BLOC1S3 and Usher syndrome: Concerning CEP250 involvement in retinal neurodegeneration, previous reports described a close interaction with NEK2 (a centrosomal RP gene)[57,58], and it was also suggested as a modifier gene in an atypical Usher syndrome family where nonsense mutations in CEP250 in homozygosis and in C2orf71 in heterozygosis showed an additive effect[59].