Abstract
Despite high estimates of the heritability of aggressiveness, the genetic basis for individual differences in aggression remains unclear. Previously, we showed that the wild-derived mouse strain MSM/Ms (MSM) exhibits highly aggressive behaviors, and identified chromosome 15 (Chr 15) as the location of one of the genetic factors behind this escalated aggression by using a panel of consomic strains of MSM in a C57BL/6J (B6) background. To understand the genetic effect of Chr 15 derived from MSM in detail, this study examined the aggressive behavior of a Chr 15 consomic strain towards different types of opponent. Our results showed that both resident and intruder animals had to have the same MSM Chr 15 genotype in order for attack bites to increase and attack latency to be reduced, whereas there was an intruder effect of MSM Chr 15 on tail rattle behavior. To narrow down the region that contains the genetic loci involved in the aggression-eliciting effects on Chr 15, we established a panel of subconsomic strains of MSM Chr 15. Analysis of these strains suggested the existence of multiple genes that enhance and suppress aggressive behavior on Chr 15, and these loci interact in a complex way. Regression analysis successfully identified four genetic loci on Chr 15 that influence attack latency, and one genetic locus that partially elicits aggressive behaviors was narrowed down to a 4.1-Mbp region (from 68.40 Mb to 72.50 Mb) on Chr 15.
Highlights
There are large individual differences in aggression, a trait that is widely conserved within the animal kingdom
We focused on MSM chromosome 15 (Chr 15), which is associated with a reduction in the threshold at which aggressive behavior is initiated
We reported that the Behavior of C57BL/6J (B6)-Chr15MSM consomic strain showed a longer duration of tail rattles and a higher proportion of animals that initiated aggressive behavior, but the frequencies of attack bites and pursuits were similar to those in the B6 strain, when we used the B6 strain as an intruder [9]
Summary
There are large individual differences in aggression, a trait that is widely conserved within the animal kingdom. Studies using gene-modification techniques have revealed more than 50 genes that are involved in aggressive behavior in mice (for review see [3,4,5]). In natural populations, the extent to which each gene/genetic locus can contribute to individual differences in aggression remains unknown. Aggressive behavior itself has a complex nature as a social behavior in which the behavior of a test animal receives strong feedback from the behavior of other animals that it encounters [6,7]. When we study the genetic basis of aggressive behavior, it is always important to consider which aspect of such behavior is modulated by the genetic factor(s) in question
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