title: Extracellular signal-regulated kinase 2 is necessary for mesoderm differentiation.
abstract: The extracellular signal-regulated kinase (ERK) is a component of the mitogen-activated protein kinase cascade. Exon 2 of erk2 was deleted by homologous recombination and resulted in embryonic lethality at embryonic day 6.5. erk2 mutant embryos did not form mesoderm and showed increased apoptosis but comparable levels of BrdUrd incorporation, indicating a defect in differentiation. erk2 null embryonic stem (ES) cells exhibited reduced total ERK activity upon serum stimulation, augmented ERK1 phosphorylation, and decreased downstream p90Rsk phosphorylation and activity; yet ES cell proliferation was unaffected. Mutant ES cells were capable of forming mesoderm; however, treatment of mutant ES cells with the mitogen-activated protein kinase kinase inhibitor PD184352 decreased total ERK activity and expression of the mesodermal marker brachyury, suggesting that ERK1 can compensate for ERK2 in vitro. Normal embryos at embryonic day 6.5 expressed activated ERK1/2 in the extraembryonic ectoderm, whereas erk2 mutant embryos had no detectable activated ERK1/2 in this region, suggesting that activated ERK1 was not expressed, and therefore cannot compensate for loss of ERK2 in vivo. These data indicate that ERK2 plays an essential role in mesoderm differentiation during embryonic development.
authors.affiliation: Department of Biology, Vertex Pharmaceuticals, 130 Waverly Street, Cambridge, MA 02139, USA.
authors.forename: Yao
authors.initials: Y
authors.lastname: Yao
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Junwei
authors.initials: J
authors.lastname: Wu
authors.forename: Ursula A
authors.initials: UA
authors.lastname: Germann
authors.forename: Michael S S
authors.initials: MS
authors.lastname: Su
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kuida
authors.forename: Diane M
authors.initials: DM
authors.lastname: Boucher
mesh_terms: D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology*; D002455:Cell Division; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006579:Heterozygote; D008648:Mesoderm / Q000166:cytology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D013234:Stem Cells
chemical_list: C120227:2-(2-chloro-4-iodophenylamino)-N-cyclopropylmethoxy-3,4-difluorobenzamide; D001549:Benzamides; D004791:Enzyme Inhibitors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases