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Rbfox1 controls alternative splicing of focal adhesion genes in cardiac muscle cells
Peter Zorn1,† , Jaime Calvo Sánchez1,† , Tala Alakhras1 , Barbara Schreier2 , Michael Gekle2 , Stefan Hüttelmaier3 , Marcel Köhn1,*
1Junior Group ‘Non-coding RNAs and RBPs in Human Diseases’, Medical Faculty, University of Halle–Wittenberg, 06120 Halle (Saale), Germany
2Julius Bernstein Institute of Physiology, Medical Faculty, University of Halle–Wittenberg, 06112 Halle (Saale), Germany
3Institute of Molecular Medicine, Medical Faculty, University of Halle–Wittenberg, 06120 Halle (Saale), Germany
These authors contributed equally to this work
*Correspondence to:Marcel Köhn , Email:marcel.koehn@medizin.uni-halle.de
J Mol Cell Biol, Volume 16, Issue 1, January 2024, mjae003,  https://doi.org/10.1093/jmcb/mjae003
Keyword: Rbfox1, alternative splicing, focal adhesion, cardiac muscle cells

Alternative splicing is one of the major cellular processes that determine the tissue-specific expression of protein variants. However, it remains challenging to identify physiologically relevant and tissue-selective proteins that are generated by alternative splicing. Hence, we investigated the target spectrum of the splicing factor Rbfox1 in the cardiac muscle context in more detail. By using a combination of in silico target prediction and in-cell validation, we identified several focal adhesion proteins as alternative splicing targets of Rbfox1. We focused on the alternative splicing patterns of vinculin (metavinculin isoform) and paxillin (extended paxillin isoform) and identified both as potential Rbfox1 targets. Minigene analyses suggested that both isoforms are promoted by Rbfox1 due to binding in the introns. Focal adhesions play an important role in the cardiac muscle context, since they mainly influence cell shape, cytoskeletal organization, and cell–matrix association. Our data confirmed that depletion of Rbfox1 changed cardiomyoblast morphology, cytoskeletal organization, and multinuclearity after differentiation, which might be due to changes in alternative splicing of focal adhesion proteins. Hence, our results indicate that Rbfox1 promotes alternative splicing of focal adhesion genes in cardiac muscle cells, which might contribute to heart disease progression, where downregulation of Rbfox1 is frequently observed.