G protein-coupled receptors (GPRs or GPCRs), are members of the largest protein family and play a role in many different stimulus-response pathways. G-protein coupled receptors mediate extracellular signals into intracellular signals (G-protein activation). They respond to a great variety of signaling molecules, including hormones, neurotransmitters and other proteins and peptides. GPR143, also designated ocular albinism type 1 protein (OA1), is detected exclusively in pigment cells. OA1, which is a multi-pass membrane protein, is a melanosomal protein expressed primarily in pigment cells. Defects in the gene encoding for OA1 cause ocular albinism, an X-linked disorder mainly characterized by retinal hypopigmentation and visual impairment.