Genome-wide association study of post-weaning growth in rabbits
The aim of this work was to identify chromosomal regions and candidate genes associated with post-weaning growth in rabbits using a genome-wide association study. A total of 436 weaned rabbits from the Caldes line were distributed in two feeding regimes, 230 were fed ad libitum and 206 were restricted to 75% of ad libitum intake. Animal weight was recorded from 28 d to 56 d of age. Genotyping was performed using the Axiom rabbit array (Affymetrix) and after standard quality control a subset of 114604 annotated SNPs were retained for subsequent analysis. The maximum likelihood approach implemented in Qxpak 5.0 was used to test one snp at a time, separately for each trait; ADG on restricted (ADGr) or full feeding (ADGf). The model accounted for additive (polygenic) genetic effect, litter and cage effects, as well as the systematic effect of batch (5 levels). The R package q-value was used to adjust raw p-values to a False Discovery Rate of 0.05. While no significant associations were found at whole-genome level for any trait; a total of 55 significant trait-associated SNPs (TAS) distributed in Oryctolagus cuniculus Chromosomes (OCC) 3, 5 and 21 were declared to be associated with ADGf at chromosome-wise level. No associations were evidenced for ADGr at this level. In order to identify positional candidate genes related to ADGf, four genomic QTL intervals (OCC3:101-114 Mb, OCC5:8-10 Mb, OCC5:18-20 Mb and OCC21:6-9 Mb) were annotated using Biomart. Out of the 55 TAS, 27 (49%) were mapped in protein-coding genes. Remarkably, several genes related to growth such as ATXN2, ACAD10, TRAFD1, PTPN11, NDUFAF6 and FTO were mapped in these QTL regions. Polymorphism in the rabbit FTO gene has previously been reported to be associated with growth and meat quality traits. Further analysis will be performed to determine the role of these candidate genes for rabbit growth.