The Affymetrix GeneChip Mouse Gene 2.0 ST Array (Thermo Fisher) was used according to the manufacturer’s instructions. A Custom CDF V. 22 with ENTREZ-based gene definitions was used to annotate the arrays.23 (link) The raw fluorescence intensity values were normalized by applying quantile normalization and robust multiarray analysis background correction. A batch normalization was used to remove the individual mouse variations. An analysis of variance was performed to identify differentially expressed genes using the commercial software package SAS JMP Genomics, V. 7 (SAS Institute). A false positive rate of a=0.05 with false discovery rate correction was taken as the level of significance. Gene set enrichment analysis was used to determine whether defined lists (or sets) of genes exhibit a statistically significant bias in their distribution within a ranked gene list.24 (link) Pathways belonging to different cell functions were obtained from public external databases (KEGG, http://www.genome.jp/kegg).