Naa80 is required for actin N-terminal acetylation and normal hearing in zebrafish

Actin is a critical component of the eukaryotic cytoskeleton. In animals, actins undergo unique N-terminal processing by dedicated enzymes resulting in mature acidic and acetylated forms. The final step, N-terminal acetylation, is catalyzed by NAA80 in humans. N-terminal acetylation of actin is crucial for maintaining normal cytoskeletal dynamics and cell motility in human cell lines. However, the physiological impact of actin N-terminal acetylation remains to be fully understood. We developed a zebrafish <i>naa80</i> knockout model and demonstrated that Naa80 acetylates both muscle and non-muscle actins in vivo. Assays with purified Naa80 revealed a preference for acetylating actin N-termini. Zebrafish lacking actin N-terminal acetylation exhibited normal development, morphology, and behavior. In contrast, humans with pathogenic actin variants can present with hypotonia and hearing impairment. Whereas zebrafish lacking <i>naa80</i> showed no obvious muscle defects or abnormalities, we observed abnormal inner ear development, small otoliths, and impaired response to sound. In conclusion, we have established that zebrafish Naa80 N-terminally acetylates actins in vitro and in vivo, and that actin N-terminal acetylation is essential for normal hearing.