Biology subjects

Cooper, T. A.

Publications and source records attributed to Cooper, T. A..

3 recordsLinked to original sources

bioRxiv2022

The role of Limch1 alternative splicing in skeletal muscle function

Postnatal skeletal muscle development is a highly dynamic period associated with extensive transcriptome remodeling. A significant aspect of postnatal development is widespread alternative splicing changes, required for the adaptation of tissues to adult function. These splicing events have significant implications since the reversion of adult mRNA isoforms to fetal isoforms is observed in forms of muscular dystrophy. LIM and Calponin Homology Domains 1 (LIMCH1) is a stress fiber associated protein that is alternative spliced to generate uLIMCH1, a ubiquitously expressed isoform, and mLIMCH1, a skeletal muscle-specific isoform. mLIMCH1 contains 454 in-frame amino acids which are encoded by six contiguous exons simultaneously included after birth in mouse. The developmental regulation and tissue specificity of this splicing transition is conserved in mice and humans. To determine the physiologically relevant functions of mLIMCH1 and uLIMCH1, CRISPR-Cas9 was used to delete the genomic segment containing the six alternatively spliced exons of LIMCH1 in mice, thereby forcing the constitutive expression of the predominantly fetal isoform, uLIMCH1 in adult skeletal muscle. mLIMCH1 knockout mice had significant grip strength weakness in vivo and maximum force generated was decreased ex vivo. Calcium handling deficits were observed during myofiber stimulation that could explain the mechanism by which mLIMCH1 knockout leads to muscle weakness. Additionally, LIMCH1 is mis-spliced in myotonic dystrophy type 1 with the muscle blind-like (MBNL) family of proteins acting as the likely major regulator of Limch1 alternative splicing in skeletal muscle.

molecular biology↗

bioRxiv2019

Overexpression of a non-muscle RBFOX2 isoform triggers cardiac conduction defects in myotonic dystrophy

Myotonic dystrophy type 1 (DM1) is a multisystemic genetic disorder caused by a CTG trinucleotide repeat expansion in the 3' untranslated region of DMPK gene. Heart dysfunctions occur in nearly 80% of DM1 patients and are the second leading cause of DM1-related deaths. Despite these figures, the mechanisms underlying cardiac-based DM1 phenotypes are unknown. Herein, we report that upregulation of a non-muscle splice isoform of RNA binding protein RBFOX2 in DM1 heart tissue--due to altered splicing factor and microRNA activities--induces cardiac conduction defects in DM1 individuals. Mice engineered to express the non-muscle RBFOX2 isoform in heart via tetracycline-inducible transgenesis, or CRISPR/Cas9-mediated genome editing, reproduced DM1-related cardiac-conduction delay and spontaneous episodes of arrhythmia. Further, by integrating RNA binding with cardiac transcriptome datasets from both DM1 patients and mice expressing the non-muscle RBFOX2 isoform, we identified RBFOX2-driven splicing defects in the voltage-gated sodium and potassium channels, which can alter their electrophysiological properties. Thus, our results uncover a trans-dominant role for an aberrantly expressed RBFOX2 isoform in DM1 cardiac pathogenesis.

genetics↗

bioRxiv2018

Rbfox splicing factors maintain skeletal muscle mass by regulating calpain3 and proteostasis

Alternative splicing promotes proteomic diversity important for cellular differentiation and cell fate determination. Here, we show that deletion of the highly conserved Rbfox1 and Rbfox2 alternative splicing regulators in adult mouse skeletal muscle causes rapid, severe loss of muscle mass. Homeostasis of skeletal muscle tissue requires a dynamic balance between protein synthesis and degradation (proteostasis) but the mechanisms that regulate this balance are not well understood. Rbfox deletion did not cause reduced global protein synthesis, but resulted in reduced autophagy flux and altered splicing of hundreds of transcripts including Capn3, which produced an active form of calpain3 protease. The results indicate Rbfox proteins regulate proteostasis in skeletal muscle tissue by control of calpain and autophagy-lysosome pathways.\n\nHighlightsO_LIProteostasis in adult skeletal muscle is post-transcriptionally regulated, in part by alternative splicing via Rbfox1/2\nC_LIO_LIRbfox1/2 regulate hundreds of targets in skeletal muscle, including Calpn3, to maintain muscle mass in adult mice\nC_LIO_LIAutophagy flux is markedly decreased in muscle lacking Rbfox1/2\nC_LIO_LIAs for neurons, altered proteostasis is detrimental to adult muscle\nC_LI

molecular biology↗