Sperm from older men have more genetic mutations

Human semen does not Gene mutations only accumulate with age; As a ratio Sperm The likelihood of dangerous mutations increases, as does the risk of disease in offspring.

This is according to a new study conducted by researchers at the Sanger Institute and King’s College London. The team sequenced semen samples from individuals between the ages of 24 and 75, using high-resolution techniques, and found that the male germ line (the line of cells that produce sperm) undergoes a combination of mutation and positive selection.

The scientists used a paired-end sequencing technology called NanoSeq, which can detect rare mutations with a very low margin of error. This allowed them to analyze 81 sperm samples from 57 donors. The results showed that a man’s sperm adds an average of 1.67 new mutations every year.

But the most striking aspect of the study is not just the accumulation of mutations with age. Researchers have discovered that the male germ line is subject to positive selection. That is, certain mutations provide an advantage to the cells that produce sperm and expand. They identified that many of these mutations are found in genes associated with developmental disorders or predisposition to childhood cancer.

“We expected to find evidence that selection affects mutations in sperm,” said Matthew Neville, co-author of the published study. This month In the journal Nature. “What surprised us was the extent to which the number of sperm carrying mutations associated with serious diseases increased.”

What does this mean for children of older parents?

Researchers estimated that about 3 to 5 percent of sperm in middle-aged and older men carry some disease-causing mutation in the exome (the coding part of the genome). This represents a higher risk than previous estimates. In more specific numbers, the estimated proportion for men in their 30s was close to 2 percent, while it was about 4.5 percent for men in their 70s.

From an evolutionary and clinical perspective, the implications are significant. Evolutionarily speaking, it appears that the male germ line is not simply a ‘machine’ that accumulates errors: there is a dynamic process of mutation and selection that can modify the genetic ‘quality’ of sperm with the age of the father.

However, on the clinical side, it raises questions about reproductive planning, genetic counseling, and the additional risks associated with an older father. The authors argue that although the percentages are still modest, the accumulation is not only linear but also has an element of selection that favors mutations with the potential to spread.