AHI1 and steroid-resistant nephrotic syndrome: We chose 9 different genes (NPHP1-9) [14] that cause the recessive kidney disorder nephronophthisis (NPHP), 2 genes (AHI1 and MKS3) causing NPHP-like phenotypes, and 2 genes (NPHS1 and 2) that cause steroid resistant nephrotic syndrome (SRNS) [2], as we had access to DNA from worldwide cohorts of patients with these disorders.