In most areas of the world, women tend to outlive men. A new study conducted at the University of California, San Francisco has come up with a genetic explanation for the gap in life expectancy.
The X chromosome contains many genes related to the brain and is essential to human survival. The Y chromosome, present only in males, is not essential to survival.
Researchers used genetics to produce four combinations of chromosomes and sexual organs in mice: XX with ovaries and XY with testes – the typical combinations founded and nature. The other two were genetically altered mice – XX with testes and XY with ovaries. The two combinations with XX chromosomes lived longer with the XX combination with ovaries living the longest.
“We’ve long wondered what causes female longevity,” said Dena Dubal an associate professor of neurology at UCSF and senior author of the study. “One can imagine nature has driven females to evolve this way. When you’re living longer, you can really ensure the well-being of your offspring, and maybe even their offspring.”
A neurologist and neuroscientist who specializes in healthy aging, Dr. Dubal is actively investigating how the X and Y chromosomes exert such far-reaching influences. “We don’t yet understand how the second X chromosome decreases mortality in aging,” she said. “When things go wrong in aging, having more of the X chromosome, along with its diversity of expression, could be really beneficial.”
The full study, “Female XX Sex Chromosomes Increase Survival and Extend Lifespan in Aging Mice,” was published on the website of the journal Aging Cell. It may be accessed here.