Gene Mutations from Older Fathers

An individual planning to put off parenting might want to consider this: a man’s sperm collects mutations at a rate of two per year.  While there may be perks to gaining some of those new mutations, others may be behind conditions like schizophrenia.

New sperm cells are continually created in the testes from a store of stem cells.  These stem cells multiply by making copies of their DNA, but mistakes can occur during this process, forming mutations. “These mutations are not necessarily deleterious,” says Anne Goriely at the University of Oxford. “They’re essential for a species to evolve.”

To find out how many mutations accumulate with age, Kári Stefánsson and his colleagues at Decode Genetics in Reykjavik, Iceland, sequenced the genomes of people with schizophrenia and autism, and compared them to the genomes of their parents, who did not have the conditions. Both conditions are thought to be linked to new mutations, says Goriely.

The approach allowed Stefánsson's team to tell in which parent the mutations that contribute to the conditions had originated.  They found that most new mutations were inherited from the father, and the number of them appeared to correlate with his age: about two new mutations occurred for every year older the father was when their child was conceived (Nature, DOI: 10.1038/nature11396).
The rate confirms what reproductive scientists predicted, says Goriely, who wasn't involved in the study.  But although parents-to-be should be advised on how their age may affect the health of their offspring, the finding doesn't mean that all older fathers risk passing on damaging mutations.  "Some mutations may be related to disease, but some may be beneficial, and some are likely to have no effect," says Goriely.

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