Brain gene expression in relation to fearfulness in female red junglefowl (Gallus gallus)

The biology of fear is central to animal welfare and has been a major target for selection during domestication. Fear responses were studied in female red junglefowl (RJF), the ancestor of domesticated chickens. A total of 31 females were tested in a ground predator test, an aerial predator test and a tonic immobility (TI) test, in order to assess their level of fearfulness across different situations. Two to six variables from each test were entered into a principal component (PC) analysis, which showed one major fearfulness component (explaining 27% of the variance). Based on the PC scores, four high- and four low-fearful birds were then selected for gene expression analysis. From each of these birds, the midbrain region (including thalamus, hypothalamus, pituitary, mesencephalon, pons, nucleus tractus solitarii and medulla oblongata), was collected and global gene expression compared between groups using a 14k chicken cDNA microarray. There were 13 significantly differentially expressed (DE) genes (based on M > 1 and B > 0; FDR-adjusted P < 0.05) between the fearful and non-fearful females. Among the DE genes, we identified the neuroprotein Axin1, two potential DNA/RNA regulating proteins and a retrotransposon transcript situated in a well-studied quantitative trait loci (QTL) region on chromosome 1, known to affect several domestication-related traits. The differentially expressed genes may be part of a possible molecular mechanism controlling fear responses in fowl.