# CELF1 Downregulation Promotes Cardiomyocyte Hypertrophy via Regulating Alternative Splicing of Tead1

## TL;DR

This study shows that reducing CELF1 in heart muscle cells leads to cell enlargement and changes in how the Tead1 gene is spliced, which may contribute to heart disease.

## Contribution

The novel finding is that CELF1 regulates cardiomyocyte hypertrophy through alternative splicing of Tead1, involving interactions with hnRNPC and m6A modifications.

## Key findings

- CELF1 knockdown increases cardiomyocyte size and upregulates hypertrophic markers.
- CELF1 knockdown shifts Tead1 splicing from the long isoform (Tead1-L) to the short isoform (Tead1-S).
- CELF1 interacts with hnRNPC and influences global m6A abundance in HeLa cells.

## Abstract

Background/Objectives: The RNA-binding protein CELF1 is crucial for cardiac development, but its role in cardiomyocyte hypertrophy is unclear. This study investigates the effects of acute CELF1 knockdown on alternative splicing and hypertrophic growth in cardiomyocytes. Methods: Neonatal rat cardiomyocytes (NRCMs) were transfected with two siRNAs targeting CELF1. Hypertrophy was assessed by cell size and expression of hypertrophic markers via qPCR and Western blot. RNA sequencing was performed in NRCMs to identify alternative splicing events. Tead1 function was tested by knockdown in NRCMs. Selected mechanistic assays were performed primarily in HeLa cells. Results: CELF1 knockdown in NRCMs increased cardiomyocyte size and upregulated hypertrophic markers, while its overexpression restored the phenotype. RNA-seq revealed that CELF1 knockdown alters the alternative splicing pattern. Specifically, the splicing of the transcription factor Tead1 shifted from the full-length long Tead1 isoform (Tead1-L) to the exon 4-skipped short isoform (Tead1-S). In HeLa cells, CELF1 interacted with hnRNPC, an m6A reader and splicing factor, and CELF1 perturbation correlated with changes in global m6A abundance. Conclusions: These findings suggest that CELF1 regulates hypertrophic phenotypes in cardiomyocytes and is associated with alternative splicing of Tead1.