This is also true of other ciliopathies, for example, where mutations in TTC21B (which encodes IFT139) can cause both isolated nephronophthisis and syndromic Jeune asphyxiating thoracic dystrophy as well as showing extensive genetic interactions with other ciliopathy loci (Davis et al., 2011). The gene discussed is TTC21B; the disease is nephronophthisis.