Identification of Bruno function and direct-targets in muscle development

• Applicant: Professorin Maria Spletter, Ph.D.
• Subject Area: Developmental Biology ; General Genetics and Functional Genome Biology ; Biochemistry
• Term: from 2019 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 417912216

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.

• DFG Programme: Research Grants