title: Trophectoderm lineage determination in cattle.
abstract: The trophectoderm (TE) and inner cell mass (ICM) are committed and marked by reciprocal expression of Cdx2 and Oct4 in mouse late blastocysts. We find that the TE is not committed at equivalent stages in cattle, and that bovine Cdx2 is required later, for TE maintenance, but does not repress Oct4 expression. A mouse Oct4 (mOct4) reporter, repressed in mouse TE, remained active in the cattle TE; bovine Oct4 constructs were not repressed in the mouse TE. mOct4 has acquired Tcfap2 binding sites mediating Cdx2-independent repression-cattle, humans, and rabbits do not contain these sites and maintain high Oct4 levels in the TE. Our data suggest that the regulatory circuitry determining ICM/TE identity has been rewired in mice, to allow rapid TE differentiation and early blastocyst implantation. These findings thus emphasize ways in which mice may not be representative of the earliest stages of mammalian development and stem cell biology.
authors.affiliation: Reproductive Technologies, AgResearch Crown Research Institute, Hamilton 3214, New Zealand.
authors.forename: Debra K
authors.initials: DK
authors.lastname: Berg
authors.forename: Craig S
authors.initials: CS
authors.lastname: Smith
authors.forename: David J
authors.initials: DJ
authors.lastname: Pearton
authors.forename: David N
authors.initials: DN
authors.lastname: Wells
authors.forename: Ric
authors.initials: R
authors.lastname: Broadhurst
authors.forename: Martyn
authors.initials: M
authors.lastname: Donnison
authors.forename: Peter L
authors.initials: PL
authors.lastname: Pfeffer
mesh_terms: D000818:Animals; D001483:Base Sequence; D053624:Blastocyst Inner Cell Mass / Q000166:cytology / Q000378:metabolism; D002417:Cattle; D019070:Cell Lineage; D004475:Ectoderm / Q000166:cytology* / Q000196:embryology / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D050814:Octamer Transcription Factor-3 / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D011817:Rabbits; D013045:Species Specificity; D014158:Transcription, Genetic; D014327:Trophoblasts / Q000166:cytology* / Q000378:metabolism
chemical_list: D018398:Homeodomain Proteins; D050814:Octamer Transcription Factor-3