OPA1 and auditory neuropathy: Molecular investigations revealed that haploinsufficiency of Opa1 is the disease causing mechanism leading to impaired mitochondrial dynamics, early increased mitophagy and autophagy, and subsequently an age-related increase in mtDNA depletion accumulation, oxidative stress, impaired autophagic flux, and pro-apoptotic death, prompting together the age-related ANSD.