MOUSE MODEL FOR USHER SYNDROME - LINKAGE MAPPING SUGGESTS HOMOLOGY TOUSHER TYPE-I REPORTED AT HUMAN-CHROMOSOME 11P15

Usher syndrome is a group of diseases with autosomal recessive inherit ance, congenital hearing loss, and the development of retinitis pigmen tosa, a progressive retinal degeneration characterized by night blindn ess and visual field loss over several decades. The causes of Usher sy ndrome are unknown and no animal models have been available for study. Four human gene sites have been reported, suggesting at least four se parate forms of Usher syndrome, We report a mouse model of type I Ushe r syndrome, rd5, whose linkage on mouse chromosome 7 to Hbb and tub ha s homology to human Usher I reported on human chromosome 11p15. The el ectroretinogram in homozygous rd5/rd5 mouse is never normal with reduc ed amplitudes that extinguish by 6 months. Auditory-evoked response te sting demonstrates increased hearing thresholds more than control at 3 weeks of about 30 decibels (dB) that worsen to about 45 dB by 6 month s.