Characterization and expression patterns of the MAPK family in zebrafish.

The mitogen activated protein kinases (MAPK) family pathway is conserved in evolution through the plant and animal kingdoms. These proteins have been implicated in diverse cellular processes including cell growth, proliferation, differentiation, survival and development. In this study we annotated and cloned members of the zebrafish MAPK gene-family, containing the ERK, JNK and p38 subfamilies. Their sequences were compared to orthologs of other vertebrates (human, mouse and rat) and the temporal and spatial expression levels of the zebrafish mapk genes were determined during early zebrafish development. Semi-quantitative reverse transcriptase-PCR analysis revealed that most mapk genes are expressed throughout zebrafish development. Erk2,3 and p38a were expressed at a constant level throughout zebrafish embryogenesis, whereas erk1,4,5,6,7 and p38b showed specific temporal expression patterns. The spatial expression patterns were obtained by whole mount in situ hybridization at 24 h post fertilization (hpf) and 48 hpf embryos. The expression patterns were localized in specific regions at both stages and were tightly regulated during embryogenesis. For p38b, no staining was detected at 24 and 48 hpf. However, its expression was demonstrated at blastula-stage. Together, we identified the zebrafish orthologs of the zebrafish MAPK gene family and determined their specific spatial and temporal expression and distribution patterns during zebrafish embryogenesis.