CELF1, PTBP1, and RBFOX2-mediated alternative splicing regulation in cardiovascular diseases


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Alternative splicing (AS) is dysregulated in Type 1 diabetic (T1D) and hypoplastic left heart syndrome (HLHS) patient hearts but the mechanisms responsible are unclear. Here, we provide evidence that in these patient’s hearts that dysregulation of the RNA binding proteins (RBPs) CELF1, PTBP1, and RBFOX2 contribute to AS changes. Utilizing genome-wide approaches, we identified extensive changes in AS patterns in T1D mouse hearts. We discovered that many aberrantly spliced genes in T1D hearts have CELF1 and PTBP1 binding sites. CELF1-regulated AS affects key genes within signaling pathways relevant to diabetes pathogenesis. Disruption of CELF1 binding sites impairs AS regulation by CELF1. We show that a spliced variant of PTBP1 that is highly expressed in normal newborn mouse hearts is aberrantly expressed in adult T1D mouse hearts. We also demonstrated that inducible expression of diabetes-induced PTBP1 spliced variant has less repressive splicing function. Notably, PTBP1 antagonizes RBFOX2-mediated AS of selected mRNA targets in this context. In summary, our results indicate that CELF1 and PTBP1 target RNAs are aberrantly spliced in the T1D heart, leading to abnormal gene expression.

RBFOX2 is significantly associated with HLHS. In HLHS, three damaging de novo RBFOX2 mutations (nonsense, frameshift, and splice site) have been identified. Here we provide evidence that the nonsense and frameshift RBFOX2 mutants are unable to promote proper splicing of their target genes despite normal subcellular localization of these mutants. Further, we show that the nonsense mutant interacts with a subset of proteins that wildtype RBFOX2 does not interact with, indicating that this nonsense mutant may constitute a gain of function. These discoveries pave the way for targeting RBPs and their RNA networks as novel therapies for cardiac complications of diabetes and HLHS.



Alternative splicing, RNA binding proteins, RBFOX2, CELF1, PTBP1