The function of this compartment is poorly understood, but human or mouse mutations in genes encoding components of the INVS compartment, INVS/NPHP2, NPHP3 and ANKS6/NPHP16, are known to lead to infantile nephronophthisis with cystic kidneys, congenital heart defects and laterality defects [9–13]. The gene discussed is INVS; the disease is nephronophthisis.