Esrp1 and Esrp2 Regulate the Stability of<i>tmc1</i>/<i>2a</i>mRNAs 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 <i>ESRP1</i> gene have been associated with sensorineural hearing loss in humans. In <i>Esrp1</i> knockout mouse embryos, alternative splicing of its target genes such as <i>Fgfr2</i> is impaired, which eventually result in cochlear development deficits. However, <i>Esrp1</i> 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 <i>esrp1</i> and its paralog <i>esrp2</i> 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 <i>esrp1/2</i> double knockout larvae. Among the dysregulated genes are <i>tmc1</i> and <i>tmc2a</i>, which encode essential subunits of the MET complex. Further investigations demonstrated that Esrp1/2 could directly bind to <i>tmc1</i> and <i>tmc2a</i> 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 <i>tmc1</i> and <i>tmc2a</i> mRNAs.<b>Significance statement</b> ESRP1 is an important RNA-binding protein, whose malfunction has been associated with hearing loss in humans. <i>Esrp1</i> knockout affects alternative splicing of its target mRNAs such as <i>Fgfr2,</i> eventually leading to cochlear development deficits in mice. However, <i>Esrp1</i> 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 <i>esrp1</i> and its paralog <i>esrp2</i> are expressed in the zebrafish inner ear, and that <i>esrp1</i>/<i>esrp2</i> double knockout compromised the mechano-electrical transduction (MET) function of hair cells. Additionally, we successfully identified <i>tmc1</i> and <i>tmc2a</i> mRNAs as the targets of Esrp1/2, which encode essential subunits of the MET complex.