BLOC1S3 and retinitis pigmentosa 1: While P23H-Rho is a class 2 autosomal dominant RP mutation that misfolds and causes ER retention, R135L-Rho is a class 3 RP mutation that causes mutant protein accumulation in the endocytic pathway (Aguilà et al., 2014; Athanasiou et al., 2018; Chuang et al., 2004).