title: Fibroblast growth factor 2 promotes primitive endoderm development in bovine blastocyst outgrowths.
abstract: Primitive endoderm (PE) is the second extraembryonic tissue to form during embryogenesis in mammals. The PE develops from pluripotent cells of the blastocyst inner cell mass. Experimental results described herein provide evidence that FGF2 stimulates PE development during bovine blastocyst development in vitro. Bovine blastocysts were cultured individually on a feeder layer-free, Matrigel-coated surface in the presence or absence of FGF2. A majority of blastocysts cultures formed outgrowths (76.8%) and the rate of outgrowth formation was not affected by FGF2 supplementation. However, supplementation with FGF2 increased the incidence of PE outgrowths on Days 13 and 15 after in vitro fertilization. Presumptive PE cultures contained cells with a phenotype distinct from trophectoderm (TE). Cell identity was validated by expression of GATA4 and GATA6 mRNA and transferrin protein, all markers of the PE lineage. Expression of GATA4 occurred coincident with blastocyst expansion and hatching. These cells did not express IFNT and CDX2 (TE lineage markers). Profiles of FGF receptor (FGFR) isoforms were distinct between PE and TE cultures. Specifically, FGFR1b and FGFR1c were the predominant FGFR transcripts in PE whereas FGFR2b transcripts were abundant in TE. Supplementation with FGF2 increased the mitotic index of PE but not TE. Moreover, FGF signaling appears important for initiation of PE formation in blastocysts, presumably by lineage committal from NANOG-positive epiblast cells, because chemical disruption of FGFR kinase activity with PD173074 reduces GATA4 expression and increases NANOG expression. Collectively, these results indicate that FGF2 and potentially other FGFs specify PE formation and mediate PE proliferation during early pregnancy in cattle.
authors.affiliation: Department of Animal Sciences, University of Florida, Gainesville, Florida 32611-0910, USA.
authors.forename: Qi En
authors.initials: QE
authors.lastname: Yang
authors.forename: Sarah D
authors.initials: SD
authors.lastname: Fields
authors.forename: Kun
authors.initials: K
authors.lastname: Zhang
authors.forename: Manabu
authors.initials: M
authors.lastname: Ozawa
authors.forename: Sally E
authors.initials: SE
authors.lastname: Johnson
authors.forename: Alan D
authors.initials: AD
authors.lastname: Ealy
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001755:Blastocyst / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D002417:Cattle / Q000196:embryology*; D049109:Cell Proliferation / Q000187:drug effects*; D046149:Embryo Culture Techniques; D004707:Endoderm / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D050991:GATA4 Transcription Factor / Q000235:genetics / Q000378:metabolism; D050993:GATA6 Transcription Factor / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D023421:Models, Animal; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
chemical_list: D015415:Biomarkers; D050991:GATA4 Transcription Factor; D050993:GATA6 Transcription Factor; D016222:Fibroblast Growth Factor 2