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Parental Genotypes Can Influence Children's Phenotypes Through 'Genetic Nurture'

NEW YORK (GenomeWeb) – Children can be affected by alleles their parents have, even if they do not inherit those alleles themselves, a new study suggests.

Scientists have long argued about how nature and nurture influence who people are. But, a Decode Genetics-led team of researchers has found that genes can also influence the environment. The researchers reported in Science today that alleles that a child's parents have could affect that child by influencing environment the parents provide.

The Decode team used data from a meta-analysis encompassing more than 21,000 individuals in which the proband and at least one parent was genotyped to estimate the influence of untransmitted alleles on educational attainment. The untransmitted alleles, they found, had about 30 percent of the effect that the transmitted ones did. They dubbed this genetic influence on the environment "genetic nurture."

"The discussion of nature (genes) versus nurture is often framed so that the two factors are treated as, if not competitive, independent forces," first author Augustine Kong from Decode said in a statement. "This study illustrates that not only do genes and nurture often work hand in hand, there is a genetic basis to nurture."

Kong and his colleagues turned to a cohort of 21,637 Icelanders born between 1940 and 1983 for whom educational attainment data was available and who had undergone genotyping, as had at least one of their parents. Based on 618,762 SNPs, the researchers developed polygenic scores for transmitted paternal alleles, transmitted maternal alleles, untransmitted paternal alleles, and untransmitted maternal alleles.

Using these scores, the researchers gauged the effect of these alleles on educational attainment to find that the untransmitted alleles had 29.9 percent of the effect that transmitted ones did.

"This genetic nurture effect is an indirect link between parental genotypes and children's characteristics, not caused by the children's own biology but rather by the family environment that covaries with parental genes," noted Vrije Universiteit's Philipp Koellinger and Paige Harden from the University of Texas in a related commentary in Science.

Kong and his colleagues further reported that this finding wasn't limited to educational attainment, but could also been seen among other traits like the age at which individuals have their first child and cigarette smoking.

For some traits, though, Kong and his colleagues noted that the effect varied by whether the maternal or paternal genotype was considered. They found that while maternal and paternal polygenic scores had similar effects on educational attainment, maternal scores had greater effects on nutrition and health-related traits.

The researchers also found that sibling genotypes could also make their mark on the proband.

"Despite the treasure trove of gene discoveries made though non-family-based association studies in the last decade or so, the results here are a reminder that, without family data, the story can often be, if not distorted, incomplete," author Kari Stefansson, CEO of Decode, said in a statement.

GWAS results, the researchers pointed out in their paper, have been assumed to encompass solely direct effects, but may in fact also reflect genetic nurturing.

Koellinger and Harden added in their commentary that genetic associations could depend on the environmental context. "[This study] reminds us yet again of the methodological problems that plague scientists as we try to understand individual differences in complex human behaviors and diseases — but also illustrates how understanding nature can provide us with new tools for studying nurture," they wrote.