eQTL Mapping allows to refine abdominal fatness QTL in chicken
Résumé
Whereas many QTL for various traits were mapped in livestock, the identification of causal mutations remains laborious. In this study, we propose to combine transcriptomic data and linkage analysis for refining a chicken QTL region previously detected on GGA5 with a strong effect on abdominal fatness. Transcriptome profiles for 46 offspring of a sire heterozygous for the QTL were obtained using a chicken 20K oligochips (ARK-genomics). Two groups among the 46 offspring were defined according to the phenotype. 113 genes among the 20460 oligo-genes were differentially expressed between these two groups on the basis of Anova analyses (p<1% at gene level). A principal component analysis (PCA) was then performed on the 46 offspring using these 113 genes as variables. The first axis of PCA separated clearly the two Q-q groups defined according to the QTL haplotype certainly received from their sire. These results confirmed that the QTL has a high effect on abdominal fatness. We then defined a new synthetic variable combining the expression levels of these 113 genes, weighted them by their coordinates of the PCA first axis. So we performed a linkage analysis on this variable with 10 markers along the GGA5 using the QTLMaP software. The results showed a trans e-QTL region for this synthetic expression variable which colocalized with the QTL region for fatness. These e-QTL region, which controls 113 genes differentially expressed between fat and lean progenies, gives new information about the function of the causal mutation responsible for fatness variability in chicken.