title: Fibroblast growth factor 4-induced migration of porcine trophectoderm cells is mediated via the AKT cell signaling pathway.
abstract: During early pregnancy, a well-coordinated communication network between the conceptus and maternal uterus is especially crucial in pigs in which there is a protracted pre-attachment phase prior to implantation. This network is regulated by an astonishing number of molecules such as growth factors. Fibroblast growth factor 4 (FGF4) is a multipotent growth factor that elicits diverse biological actions on various types of cells and tissues. In pigs, FGF4 and its receptors are expressed in the uterine endometrium and conceptus during early pregnancy, but less is known about the FGF4-mediated regulation of conceptus growth during peri-implantation period of pregnancy. Therefore, the aims of the present study were to investigate: 1) expression of endometrial FGF4 mRNA during early pregnancy; 2) up-regulation of FGF receptor expression in porcine trophectoderm (pTr) cells in response to FGF4; and 3) FGF-induced intracellular signaling and cellular activities in pTr cells. In vitro cultured pTr cells incubated with different concentrations of recombinant FGF4 (0-50 ng/ml) responded with a dose-dependent increase in AKT phosphorylation of 2.9-fold at 20 ng/ml FGF4. Within 30 min after treatment with 20 ng/ml FGF4, the abundances of p-AKT, p-P90RSK and p-RPS6 proteins increased 2.1-, 5.2- and 3.2-fold, respectively, and then returned to basal levels by 120 min. To ensure that the stimulatory effect of FGF4 on AKT signaling was p-AKT-dependent, pTr cells were pre-incubated with an AKT inhibitor (LY294002) for 1 h prior to FGF4 treatment. 20 μM of LY294002 decreased FGF4-induced p-AKT, p-P90RSK and p-RPS6 proteins. Immunofluorescence analyses revealed that p-RPS6 proteins were abundant within the cytoplasm of FGF4-treated cells, but present at basal levels in the presence of LY294002. Furthermore, FGF4 increased migration of pTr cells and LY294002 significantly reduced this effect. Results of the present study suggest that activation of the FGF receptor(s) on trophectoderm cells by FGF4 secreted by conceptus/endometrium transduces its signal through the phosphatidylinositol 3-kinase (PI3K)/AKT pathway which is linked to migration of trophectoderm cells that is critical to development of the porcine conceptus.
authors.affiliation: Department of Animal Resources Science, Dankook University, Cheonan, Republic of Korea.
authors.forename: Wooyoung
authors.initials: W
authors.lastname: Jeong
authors.affiliation: Department of Animal Resources Science, Dankook University, Cheonan, Republic of Korea.
authors.forename: Jieun
authors.initials: J
authors.lastname: Lee
authors.affiliation: Center for Animal Biotechnology and Genomics and Department of Animal Science, Texas A&M University, College Station, TX, USA.
authors.forename: Fuller W
authors.initials: FW
authors.lastname: Bazer
authors.affiliation: Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea. Electronic address: ghsong@korea.ac.kr.
authors.forename: Gwonhwa
authors.initials: G
authors.lastname: Song
authors.affiliation: Department of Animal Resources Science, Dankook University, Cheonan, Republic of Korea. Electronic address: jinyoungkim@dankook.ac.kr.
authors.forename: Jinyoung
authors.initials: J
authors.lastname: Kim
mesh_terms: D000818:Animals; D002465:Cell Movement; D002478:Cells, Cultured; D004475:Ectoderm / Q000166:cytology* / Q000378:metabolism; D005260:Female; D051519:Fibroblast Growth Factor 4 / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics; D011247:Pregnancy; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics*; D017468:Receptors, Fibroblast Growth Factor / Q000235:genetics; D015398:Signal Transduction; D013552:Swine; D014327:Trophoblasts / Q000166:cytology* / Q000378:metabolism
chemical_list: D051519:Fibroblast Growth Factor 4; D017468:Receptors, Fibroblast Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt
keywords: FGF4; Peri-implantation; Pig; Trophectoderm; Trophoblast