Affymetrix GeneChip Whole Transcript Sense Target Labeling Assay Manual Version 4 was followed for generation and amplification of biotinylaed sensestrand DNA targets. Briefly, 300 ng total RNA underwent firststrand and second strand cDNA synthesis. Complementary RNA was generated and used to produce sense-strand cDNA, which was fragmented and end-labeled with biotin. Microarrays were hybridized, washed, stained, and scanned according to the protocol described in the WT sense target labeling assay manual from Affymetrix . Microarray data were normalized using RMA . Probes were mapped to Entrez Gene identifiers using BioMart . Genes were defined as differentially expressed if the ratio between the MLN4924 average expression in three mutant and the three WT mice was at least 1.2 and t-test p-value was below 0.05. For visualization purposes , the expression pattern of each gene was normalized to mean = 0 and standard deviation =1. All original data files from the microarray experiments have been deposited in the National Center for Biotechnology Information Gene Expression Omnibus . File S1 contains all the differentially expressed genes . All data is MIAME compliant. The MAPK signaling cascade is involved in various cellular processes and is well conserved in evolution . In the vertebrate MAPK family, 13 members have been previously identified. However, the evolutionary history of these members remains largely unclear. In this study, we collected the MAPK genes from vertebrates, inLY2157299 structure vertebrates and plants to draw the most comprehensive evolutionary scenario of the vertebrate MAPK family. We found that vertebrates had substantially more MAPK family members than invertebrates , and the vertebrate MAPK family had been formed through multiple duplications at least prior to the diversification of teleosts . Intriguingly, after rapid extensive gene duplication events, not all vertebrates have all 13 MAPK family members . This might be attributed to two reasons. First, the genome sequences of the vertebrates analyzed were incomplete. Second, gene loss events might have happened in some vertebrate species, as observed in amphibians and teleosts, both of which lost some MAPK family members . These results suggest that a burst of gene duplication events and subsequent widespread gene deletion events , had occurred during the early evolution of the vertebrate MAPK family. In the phylogenetic analyses, six subclades were found, including MAPKs 1&3, MAPKs 4&6, MAPK7, MAPK15, JNK and P38 . The six subclades were consistent with previous classification of the MAPK family .