Significant reduction in SLC22A6 (OAT1) mRNA expression was defined in renal biopsy specimens from patients with different types of nephropathy, i.e., lupus nephritis, IgA nephropathy, focal glomerular sclerosis, membranoproliferative glomerulonephritis, membranous glomerulonephropathy, mesangial proliferative glomerulonephropathy, in comparison to the normal controls. The gene discussed is SLC22A6; the disease is IgA glomerulonephritis.