title: Trophoblast stem cell maintenance by fibroblast growth factor 4 requires MEKK4 activation of Jun N-terminal kinase.
abstract: Trophoblast differentiation during placentation involves an epithelial-mesenchymal transition (EMT) with loss of E-cadherin and gain of trophoblast invasiveness. Mice harboring a point mutation that renders inactive the mitogen-activated protein kinase kinase kinase MEKK4 exhibit dysregulated placental development with increased trophoblast invasion. Isolated MEKK4 kinase-inactive trophoblast stem (TS) cells cultured under undifferentiating, self-renewing conditions in the presence of fibroblast growth factor 4 (FGF4) display increased expression of Slug, Twist, and matrix metalloproteinase 2 (MMP2), loss of E-cadherin, and hyperinvasion of extracellular matrix, each a hallmark of EMT. MEKK4 kinase-inactive TS cells show a preferential differentiation to Tpbp alpha- and Gcm1-positive trophoblasts, which are indicative of spongiotrophoblast and syncytiotrophoblast differentiation, respectively. FGF4-stimulated Jun N-terminal kinase (JNK) and p38 activity is markedly reduced in MEKK4 kinase-inactive TS cells. Chemical inhibition of JNK in wild-type TS cells induced a similar EMT response as loss of MEKK4 kinase activity, including inhibition of E-cadherin expression and increased expression of Slug, MMP2, Tpbp alpha, and Gcm1. Chromatin immunoprecipitation analyses revealed changes in AP-1 composition with increased Fra-2 and decreased Fra-1 and JunB binding to the regulatory regions of Gcm1 and MMP2 genes in MEKK4 kinase-inactive TS cells. Our results define MEKK4 as a signaling hub for FGF4 activation of JNK that is required for maintenance of TS cells in an undifferentiated state.
authors.affiliation: Department of Pharmacology and Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-7365, USA. amy_abell@med.unc.edu
authors.forename: Amy N
authors.initials: AN
authors.lastname: Abell
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Granger
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Johnson
authors.forename: Nicole
authors.initials: N
authors.lastname: Vincent-Jordan
authors.forename: Christopher F
authors.initials: CF
authors.lastname: Dibble
authors.forename: Gary L
authors.initials: GL
authors.lastname: Johnson
mesh_terms: D028341:Activins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D002403:Cathepsins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins; D004622:Embryo, Mammalian / Q000166:cytology / Q000502:physiology; D004789:Enzyme Activation; D005109:Extracellular Matrix; D005260:Female; D051519:Fibroblast Growth Factor 4 / Q000235:genetics / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D048768:MAP Kinase Kinase Kinase 4 / Q000235:genetics / Q000378:metabolism*; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism; D010920:Placenta / Q000166:cytology; D011247:Pregnancy; D015398:Signal Transduction / Q000502:physiology; D000071250:Snail Family Transcription Factors; D013234:Stem Cells / Q000166:cytology / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism; D014327:Trophoblasts / Q000166:cytology* / Q000502:physiology; D051879:Twist-Related Protein 1 / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D015820:Cadherins; D004268:DNA-Binding Proteins; D051519:Fibroblast Growth Factor 4; C101631:Gcm1 protein, mouse; D009479:Neuropeptides; C000604449:Snai2 protein, mouse; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D051879:Twist-Related Protein 1; D028341:Activins; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048768:MAP Kinase Kinase Kinase 4; D002403:Cathepsins; C028217:cathepsin S; D020778:Matrix Metalloproteinase 2