Recent studies of human deafness genes gave a great impact on auditory medicine. Namely, genetic deafness affects about 1 in 2, 000 children and one to thirds of deafness patients are related to gene mutations. However, without an animal model for hereditary deafness, it is quite difficult to determine the anatomical, biochemical, and cellular basis for the phenotype, or to use gene rescue to prove unequivocally that the disease-causing gene has been identified. Here, I introduced two types of mouse models of
gjb2 mutation. First, transgenic mice expressing a mutant connexin26 with R75W mutation identified in a deaf family with autosomal dominant inheritance was generated. Two lines of transgenic mice showed severe to profound hearing loss, deformity of supporting cells, failure in the formation of the tunnel of Corti, and degeneration of sensory hair cells. Despite robust expression of the transgene, no obvious structural change was observed in the stria vascularis or spiral ligament that is rich in connexin26 and generates the endolymph. The high resting potential in cochlear endolymph essential for hair cell excitation was normally sustained. Second, In order to confirm pathogenesis of
Gjb2 mutation in recessive form, targeted disruption of
Gjb2 using Cre recombinase controlled by PO was carried out. Targeted disruption of
Gjb2 caused profound deafness from birth but has never reach maturation. Apparent degeneration of the organ of Corti was recognized, together with presumably secondary reduction of numbers of spiral ganglion cells. These findings confirmed a crucial role of
Gjb2 in the cochlear function. Thus, development of animal models of non-syndromic deafness will provide us with a promising tool to create fundamental therapies and thereby to enable to rescue the impaired hearing.
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