A new mitochondrial DNA mutation at 14577 T/C is probably a major pathogenic mutation for maternally inherited type 2 diabetes.

  1. M Tawata,
  2. J I Hayashi,
  3. K Isobe,
  4. E Ohkubo,
  5. M Ohtaka,
  6. J Chen,
  7. K Aida and
  8. T Onaya
  1. Third Department of Internal Medicine, Yamanashi Medical University, Tamaho, Japan. tawatam@res.yamanashi-med.ac.jp

    Abstract

    From a family of 16 diabetic patients with typical maternal inheritance, we investigated a 69-year-old woman with type 2 diabetes. The proband showed no major deletions in the mitochondrial DNA (mtDNA). Direct sequencing revealed 7 missense and 5 ribosomal RNA homoplasmic nucleotide substitutions when compared with the Cambridge Sequence and its recent revision. When compared with the control cybrid cells, the proband cybrid cells showed 6 nucleotide substitutions. Among these, 14577 T/C, which turned out to be 98.9% heteroplasmic, is a new missense substitution in the NADH dehydrogenase 6 gene. We also observed 2 other patients with 14577 T/C substitution from another group of 252 unrelated diabetic patients, whereas no individual from a group of 529 control subjects had 14577 T/C substitution. Furthermore, these 6 substitutions were in linkage disequilibrium. Mitochondrial respiratory chain complex I activity and O2 consumption rates of the proband cybrid cells, which were obtained by the fusion of mtDNA-deleted (rho0) HeLa cells and mtDNA from the proband, showed 64.5 and 61.5% reductions, respectively, compared with control cybrid cells. The present study strongly indicates that the new mtDNA mutation at 14577 T/C is probably a major pathogenic mutation for type 2 diabetes in this family.

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