-type specific alternative splicing. I showed that loss of Bruno-1 results in sarcomere growth defects and hypercontraction. We still do not understand mechanistically how Bruno-1 regulates splicing or if it regulates additional steps in posttranscriptional RNA processing. In addition, we do not know the developmental mechanisms disrupted in Bruno-1 mutants that cause sarcomere defects. To answer these questions, I propose to identify the developmental mechanisms underlying Bruno mutant myofibril defects in flight muscle, and to identify specific functions for individual Bruno isoforms. We will further identify Bruno direct target RNAs and binding motifs using iCLIP. This will allow us to investigate developmental mechanisms and function of muscle-type specific RNA regulation in vivo, advancing our understanding of alternative splicing and describing molecular mechanisms relevant to vertebrate muscle disease pathologies.