Table 3.

Genes proposed to underlie age-related hearing loss in humans

Gene	Mutation	Proposed Gene Function	Reference
ACTG1	DFNA20/26	hair cell maintenance and repair	(Zhu et al., 2003)
COCH	DFNA9	extracellular matrix	(de Kok et al., 1999)
DFNA5	DFNA5	unknown	(Van Laer et al., 2002)
GRHL2	DFNA28 intron 1 SNP	cochlear epithelial cell maintenance?	(Van Laer et al., 2008)
GRM7	SNPs	susceptibility to glutamate excitotoxicity	(Friedman et al., 2008)
KCNQ4	DFNA2 SNPs	potassium recycling, regulation of OHC depolarization	(Kubisch et al., 1999; Van Eyken et al., 2006)
mtDNA genes	several	energy metabolism, oxidative stress	(Fischel-Ghodsian, 1999)
NAT2	SNPS	detoxification of reactive oxygen species	(Unal et al., 2005; Van Eyken et al., 2007)