title: Blastocyst implantation precedes induction of insulin-like growth factor II gene expression in human trophoblasts.
abstract: The cytotrophoblast cell population of the human embryonic conceptus proliferates rapidly during the first month following blastocyst implantation. Since the trophectoderm lineage is established in preimplantation morula/blastocysts, the scenario underlying initiation and maintenance of the rapid proliferative phenotype of cytotrophoblasts is a central issue. The insulin-like growth factor II (IGF-II) gene is highly expressed in proliferative cytotrophoblasts of first trimester placenta and performs as a placenta growth factor. To establish a temporal correlation between IGF-II expression and initiation of highly proliferative trophoblasts in human development, we employed in situ hybridization analysis of the expression of the IGF-II and human chorionic gonadotropin beta-subunit (beta-HCG) genes in human pre- and postimplantation development. The data show that the appearance of high steady-state levels of IGF-II transcripts in trophoblasts is a postimplantation event, whereas beta-HCG transcripts can already be detected in preimplantation development. This observation makes a role for endogenously produced IGF-II in the normal development of preimplantation embryos unlikely, but suggests that endogenously produced IGF-II participates in the formation and subsequent expansion of the rapid proliferative phenotype of the trophoblastic shell, following implantation.
authors.affiliation: Centre for Biotechnology, Karolinska Institute, Huddinge University Hospital, Sweden.
authors.forename: R
authors.initials: R
authors.lastname: Ohlsson
authors.forename: E
authors.initials: E
authors.lastname: Larsson
authors.forename: O
authors.initials: O
authors.lastname: Nilsson
authors.forename: T
authors.initials: T
authors.lastname: Wahlström
authors.forename: P
authors.initials: P
authors.lastname: Sundström
mesh_terms: D001755:Blastocyst / Q000502:physiology*; D004475:Ectoderm / Q000166:cytology / Q000502:physiology; D010064:Embryo Implantation; D005314:Embryonic and Fetal Development; D005260:Female; D015870:Gene Expression; D005796:Genes; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D009693:Nucleic Acid Hybridization; D015347:RNA Probes; D013002:Somatomedins / Q000235:genetics*; D014327:Trophoblasts / Q000502:physiology*
chemical_list: D015347:RNA Probes; D013002:Somatomedins; D007335:Insulin-Like Growth Factor II