To determine the roles of GSR in the antioxidant defense in the cochlea of mice under normal physiological conditions, Gsr+/- mice were backcrossed for 6 generations onto the CBA/CaJ mouse strain, a normal-hearing strain that does not carry a specific Cdh23 mutation that causes progressive hair cell degeneration and early onset of hearing loss [22]. Here, GSR is linked to hearing loss disorder.