To identify the time at which mitochondrial abnormality occurs in cyst-derived cells, we next used immortalized cyst-derived cells established from a single cyst obtained from proximal cortical tubules collected from a patient with ADPKD harboring a heterozygous PKD1 mutation (WT 9-7) (26) and a normal human renal cortical tubular epithelial cell line derived from normal proximal tubule cells (RCTEC-Lotus tetragonolobus agglutinin [RCTEC-LTA]) to investigated this issue in further detail. The gene discussed is PKD1; the disease is autosomal dominant polycystic kidney disease.