Reduced variance of gene expression at numerous loci in a population of chickens selected for high feather pecking

Changes in gene expression in response to selection were studied by comparing microarray expression profiles among a population of domestic chickens selected for high feather pecking (FP) with a control population and a population selected for low FP. No transcripts showed significant differences among populations with respect to mean expression scores, but numerous transcripts showed reduced variance in expression scores in the high FP population in comparison to control and low FP populations. The reduction in variance in the high FP population generally involved transcripts whose expression scores had a negatively skewed distribution in the control population but not in the high FP population. A certain number of these transcripts corresponded to genes whose expression was significantly associated with either severe FP (SFP) or gentle FP. The patterns of gene expression associated with SFP and gentle FP were distinct, suggesting that very distinct underlying neural mechanisms underlie these 2 behaviors, with SFP showing more signs of an association with synaptic plasticity and with an immunosuppressive stress response.