Retinal guanylyl cyclase 2 (RETGC2), also known as guanylate cyclase F (GUCY2F), is one of the two guanylyl cyclases responsible for synthesis of cyclic GMP in rod and cone photoreceptors [, ]. Like RETGC1, RETGC2 is regulated intracellularly by GCAP proteins, which in the presence of Ca2+ inhibit its cyclase activity [].