Knockout of dhx38 Causes Inner Ear Developmental Defects in Zebrafish

Background: Alternative splicing is essential for the physiological and pathological development of the inner ear. Disruptions in this process can result in both syndromic and non-syndromic forms of hearing loss. DHX38, a DEAH box RNA helicase, is integral to pre-mRNA splicing regulation and plays critical roles in development, cell differentiation, and stem cell maintenance. However, its specific role in inner ear development remains undefined. Here, we utilized a dhx38 knockout zebrafish model to monitor the ear morphology and elucidate a crucial role for DHX38 in the development of the zebrafish inner ear. Methods: Bright-field morphological analysis and in situ hybridization were performed to observe ear morphology changes. Immunofluorescence and semi-quantitative RT-PCR were employed to test apoptotic cells and abnormal splicing. Results: The dhx38-/- mutant zebrafish showed significant inner ear impairments, including decrescent otocysts, absent semicircular canal protrusion, and smaller otoliths. These structural abnormalities were accompanied by substantial DNA damage and p53-dependent apoptosis within the inner ear cells. Alternative splicing analysis showed that genes related to DNA damage repair and inner ear morphogenesis are abnormal in dhx38 knockout mutants. In summary, we suggest that dhx38 promotes cell survival during the inner ear development of zebrafish by ensuring the correct splicing of genes related to DNA damage repair.