Everyone knows that as men age so do their sperm, slowing a little and becoming less... potent. But research suggests that sperm actually mutate with age—which in turn could increase the chances of fathering a child with a genetic disorder.
New Scientist reports on research by Anne Goriely from the University of Oxford, writing that "like a slow form of cancer, these mutations cause stem cells in the testicles to divide abnormally, resulting in an increasing proportion of mutant sperm as men age and an ever growing chance of a mutant sperm fertilising an egg."
Recently, some of these mutations have been tied to rare conditions, such as Apert syndrome, where childhood development falters resulting in things like fused toes and fingers. But it's also believed that the mutations could give rise to far more common disorders like autism and schizophrenia, too—and could in fact help explain why those conditions seem increasingly common.
Perhaps most concerning is that the researcher believe a "selfish sperm" effect could make these problems spread:
What if some mutations give the stem cells a selective advantage by making them divide abnormally and produce more than one daughter spermatogonium each? One such "selfish spermatogonium" arising in the testicles of a young man could give rise to thousands of these mutant stem cells after a decade or two, each carrying a copy of the mutated gene. The proportion of mutant sperm would increase at an exponential rate, rather than linearly.
Indeed, that effect has been spotted in some small studies—but only with conditions definitely tied to mutated sperm. In turn, that should be less of a concern because those conditions usually prevent people having children, so the faulty genes are stopped from spreading. In the meantime, we don't yet know if more common conditions acre actually spread by the selfish sperm effect or not.
So, more work's required. But what we do know is that younger sperm seem to be healthier sperm—so, folks, you know what needs to happen. [New Scientist]
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