Tuberin deficiency is associated with decreased protein and mRNA of OGG1 expression in kidney tumors. (A) Immunoblot analysis of OGG1 protein expression in normal kidney and kidney tumor from patients with tuberous sclerosis. Decreased OGG1 is associated with decreased tuberin expression in tumor tissue compared to normal tissue. Tubulin was used as loading control. (B) RNA was extracted from kidney or tumor tissue and its integrity tested by formaldehyde/agarose gel electrophoresis. RTPCR was performed using one μg RNA from each sample to synthesize first and second strand DNA. PCR products were analyzed on ethidium bromide stained gel. Band intensity was quantified for each sample on an image analyzer and the ratio of OGG1 to actin was calculated. Histograms represent means ± SE normal kidney samples and kidney tumors from patients with tuberous sclerosis. Significant difference between control and tumor groups is indicated by **P < 0.01.