Genetic diversity of Usher syndrome in Moroccan patients.

Usher syndrome (USH) is a rare genetic disorder accounting for almost 50% of all hereditary deaf-blindness cases. This heterogeneous, autosomal recessive condition is categorized into 3 main clinical subtypes (USH1, USH2 and USH3) and an atypical form of USH based on the severity and age of onset of the hearing loss, the absence or presence of vestibular dysfunction and the age of retinitis pigmentosa (RP) onset. This study aims to characterize the genetic spectrum of Usher syndrome in the Moroccan population. We used targeted-exome, whole exome and Sanger sequencing to identify variants in USH genes. We identified 25 variants among which 6 novel ones with 22 variants in USH1, 3 in USH2 while none were identified in USH3. Twenty-eight out of 33 families had USH1 and 5 out of 33 had USH2. MYO7A is the most prevalent gene mutated in this study with a recurrent splice acceptor site variant c.2283-1G > T found in 7 families. Our findings contribute to the understanding of the genetic diversity of USH in the Moroccan and North African populations, and emphasize the importance of genetic screening in identifying novel variants and providing an early clinical diagnosis to establish a medical follow-up and genetic counseling.