Feb. 12, 2004 -- Your parents may largely dictate how long you're going to live. And your mom appears to have most of the control over your "aging gene."
Previous research has linked the length of telomeres -- the tips of chromosomes -- to disease and life span, say researchers. These structures become progressively shorter each time the cell divides, and it is thought that this shortening is one of the critical features of cellular aging and illness. One study showed people with heart disease had shorter telomeres, while other research showed telomere length was a predictor of death.
And while twin studies have indicated that telomere length -- and possibly life span -- is inherited, it's unclear how this is passed from one generation to the next.
So researcher Jan A. Staessen and colleagues sought to determine just where this aging gene might come from. The study is presented in this week's issue of The Lancet. In it they examined DNA from more than 300 parents and offspring of multigenerational families.
They found that sex, age, and smoking were all significant predictors of telomere length. Men have shorter telomeres -- makes sense given their shorter life spans. In addition, telomere length was shorter among smokers. As expected, older people had shorter telomeres.
Moms Hold Most of the Power
But it turns out that dads may not have as much say when it comes to telomere length -- especially when it comes to their sons.
The researchers found a much stronger correlation between the mothers' telomere length and that of the offspring. Dads' telomere length was somewhat predictive of their daughters' life spans.
And since women have two X chromosomes, which are generally longer than those found in men, and men have just one -- to go along with their Y chromosome -- the researchers conclude that this aging gene most likely lives on the X chromosome. This would explain why a mother's telomere length is more predictive of life span.
To help support this idea, the researchers point to a condition called dyskeratosis congenita, which is due to a mutation on the X chromosome. People with this condition have unstable telomeres and develop diseases at an early age that are normally associated with aging. In addition, they generally suffer premature death.
As to why men -- and smokers -- have shorter telomeres, the researchers suggest that it may be due to a decreased ability to handle damaging by-products in the body. They say that women produce fewer of these "reactive oxygen species" and might be able to metabolize them better. And likewise, the shorter telomere lengths seen in smokers may result from higher amounts of these by-products.
Though further research is needed, Staessen says that the process of aging -- and life span -- may be determined by your mother's X chromosome.