Usher syndrome (USH) is the most frequent hereditary cause of deafness associated to blindness. It is a rare disease, affecting 1 in every 10.000 individuals, with an autosomal recessive monogenic inheritance. Deafness is congenital while the retinitis pigmentosa is not detected before the age of 8 to 10. These patients suffer from a dreadful disability as their two major senses are impaired. Important scientific advances have been achieved, mostly by auditory scientists: 9 causative genes have been identified. The hearing impairment pathogenesis has been elucidated, ie, an early developmental defect of auditory sensory cells. Our project gathering scientists and physicians from both the auditory and visual fields aims : -to halt the no longer acceptable underdiagnosis of this syndrome. Because, children affected with Usher type I, the most severe form, are usually diagnosed as severely or profoundly deaf only, parents may choose visual/sign language whereas these children would have taken full advantage from an early cochlear implantation. -To make these patients benefit from gene replacement therapy in the retina that recently showed tremendous results. We propose : 1/ To develop new clinical and molecular tools and guidelines for an early diagnosis thereafter broadly disseminated. 2/To clarify the retinal pathogenesis of Usher syndrome (type I and II) by an unpreceding effort to generate animal and tissue models that will be characterised in depth by multidisciplinary investigations including innovative methods. Mouse, frog, pig in vivo models and cultured retinal explants will be used, as well as human retinal cultures. This will also provide the necessary tests to evaluate phenotype rescuing. 3/To prevent and treat the retinal defect by associated adenovirus (AAV) gene therapy. This includes optimisation of the gene transfer and selection of patients to lead to a clinical trial carried out for one or more Usher genes (USH1B, 1C, 1G & USH2D)