title: Sox15 enhances trophoblast giant cell differentiation induced by Hand1 in mouse placenta.
abstract: Some members of the Sry-type HMG box (Sox) protein family play important roles in embryogenesis as transcription factors. Here, we report that Sox15 transcripts were much more abundant in mouse placenta than in the fetus, the yolk sac, or several adult tissues. In situ hybridization analysis of the mouse E8.0 conceptus indicated that Sox15 mRNA was predominantly expressed in the trophoblast giant cells of the placenta. We also observed that the amount of Sox15 mRNA dramatically increased during the differentiation of mouse trophoblast stem cells. Ectopic expression of Sox15 in Rat choriocarcinoma cells enhanced the giant cell differentiation induced by a bHLH transcription factor, Hand1. Binding experiments in cotransfected 293 T cells and in vitro revealed that Sox15 interacted with Hand1. We next examined the effects of this interaction on the transcriptional activity of Hand1 and Sox15 using the luciferase reporter assay. Overexpression of Hand1 repressed the Sox15-driven reporter expression, but Sox15 enhanced the Hand1-driven transcription. This enhancement required both the Hand1-binding region and the transactivation domain of Sox15. These results may suggest that the increased transcriptional activity of Hand1 caused by Sox15 might promote the transcription of the target gene resulting in the trophoblast giant cell differentiation in the mouse placenta.
authors.affiliation: Department of Biosciences, School of Science, Kitasato University, 1-15-1 Kitasato, Sagamihara, Kanagawa 228-8555, Japan.
authors.forename: Kayo
authors.initials: K
authors.lastname: Yamada
authors.forename: Hiromi
authors.initials: H
authors.lastname: Kanda
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tanaka
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Takamatsu
authors.forename: Tadayoshi
authors.initials: T
authors.lastname: Shiba
authors.forename: Michihiko
authors.initials: M
authors.lastname: Ito
mesh_terms: D000818:Animals; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000502:physiology*; D015152:Blotting, Northern; D016466:CHO Cells; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D006224:Cricetinae; D017931:DNA Primers; D018076:DNA, Complementary; D005260:Female; D017930:Genes, Reporter; D006609:High Mobility Group Proteins / Q000235:genetics / Q000502:physiology*; D006801:Humans; D017403:In Situ Hybridization; D051379:Mice; D010920:Placenta / Q000166:cytology*; D055747:SOX Transcription Factors; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014327:Trophoblasts / Q000166:cytology*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D006609:High Mobility Group Proteins; D055747:SOX Transcription Factors; D014157:Transcription Factors; C095572:Hand1 protein, mouse; C080886:Sox15 protein, mouse