S SARAVANABAVAN 1,2, A MUNT 1,2, A WONG 1,2, G RANGAN 1,2
1Centre for Transplant and Renal Research, Westmead Institute for Medical Research, The University of Sydney, Westmead , Australia, 2Department of Renal Medicine, Westmead Hospital, Westmead, Australia
Aim: To determine whether variations in peripheral blood mitochondrial DNA (mtDNA) copy number predicts disease severity in ADPKD.
Background:Polycystin proteins directly regulate mitochondrial function and contribute to the mechanisms of disease progression in ADPKD. MtDNA copy number is also reduced in a PKD1 dose-dependent manner in ADPKD and therefore may be a predictor of disease severity.
Methods: DNA was extracted from peripheral blood from individuals with ADPKD and a quantitative duplex PCR assay was developed to determine the number of copies of the mitochondrial gene, tRNA leucine (tRNAleu) relative to the nuclear gene, beta-2-microglobulin (B2M). A pooled DNA sample was used for assay optimization and standardization.
Results: The mean amplification efficiency of the PCR assay was 96.7% and 92.6% respectively for B2M and tRNAleu. The minimal range of detection of mtDNA relative to a single copy of B2M was between 10 and 10000 copies. As a pilot analysis, DNA from two individuals with a mild and severe disease phenotype was used to evaluate the functionality of the assay. The results showed that the mtDNA copies were higher in an individual with Mayo Subclass 1A (male, age 35 years, eGFR 110 ml/min/1.73m2) compared to the individual with Mayo Subclass 1E (male, age 38 years, eGFR 56 ml/min/1.73m2) (619 vs. 148 relative mtDNA copies respectively).
Conclusion:The preliminary data suggest that higher mtDNA copy number is associated with less severe disease in ADPKD. These findings warrant further evaluation in a larger cohort.
Sayanthooran Saravanabavan is a Postdoctoral Fellow in Polycystic Kidney Disease at the Centre for Transplant and Renal Research, Westmead Institute for Medical Research, The University of Sydney. His work currently focuses on understanding the role of the DDR in acute kidney injury repair and ADPKD progression. In addition, he is testing the potential use of peripheral blood mitochondrial DNA as a prognostic biomarker in ADPKD.