PDE6B and retinitis pigmentosa 1: One frequently used mouse model of aggressive RP is the RD1 model (Pde6βrd1/rd1), consisting of a mutation in phosphodiesterase 6β subunit found in rods, leading to initial photoreceptor loss by postnatal day (P) 21 and complete degeneration by P60 (Han et al., 2013).