NPHP4 and Bardet-Biedl syndrome: Mouse Nphp4n/nBbs1-/- double mutant embryos survived through the end of embryogenesis with no gross abnormalities, similar to each single mutant (S4B Fig), indicating that, in contrast to the genetic interaction between nphp-4 and a BBS-associated gene in C. elegans, there is no strong genetic interaction between mouse Nphp4 and Bbs1.