BRCA1 promotes repair of DNA damage in cochlear hair cells and prevents hearing loss

Cochlear hair cells (HCs) sense sound waves and allow us to hear. Loss of HCs will cause irreversible sensorineural hearing loss. It is well known that DNA damage repair plays a critical role in protecting cells in many organs. However, how HCs respond to DNA damage and how defective DNA damage repair contributes to hearing loss remain elusive. In this study, we showed that cisplatin induced DNA damage in outer hair cells (OHCs) and promoted OHC loss, leading to hearing loss in mice of either sex. Cisplatin induced the expression of Brca1, a DNA damage repair factor, in OHCs. Deficiency of Brca1 induced OHC and hearing loss, and further promoted cisplatin-induced DNA damage in OHCs, accelerating OHC loss. This study provides the first in vivo evidence demonstrating that cisplatin mainly induces DNA damage in OHCs and that BRCA1 promotes repair of DNA damage in OHCs and prevents hearing loss. Our findings not only demonstrate that DNA-damage inducible agent generates DNA damage in postmitotic HCs, but also suggest that DNA repair factors, like BRCA1, protect postmitotic HCs from DNA-damage induced cell death and hearing loss. Significance statement Sensorineural hearing loss is the most severe hearing loss caused by irreversible loss of cochlear hair cells. Hair cells are vulnerable to aging and ototoxic drug. Though DNA damage repair plays a critical role in protecting cells in many organs, it is poorly understood how DNA damage is repaired in hair cells. This study provides the first in vivo evidence demonstrating that cisplatin mainly induces DNA damage in outer hair cells and that BRCA1 promotes repair of DNA damage in outer hair cells and prevents outer hair cell loss as well as hearing loss.