A Link between Mitochondrial DNA Haplogroup and Ischemia

diseases collectively known as mitochondrial disease and including multisystem disorders. Mitochondrial DNA (mtDNA) mutations also manifest in disturbing the reactive oxygen species balance in the cell, leading to diverse pathological conditions. The maternally inherited mtDNA does not undergo biparental recombination but accumulating polymorphisms have been forming branches of the phylogenetic tree throughout human history. mtDNA polymorphism is far more robust in terms of its discerning power than nuclear SNPs. These so-called mtDNA haplogroups represent major subdivisions of phylogeny, which diversified as a function of geographic migrations of humans, thousands of years ago, creating region-specific haplogroup variations. Mitochondria, almost exclusively maternally inherited, have been the subject of investigation for diseases that have a sex bias. It is known that women have a greater chance of inheriting a stroke than men, consistent with the maternally transmitted risk allele [5] . An earlier report documented the role of pathogenic mtDNA mutations in a maternally inherited disease causing stroke-like symptoms, MELAS (mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes), wherein the cerebral vasculature showed biochemical and structural abnormalities [6] . Other reports found an association between mtDNA genetic variation and risk factors for ischGenomic medicine or gene-based medicine, terms coined to describe a paradigm shift in human health, as a consequence of the Human Genome Project [1] , is under retrospection to assess the true impact of this genome revolution [2] . The tangible gains of genomic medicine have resulted in a better understanding of the molecular pathways leading to disease manifestations and the importance of genes and specific mutations therein in terms of drug response and disease progression and in assessing the risk of contracting disease. Individual genetic ancestry has been found to improve predictions of pulmonary function in self-identified African Americans [3] pointing to the significance of ‘race correction’ in pulmonary function testing [4] . These genetic markers are the prime gain of the genomic revolution, even though questions of accuracy of such predictions remain. While single-nucleotide polymorphisms (SNPs) in the nuclear genome continue to be the focus of disease association, enough reports highlight the importance of nonnuclear SNPs, the epigenetic phenomenon and the environment as risk factors. The mitochondrial respiratory chain, the most fundamental and key process for cellular energy, is vital for normal functioning of an organism. Any disruption caused by mutations in the genes encoding critical enzymes in the respiratory pathway, present in the mitochondrial or nuclear genome, has a major impact on a diverse group of Received: August 19, 2010 Accepted: October 4, 2010