Furthermore, while Rpgrip1nmf247/nmf247 and Rpgrip1l+/− mouse embryos do not show any defects (Vierkotten et al, 2007; Won et al, 2009; Gerhardt et al, 2013), their combined mutations induce polycystic kidneys in Rpgrip1l+/−; Rpgrip1nmf247/nmf247 embryos (Fig 7B and C) demonstrating a functional synergy of Rpgrip1l and Rpgrip1 in renal development. This evidence concerns the gene RPGRIP1 and polycystic kidney disease.