[Inherited retinal dystrophies: contributions of molecular genetics]

Inherited retinal dystrophies are Mendelian neurodegenerative conditions. The mutations of the responsible genes lead both to cell dysfunction and cell death in the retina. The majority of these diseases are responsible for a progressive vision loss ending in almost complete blindness. Recent breakthroughs in molecular genetics technologies (microchips, next generation sequencing) resulted in a much better understanding of these conditions. Their genetic heterogeneity is extremely large, with 191 causal genes disclosed today, knowing that this number will increase in the next years as a significant proportion of cases, especially those with retinitis pigmentosa, do not have mutations in the currently identified genes. A single phenotype is often caused by mutations in several different genes. In addition, exhaustive gene knowledge led to recognize gene-specific clinical features found in several different phenotypes and thus to propose a pathophysiological hypothesis available for experimental testing. Importantly, this vast field of knowledge opens the way to pre-clinical and clinical therapeutic trials, currently increasing exponentially, and eagerly awaited by the patients for whom the only issue until now was ineluctable blindness.