Usher Syndrome: Ocular Genetic Studies

Usher syndrome (USH) is the most common form of syndromic deaf-blindness and is classified as a syndromic ciliopathy. It is characterized by sensorineural hearing loss, retinitis pigmentosa (RP), and, in some cases, vestibular dysfunction. USH is inherited in an autosomal recessive manner and presents in three distinct clinical subtypes: USH type 1 (USH1), type 2 (USH2), and type 3 (USH3). The estimated prevalence of USH ranges between 3 and 6 per 100,000 individuals worldwide. The syndrome is known for its clinical and genetic heterogeneity, with 13 genes currently identified as causative. At the molecular level, USH-related proteins are highly expressed in the periciliary region of retinal photoreceptors. This protein network is essential for maintaining the structural integrity of the photoreceptor cilium and facilitating intracellular transport between the inner and outer segments of photoreceptor cells. Disruption of these processes leads to progressive photoreceptor degeneration and vision loss, hallmark features of retinitis pigmentosa.