Table 1.

Types of Connexin26 (Cx26) and Cx30 human mutations and their possible treatment windows and outcomes by cochlear gene therapy.

Type of hearing loss	Mutation examples	Possible time window of treatment	Possible outcome
Late onset of mild hearing loss	Cx26: V37I, M34T, C202F, etc., Cx30: M203V, etc.,	Broad time window, possibly even after onset of hearing loss.	Complete recovery.
Syndromic hearing loss	Cx26: D66H, Y65H, G59A, G45E, D50N, H73R and N54K, etc., Cx30: G11R, A88V, etc.,	Embryonic (before W20)/early postnatal, likely need to be before the manifestation of hearing loss.	Uncertain treatment efficacy based on mouse model studies.
Non-syndromic hearing loss	Cx26: 35delG, 167delT, W44S, R75W, and R75Q, etc., Cx30: T5M, 342-KB DEL, etc.,	Embryonic (before W20)/Postnatal treatment needed.	Partial recovery of hearing. However, treatment benefit vs. risk is debatable.