Everyone knows that friends and family influence your health and behavior to some degree. The question is how much? Researchers at the Wellcome Genome Campus have taken a genetics-based approach to find out. Their study reveals the important effect social environment has on phenotypic characteristics in a population.
Assessment of the impact of social environment on one’s health can be broad and biased, depending on how it is examined. If a person gets the flu, it is likely that their friend might get it as well. However, what impact, if any, would one person’s growth rate or anxiety level have on another person’s genetics? Previous attempts to look into the depth of affect from social influence relied on prior knowledge of the mechanism mediating the social effect in question. For example, one person’s smoking addiction can influence another to pick up the habit. However, most phenotypes do not have a known direct mechanism of interaction with the surrounding environment. By investigating phenotypic traits with genotypic data, new associations and underlying mechanisms could be brought to light.
Researchers studied the social genetic effects, or indirect genetic effects, in mice by testing behaviors and measuring physiological traits of cage mates. Social genetic effects (SGE) are the association between the genotype of one individual and the phenotype of another. SGEs can be seen as the genetic basis for social contributions to health and behavior and can be studied without prior knowledge of any connection to specific phenotypes.
The team, led by Oliver Stegle of the European Bioinformatics Institute, used social genetic effects as an approach to quantifying any impact of one’s social environment on genetics. They measured more than 100 phenotypes against genome-wide gene expression analysis in a population of inbred mice and again for confirmation in a separate population of outbred mice. The phenotypes tested included anxiety levels, helplessness, body weight, wound healing, and immune functions. The study was recently published in PLOS Genetics.
The findings suggested that the genetic variation in mice sharing the same cages does indeed contribute to variation in behavioral and biological phenotypes. Social genetic effects influenced 29% of phenotypic variance in the mice. In some cases, the contribution of these traits exceeded any contribution from direct genetic effects, or effects of one’s genotype on its own phenotype, which comes from familial genetics.
The group concluded that social genetic effects can have a profound influence over phenotypic variation within a close population. The results can be applied to direct genetic studies to help remove any unknown bias. Not including analysis of social genetic effects in a study could change estimates of direct heritability of traits.