Trouble in the Cell’s Power Plant
Aging diseases link to a mitochondria gene
Context: If you have high blood pressure, you’re more likely to be obese and to have high cholesterol and a host of other unhealthy conditions. Recent evidence suggests that obesity keeps the body’s cells from responding properly to blood sugar, leading to diabetes. However, why these conditions are associated with high blood pressure is still poorly understood. A team of researchers from Yale University and the State University of New York Upstate Medical University sought an answer in genetics and found one in mitochondria. Most cells contain hundreds of mitochondria, rod-shaped structures that originated billions of years ago when a cell engulfed a bacterium but did not destroy it. Now, the bacterium’s descendants help the body’s cells convert food into energy.
Methods and Results: Frederick Wilson of Yale and his colleagues studied a family with a high incidence of conditions associated with hypertension and tracked inheritance in 142 blood relatives over four generations. After adjusting for differences in age, weight, and medication use, the researchers found a clear pattern of inheritance. All the conditions descended through the maternal line, indicating that the culprit gene was mitochondrial. (A person’s mitochondria derive from those originally present in the ovum and have their own, bacterialike DNA.) A full sequence of affected family members’ mitochondrial genome revealed 14 differences from standard sequences. Thirteen had been previously reported to have no impact. The 14th was new and was mapped to a gene for a transfer RNA, a molecule essential to building proteins. In fact, the gene is constant across animals, fungi, plants, and even bacteria.
Why it Matters: Against a noisy backdrop of studies showing how heart disease, depression, and other complex diseases can be attributed to small effects from many genes, Wilson and his colleagues’ research shows that a single gene can be tied to many disease-associated conditions. More importantly, the research pins responsibility for several diseases on mitochondria, whose function declines with age. Those seeking the fountain of youth, or just hoping to stave off the ravages of old age, may benefit from further studies of these vestiges of ancient bacteria.
Source: Wilson, F. H. et al. 2004. A cluster of metabolic defects caused by mutation in a mitochondrial tRNA. Science 306: 1190-1194.