Investigation of the correlation between mildly deleterious mtDNA variations and the clinical progression of multiple sclerosis

Background: Evidence suggests that mitochondrial DNA (mtDNA) variation at a population level may influence susceptibility to, or the clinical progression of Multiple Sclerosis (MS). Objective: To determine if mtDNA population variation is linked to the clinical progress of MS. Methods: Using the complete mtDNA sequences of 217 MS patients, we applied the new ‘variant load’ model, designed as a framework by which to examine the role of mtDNA variation in the context of complex clinical disease. Results: No significant association was detected between mtDNA ‘variant load’ and the clinical measures of progression. Conclusion: Our results show that mtDNA population variation does not play a substantial role in the clinical progression of MS; however, modest effects and/or effects in a subgroup of patients cannot be entirely excluded as a possibility. The results further illustrate the method's applicability to other disease phenotypes, to use in conjunction with quantitative patient measures, to test for a statistical relationship between mildly deleterious mtDNA variation and disease progression.