Missing genes not always a problem for people

Many genes may be dispensable.

Each of 3,222 British people with Pakistani heritage carries, on average, mutations in 140 genes that stop those genes from working, researchers report online March 3 in Science. Examination of those people’s exomes, the small portion of the genome that encodes proteins, revealed that among a subset of 821 participants, a total of 781 genes were rendered obsolete by “loss-of-function” mutations. Those genes include 422 that scientists didn’t know people could live without and still be healthy.

Previous studies had indicated that some genes are commonly missing in healthy people. The new study suggests that even rare mutations that disable both copies of a gene, which scientists thought would be associated with diseases, aren’t necessarily a problem.

Researchers in England and the United States compared health records of 638 people in the study who have rare mutations that abolish both copies of one or more genes with records from 1,524 people without the rare mutations. Those with rare mutations were no more likely to have health issues than those without, the researchers found.

Even really important genes may go missing with no harm. One woman had mutations in the PRDM9 gene, which is important during the formation of eggs and sperm. Without the mouse version of the gene, mice are sterile. Dogs have a fallback mechanism to compensate for losing the gene. The woman had a child, indicating that she is fertile, so humans must have a way to compensate for the missing gene, too — though it appears to be different than dogs’.

Compensatory mechanisms could complicate the search for genes responsible for rare genetic diseases, the researchers say.