Mitochondrial DNA sequence variation in Finnish patients with matrilineal diabetes mellitus.
BACKGROUND
The genetic background of type 2 diabetes is complex involving contribution by both nuclear and mitochondrial genes. There is an excess of maternal inheritance in patients with type 2 diabetes and, furthermore, diabetes is a common symptom in patients with mutations in mitochondrial DNA (mtDNA). Polymorphisms in mtDNA have been reported to act as risk factors in several complex diseases.


RESULTS
We examined the nucleotide variation in complete mtDNA sequences of 64 Finnish patients with matrilineal diabetes. We used conformation sensitive gel electrophoresis and sequencing to detect sequence variation. We analysed the pathogenic potential of nonsynonymous variants detected in the sequences and examined the role of the m.16189 T>C variant. Controls consisted of non-diabetic subjects ascertained in the same population. The frequency of mtDNA haplogroup V was 3-fold higher in patients with diabetes. Patients harboured many nonsynonymous mtDNA substitutions that were predicted to be possibly or probably damaging. Furthermore, a novel m.13762 T>G in MTND5 leading to p.Ser476Ala and several rare mtDNA variants were found. Haplogroup H1b harbouring m.16189 T > C and m.3010 G > A was found to be more frequent in patients with diabetes than in controls.


CONCLUSIONS
Mildly deleterious nonsynonymous mtDNA variants and rare population-specific haplotypes constitute genetic risk factors for maternally inherited diabetes.
Institute of Clinical Medicine, Department of Neurology, University of Oulu, Oulu, Finland.
Heidi K
HK
Soini
Jukka S
JS
Moilanen
Saara
S
Finnila
Kari
K
Majamaa
D000328:Adult; D001483:Base Sequence; D016022:Case-Control Studies; D004272:DNA, Mitochondrial / Q000235:genetics*; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics*; D042967:Electron Transport Complex I / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005387:Finland; D020022:Genetic Predisposition to Disease; D006239:Haplotypes; D040941:Heredity; D006801:Humans; D008297:Male; D008875:Middle Aged; D024101:Mitochondrial Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D009035:Mothers; D010375:Pedigree; D011110:Polymorphism, Genetic; D018570:Risk Assessment; D012307:Risk Factors; D017422:Sequence Analysis, DNA; D055815:Young Adult
D004272:DNA, Mitochondrial; D024101:Mitochondrial Proteins; C481838:MT-ND5 protein, human; D042967:Electron Transport Complex I