The babies of teen fathers have surprisingly high levels of DNA mutations, which may help explain why the children of adolescent dads have a higher risk for disorders such as autism, schizophrenia, and spina bifida, according to a new study by the University of Cambridge.
The initial findings of the genetic study of over 24,000 parents and their children suggest that sperm cells in male teens have approximately 30 percent higher rates of DNA mutation than those of young men in their 20s, and that teenage boys have similar levels of DNA mutation in their sperm cells to men in their late thirties and forties.
By puberty, male germ cells go through around 150 cell divisions, compared to the 22 cell divisions experienced by female oocytes (immature egg cells). This increases the odds of DNA mutation by cell division in the germ cells of teenage boys, and therefore brings with it a higher risk of hereditary disease in the children of teen dads.
It was previously assumed that germ cells (cells that create sperm or eggs) in both boys and girls go through a similar number of cell divisions, and should have roughly the same rates of DNA mutation by the time an individual reaches puberty.
The new study, however, has found that the number of cell divisions — and consequently DNA mutation rates — in the germ cells of teenage boys is six times higher than for those of girls, and that DNA mutations passed down to the babies of teen fathers are higher as a result.
“It appears that the male germ cells accumulate DNA errors unnoticed during childhood, or commit DNA errors at an especially high level at the onset of puberty. However, the reason for this is not yet clear,” said geneticist Dr. Peter Forster, a Fellow of Murray Edwards College and the McDonald Institute at the University of Cambridge, who conducted the study with researchers from the Institute of Forensic Genetics in Münster, Germany.
“Possibly the DNA copying mechanism is particularly error-prone at the beginning of male puberty. Or, sperm production in boys may undergo dozens more cell cycles — and therefore DNA copying errors — than has previously been suspected,” he said.
The new findings refute former ideas that the younger the man, the less cell division and the less risk of DNA mutations in germ cells. The textbooks may well need to be rewritten as a result of the new findings, said Forster.
The study is published in the journal Proceedings of the Royal Society B.
Source: University of Cambridge