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Second X Helping

Having two X chromosomes may contribute to women's longer lifespans, Discover's D-brief blog reports.

Women outlive men by an average four years and while lifestyle influences have thought to play a role, researchers from the University of California, San Francisco, also suspected there might be a genetic role, it adds. The researchers used a mouse model in which they generated XX mice with ovaries, XX mice with testes, XY mice, with ovaries, and XY mice with testes by manipulating their SRY gene. As they report in Aging Cell, the researchers found that XX mice with ovaries lived longer than XY mice with ovaries, but no difference in mortality between XX mice with testes and XY mice with testes.

"This suggests that the hormones produced by female gonads increase lifespan in mice with two X chromosomes, either by influencing how the mouse develops or by activating certain biological pathways during their lives," senior author Dena Dubal from UCSF tells D-brief.

She and her colleagues note in their paper, though, that whether the effect is due to the presence of a second X chromosome or the lack of a Y chromosome still needs to be teased out.