HPS4 protein forms a BLOC-3 complex with HPS1, another <i>HPS</i> gene product, and the complex has been proposed to function as a guanine nucleotide exchange factor (GEF) for RAB32, a member of the Rab small GTPase family (Rab32), and Rab38 (Rab32/38-GEF) and also as a Rab9 effector.
Within 2 d of embryo injection, we created and corrected chocolate missense mutations in the small GTPase RAB38; a regulator of intracellular vesicle trafficking and phenotypic model of Hermansky-Pudlak syndrome.
RAB38 is expressed in melanocytes and it has been shown that a point mutation in the postulated GTP-binding domain of RAB38 is the gene responsible for human Hermansky-Pudlak syndrome.