A PDEδ knockout mouse develops a more subtle phenotype with a slowly progressive rod-cone dystrophy together with mislocalisation of prenylated phototransduction proteins such as rhodopsin kinase (GRK1) and the catalytic subunits of rod and cone cyclic GMP phosphodiesterase (PDE6) (Zhang et al., 2007). The gene discussed is GRK1; the disease is Cone rod dystrophy.