Tissue-specific and ubiquitous basic helix-loop-helix transcription factors in human placental trophoblasts.
Tissue-specific class B basic helix-loop-helix (bHLH) transcription factors, dimerising with ubiquitously produced class A bHLH proteins, play a major role in murine trophoblast development. Here, we investigated expression patterns of class A and B bHLH factors in the human placenta and different trophoblast culture systems. Semi-quantitative RT-PCR and RNase protection assay revealed expression of the tissue-restricted factors Hash-2, I-mfa and Stra13 in placentae of early and late pregnancy, in purified villous trophoblasts as well as in invasive trophoblasts isolated from first trimester villous explant cultures. Accordingly, RNA in situ hybridisation localised Hash-2, I-mfa and Stra13 to the trophoblast epithelium, cell columns and extravillous trophoblasts invading maternal decidua. Villous stromal cells in situ and cultivated placental fibroblasts also produced I-mfa and Stra13 but failed to express Hash-2. The widely expressed class A proteins, E12/E47 were absent from all placental cell types while ITF-2 was restricted to placental stromal cells of early and late gestation. In contrast, HEB was identified in all trophoblast cell types using RT-PCR, Western blotting and immunohistochemistry. The negative HLH-regulators Id-1 and Id-2 lacking the DNA-binding domain, were detected in villous stromal cells and different cytotrophoblast subtypes but were absent from the syncytium. The data suggest that a complex interplay of activators (Hash-2, HEB) and repressors (Stra13, I-mfa) could be involved in extravillous trophoblast differentiation whereas downregulation of Id proteins could play a role in syncytialisation.
Department of Obstetrics and Gynecology, Medical University of Vienna, AKH, Waehringer Guertel 18-20, A-1090 Vienna, Austria.
G
G
Meinhardt
P
P
Husslein
M
M
Knöfler
D000328:Adult; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D015153:Blotting, Western; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002824:Chorionic Villi / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005865:Gestational Age; D018257:Helix-Loop-Helix Motifs / Q000502:physiology*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D018006:Myogenic Regulatory Factors / Q000235:genetics / Q000378:metabolism; D011247:Pregnancy; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017154:Stromal Cells / Q000166:cytology / Q000378:metabolism; D051820:TCF Transcription Factors; D000073940:Transcription Factor 4; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014327:Trophoblasts / Q000166:cytology / Q000378:metabolism*
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D018006:Myogenic Regulatory Factors; D012333:RNA, Messenger; D051820:TCF Transcription Factors; D000073940:Transcription Factor 4; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors; C065501:ASCL2 protein, human; C107989:BHLHE40 protein, human; C532096:TCF4 protein, human; C544894:TCF7L2 protein, human; C101295:MDFI protein, human