Esrp1 and Esrp2 regulate the stability oftmc1/2amRNAs in zebrafish sensory hair cells

RNA-binding proteins (RBPs) are important for post-transcriptional RNA processing, including pre-mRNA alternative splicing, mRNA stability, and translation. Several RBPs have been shown to play pivotal roles in the inner ear, whose dysfunction leads to auditory and/or balance impairments. Epithelial splicing-regulatory protein 1 (ESRP1) regulates alternative splicing and mRNA stability, and mutations in ESRP1 gene have been associated with sensorineural hearing loss in humans. In Esrp1 knockout mouse embryos, alternative splicing of its target genes such as Fgfr2 is impaired, which eventually result in cochlear development deficits. However, Esrp1 knockout mice die soon after birth because of complications from cleft-lip and palate defects, impeding further investigations at later postnatal ages. In the present study, we explored the role of ESRP1 in hearing using zebrafish as a model. We showed that esrp1 and its paralog esrp2 are expressed in the inner ear and certain anterior lateral line (ALL) neuromasts. Furthermore, our data suggested that Esrp1 and Esrp2 are required for the mechano-electrical transduction (MET) function of hair cells. RNA sequencing results indicated a significant decrease in the levels of several mRNAs in esrp1/2 double knockout larvae. Among the dysregulated genes are tmc1 and tmc2a , which encode essential subunits of the MET complex. Further investigations demonstrated that Esrp1/2 could directly bind to tmc1 and tmc2a mRNAs and affect their stability. Taken together, we showed here that Esrp1 and Esrp2 regulate the MET function of zebrafish sensory hair cells by modulating the stability of tmc1 and tmc2a mRNAs. Significance statement ESRP1 is an important RNA-binding protein, whose malfunction has been associated with hearing loss in humans. Esrp1 knockout affects alternative splicing of its target mRNAs such as Fgfr2, eventually leading to cochlear development deficits in mice. However, Esrp1 knockout mice die soon after birth, precluding further investigations at later postnatal ages. In this study, we explored the role of ESRP1 in hearing using zebrafish as a model. Our results demonstrated that esrp1 and its paralog esrp2 are expressed in the zebrafish inner ear, and that esrp1 / esrp2 double knockout compromised the mechano-electrical transduction (MET) function of hair cells. Additionally, we successfully identified tmc1 and tmc2a mRNAs as the targets of Esrp1/2, which encode essential subunits of the MET complex.