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Bruno 1 regulates cytoskeleton dynamics and a temporal splicing transition to promote myofibril assembly, growth and maturation in Drosophila flight muscle

ABSTRACT: Muscles undergo developmental transitions in gene expression and alternative splicing that are necessary to refine sarcomere structure and contractility. CUG-BP and ETR-3-like (CELF) family RNA binding proteins are important regulators of RNA processing during myogenesis that are misregulated in diseases such as myotonic dystrophy (DM1). In this work we report a function for Bruno 1 (Bru1, Arrest), a CELF1/2 family homolog in Drosophila, during early muscle myogenesis as well as during later stages of sarcomere assembly and myofiber maturation. We identify an imbalance in growth in sarcomere length and width during later stages of development as the mechanism driving abnormal radial growth, myofibril fusion and the formation of hollow myofibrils in bru1 mutant muscle. Molecularly, we characterize a genome-wide transition from immature to mature sarcomere gene isoform expression in flight muscle development that is blocked in bru1 mutants. We performed whole proteome mass spectrometry in control and bru1 mutant muscle to identify changes to the proteome, and correlated these changes to gene expression and exon use gleaned from mRNA-Seq. Our results reveal the conserved nature of CELF function in regulating cytoskeletal dynamics in muscle development, and demonstrate that defective RNA processing due to misexpression of CELF proteins causes wide-reaching structural defects and progressive malfunction of affected muscles that cannot be rescued by late-stage gene replacement.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Drosophila Melanogaster (fruit Fly)

TISSUE(S): Muscle

SUBMITTER: Ignasi Forne

LAB HEAD: Maria L. Spletter, Ph.D.

PROVIDER: PXD043308 | Pride | 2024-03-08

REPOSITORIES: Pride

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