Thursday, August 23, 2012

Dads to Blame for Hereditary Problems

Excerpts from an article of interest about a study from researchers in Iceland linking the father's age to genetic disorders in his offspring:

"Kids' Mutation Rate Tracks with Father's Age," By Michael Smith, North American Correspondent, MedPage Today Published: August 22, 2012 Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston

 In a large-scale genetic study, every 1-year increase in the father's age at conception of a child added two new single nucleotide polymorphisms, according to Kari Stefansson, MD, PhD, of deCODE Genetics in Reykjavik, Iceland, and colleagues.

 In contrast, the mother's age was not significantly associated with an increased number of such genetic variants, Stefansson and colleagues reported in the Aug. 23 issue of Nature.

"A father's age at the time a child is conceived explains nearly all of the population diversity in new hereditary mutations found in the offspring," Stefansson said in a statement. "Conventional wisdom has been to blame developmental disorders of children on the age of mothers," he said, but "it is the age of fathers that appears to be the real culprit."

The likelihood of new mutations in sperm is higher than in eggs, because sperm are continually produced, so there is more opportunity for genetic errors to creep in.

 One implication of the findings is that demographic changes that lead to men fathering children at an older age "can have a considerable impact on the rate of certain diseases linked to new mutation," Stefansson said.

The paternal effect on mutation rate has been demonstrated before, commented Alexey Kondrashov, PhD, of the University of Michigan in Ann Arbor. But the Icelandic study yields "the most precise and definite" estimates so far, he wrote in an accompanying article.

One implication of the finding, he argued, is that the rise of such syndromes as autism spectrum disorder might be partly explained by a relative lack of evolutionary selection pressure on humans, combined with the paternal effect.

The study was supported by the National Institutes of Health and the European Community. Stefansson is CEO of deCODE Genetics, and most authors are employees of the company.

Story at a glance: A mother-father-offspring study from Iceland found that de novo mutations in the offspring correlated with older age for the father.

Two extra single nucleotide polymorphisms occurred per year for every year of age older the father was at conception.

It's the father's age – not the mother's – that increases the risk of new hereditary mutations in children, researchers reported.