From analysis of hypervariable sequence I, which is located in the non-coding region of mitochondrial DNA (mtDNA), we previously reported that mitochondrial haplogroups (mtHAPs) G1 and F were associated with elite Japanese endurance/middle-power and sprint/power athlete status, respectively (Mikami et al, Br J Sport Med, 2010 [Epub ahead of print]). The purpose of the present study was to identify functional polymorphisms specific to mtHAPs G1 and F in elite Japanese athletes. We directly sequenced the entire mtDNA of 96 Japanese Olympians from a variety of sports, and identified mtHAPs G1- and F-specific polymorphisms in the coding region. mtHAP G1 was characterized by 4 such polymorphisms: m.7867C>T, m.8200T>C, m.15323G>A and m.15497G>A. Two polymorphisms (m.15323G>A and m.15497G>A) were non-synonymous substitutions (Ala193Thr and Gly251Ser, respectively) in cytochrome b. mtHAP F was also characterized by 4 coding region polymorphisms: m.3970C>T, m.6392T>C, m.10310G>A and m.13928G>C. One of the polymorphisms (13928G>C) causes an amino acid replacement (Ser531Thr) in the NADH dehydrogenase subunit 5. Two mtHAP G1-specific and 1 mtHAP F-specific functional polymorphisms have been identified as candidates to mediate the recent association between these mtHAPs and elite Japanese athlete status. Exercise performance is influenced not only by mtDNA polymorphisms, but also by nuclear DNA polymorphisms. We plan to investigate both nuclear and mitochondrial polygenic profiles of elite Japanese athletes.
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