mtDNA haplogroups and disease

Three recent studies:

Differences in mtDNA haplogroup distribution among 3 Jewish populations alter susceptibility to T2DM complications. BMC Genomics. 2008 Apr 29;9(1):198 [Epub ahead of print]

Our results identified population-specific susceptibility factors of which the best example is the Ashkenazi Jewish specific haplogroup N1b1, having an apparent protective effect against [type 2 diabetes mellitus] complications in Ash (p=0.006), being absent in the NAF population and under-represented in the Seph population. We have generated and analyzed whole mtDNA sequences from the disease associated haplogroups revealing mutations in highly conserved positions that are good candidates to explain the phenotypic effect of these genetic backgrounds.

New evidence of a mitochondrial genetic background paradox: impact of the J haplogroup on the A3243G mutation. BMC Med Genet. 2008 May 7;9(1):41 [Epub ahead of print]

BACKGROUND: The A3243G mutation in the tRNALeu gene (UUR), is one of the most common pathogenic mitochondrial DNA (mtDNA) mutations in France, and is associated with highly variable and heterogeneous disease phenotypes. To define the relationships between the A3243G mutation and mtDNA backgrounds, we determined the haplogroup affiliation of 142 unrelated French patients a diagnosed as carriers of the A3243G mutation a by control-region sequencing and RFLP survey of their mtDNAs. RESULTS: The analysis revealed 111 different haplotypes encompassing all European haplogroups, indicating that the 3243 site might be a mutational hot spot. However, contrary to previous findings, we observed a statistically significant underepresentation of the A3243G mutation on haplogroup J in patients (p=0.01, OR= 0.26, C.I. 95%: 0.08-0.83), suggesting that might be due to a strong negative selection at the embryo or germ line stages. CONCLUSION: Thus, our study supports the existence of mutational hotspot on mtDNA and a "haplogroup J paradox", a haplogroup that may increase the expression of mtDNA pathogenic mutations, but also be beneficial in certain environmental contexts.

Mitochondrial Haplogroups. Ischemic Cardiovascular Disease, Other Diseases, Mortality, and Longevity in the General Population. Circulation. 2008 May 5 [Epub ahead of print]

BACKGROUND: -Rare mutations in the mitochondrial genome may cause disease. Mitochondrial haplogroups defined by common polymorphisms have been associated with risk of disease and longevity. We tested the hypothesis that common haplogroups predict risk of ischemic cardiovascular disease, morbidity from other causes, mortality, and longevity in a general population of European descent. Methods and Results-We followed 9254 individuals from the Danish general population, in the Copenhagen City Heart Study, prospectively for risk of ischemic cardiovascular disease, morbidity from other causes, and mortality during 25 and 11 years, respectively. Haplogroup frequencies were as follows: H (45.9%), U (15.9%), T (9.9%), J (9.1), K (6.2%), V (4.5%), W/I (3.8%), and Z (3.5%). Hazard ratios for hospitalization due to all cardiovascular disorders (haplogroup U: 1.0 [95% confidence interval{CI}, 0.9 to 1.1]; T: 0.9 [95% CI, 0.8 to 1.0]; J: 1.0 [95% CI, 0.9 to 1.1]; K: 1.0 [95% CI, 0.9 to 1.2]; V: 1.0 [95% CI, 0.9 to 1.2]; W/I: 0.8 [95% CI, 0.7 to 1.0]; Z: 1.0 [95% CI, 0.8 to 1.2]), ischemic heart disease (U: 0.9 [95% CI, 0.8 to 1.1]; T: 0.9 [95% CI, 0.7 to 1.0]; J: 1.1 [95% CI, 0.9 to 1.2]; K: 1.1 [95% CI, 0.9 to 1.3]; V: 1.1 [95% CI, 0.9 to 1.4]; W/I: 1.1 [95% CI, 0.8 to 1.4]; Z: 1.1 [95% CI, 0.8 to 1.4]), and ischemic cerebrovascular disease (U: 1.1 [95% CI, 0.9 to 1.4]; T: 0.9 [95% CI, 0.7 to 1.2]; J: 1.1 [95% CI, 0.9 to 1.4]; K: 1.0 [95% CI, 0.8 to 1.4]; V: 1.1 [95% CI, 0.8 to 1.5]; W/I: 0.8 [95% CI, 0.5 to 1.3]; Z: 0.9 [95% CI, 0.6 to 1.4]) did not differ from 1.0 for any haplogroup versus the most common haplogroup H. Results were similar for hospitalization due to infectious and parasitic diseases, respiratory infections, respiratory disorders, malignant neoplasms, digestive disorders, musculoskeletal disorders, neuropsychiatric disorders, and miscarriages. Likewise, hazard ratios for death from all causes were not different from 1.0 for any haplogroup versus haplogroup H (U: 1.0 [95% CI, 0.8 to 1.1]; T: 0.9 [95% CI, 0.8 to 1.1]; J: 0.9 [95% CI, 0.8 to 1.1]; K: 1.0 [95% CI, 0.8 to 1.2]; V: 1.1 [95% CI, 0.9 to 1.3]; W/I: 0.8 [95% CI, 0.7 to 1.1]; Z: 0.9 [95% CI, 0.7 to 1.2]). Finally, after stratification by major causes of death, hazard ratios remained insignificant. Conclusions-Our results do not support an association of mitochondrial haplogroups with risk of ischemic cardiovascular disease, morbidity from other causes, mortality, or longevity in a large general population of European descent.