Social Interactions and Indirect Genetic Effects on Complex Juvenile and Adult Traits

Abstract

Most animal species are social in one form or another, yet many studies in rodent model systems use either individually housed animals or ignore potential confounds caused by group housing. While such social interaction effects on developmental and behavioral traits are well established, the genetic basis of social interactions has not been researched in as much detail. Specifically, the effects of genetic variation in social partners on the phenotype of a focal individual have mostly been studied at the phenotypic level. Such indirect genetic effects (IGEs), where the genotype of one individual influences the phenotype of a second individual, can have important evolutionary and medically relevant consequences. In this chapter, we give a brief outline of social interaction effects, and how systems genetics approaches using recombinant inbred populations can be used to investigate indirect genetic effects specifically, including maternal genetic effects. We discuss experimental designs for the study of IGEs and show how indirect genetic loci can be identified that underlie social interaction effects, their mechanisms, and consequences for trait variation in focal individuals.

Born to Cry: A Genetic Dissection of Infant Vocalization

“…The BXDs are particularly useful for developmental analyses of behavior because each strain and genome can be studied at many time points and using nearly isogenic sets of males and females. This makes it highly practical to study gene-by-environment interactions, sex differences, and indirect genetic effects (IGEs; Ashbrook et al, 2015a , 2017 ; Ashbrook and Hager, 2017 ; Baud et al, 2017 ). We have previously shown that IGEs of the offspring genome influence maternal behavior ( Ashbrook et al, 2015a , 2017 ; Ashbrook and Hager, 2017 ), and differences in infant vocalizations may be a key factor controlling parental care.…”

Disentangling Social-Genetic From Rearing-Environment Effects for Alcohol Use Disorder Using Swedish National Data

“…The possibility that a spouse’s genotype could influence a partner’s drinking behavior is consistent with emerging findings from a growing literature on social genomics (Baud et al, 2017; Domingue & Belsky, 2017) that demonstrate associations between a social partner’s genotype and another’s outcomes. Although the field of social genomics is relatively new, the concept of social-genetic effects has a long history in evolutionary and human genetics (Ashbrook & Hager, 2017; Wolf et al, 1998) and is related to the idea that genes influence phenotypes beyond the body as part of what Dawkins (1982) termed “the extended phenotype.” Historically, social-genetic effects have been studied in the context of biologically related individuals, such as the effect of maternal genotype on offspring outcomes such as crown-heel length at birth.…”

Post‐genomic behavioral genetics: From revolution to routine

“…Social genetic effects are not just important for understanding the behavioral phenotype of an individual, but also for the evolution of behaviors, as they represent an environment which is composed of the genotype of interacting individuals: therefore it is an environment that can respond to selection (Moore et al 1997, 2002; Wolf & Brodie 1998; Bijma & Wade 2008; McGlothlin et al 2010). Indeed, some behaviors cannot exist without social interactions, for example courtship (Whitney et al 1973; Doty 1974; Petfield et al 2005; Neunuebel et al 2015), play (Cox & Rissman 2011; Lukas & Wöhr 2015), aggression (Wilson et al 2009; Anholt & Mackay 2012; Camerlink et al 2013) and parental care (Kölliker et al 2000; Kölliker & Richner 2001; Hunt & Simmons 2002; Smiseth et al 2012; Ashbrook & Hager 2017). Some of the earliest social genetic effects identified were maternal genetic effects (MGE), and these were studied extensively in livestock (Dickerson 1947; Willham 1963, 1972; Cundiff 1972; Hanrahan 1976; Ellen et al 2014), although some work was carried out in rodents (Hanrahan & Eisen 1973).…”

“…Eleven out of 50 recorded phenotypes showed social genetic effects, and there was an interaction between the genotype of the target individual and the interacting individual. Ashbrook et al (2015a, 2017; Ashbrook & Hager 2017) have begun to map social genetic effect QTL for a number of interactions between mothers, offspring and siblings. To do this, cross-fostering was used: for social genetic effects on maternal behavior, the genotype of the mother was kept constant between all litters, whereas the genotype of the offspring was differed (different lines of the BXD population).…”

“…We will give a few examples of how the social genetic effect studies above could be extended to a whole genome level. We have previously shown that cross-fostering can be used to investigate maternal, offspring and sibling effects during early life (Ashbrook et al 2015a): the technique is described in depth in Ashbrook & Hager (2017) and this could be extended into later life phenotypes, or, for example, transcriptome mapping. It has been clearly demonstrated that differences in maternal care can influence offspring behavior and gene expression during adult life (e.g.…”