title: BMP2 is required for early heart development during a distinct time period.
abstract: BMP2, like its Drosophila homologue dpp, is an important signaling molecule for specification of cardiogenic mesoderm in vertebrates. Here, we analyzed the time-course of BMP2-requirement for early heart formation in whole chick embryos and in explants of antero-lateral plate mesoderm. Addition of Noggin to explants isolated at stage 4 and cultured for 24 h resulted in loss of NKX2.5, GATA4, eHAND, Mef2A and vMHC expression. At stages 5-8 the individual genes showed differential sensitivity to Noggin addition. While expression of eHAND, NKX2.5 and Mef2A was clearly reduced by Noggin vMHC was only marginally affected. In contrast, GATA4 expression was enhanced after Noggin treatment. The developmental period during which cardiac mesoderm required the presence of BMP signaling in vivo was assessed by implantation of Noggin expressing cells into stage 4-8 embryos which were then cultured until stage 10-11. Complete loss of NKX2.5 and eHAND expression was observed in embryos implanted at stages 4-6, and expression was still suppressed in stages 7 and 8 implanted embryos. GATA4 expression was also blocked by Noggin at stage 4, however increased at stages 5, 6 and 7. Explants of central mesendoderm, that normally do not form heart tissue were employed to study the time-course of BMP2-induced cardiac gene expression. The induction of cardiac lineage markers in central mesendoderm of stage 5 embryos was distinct for different genes. While GATA4, -5, -6 and MEF2A were induced to maximal levels within 6 h after BMP2 addition, eHAND and dHAND required 12 h to reach maximum levels of expression. NKX2.5 was induced by 6 h and accumulated over 48 h. vMHC and titin were induced at significant levels only after 48 h of BMP2 addition. These results indicate that cardiac marker genes display distinct expression kinetics after BMP2 addition and differential response to Noggin treatment suggesting complex regulation of myocardial gene expression in the early tubular heart.
authors.affiliation: Department of Cell and Molecular Biology, Institute of Biochemistry and Biotechnology, Technical University of Braunschweig, Spielmannstrasse 7, 38106, Braunschweig, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Schlange
authors.forename: B
authors.initials: B
authors.lastname: Andrée
authors.forename: H H
authors.initials: HH
authors.lastname: Arnold
authors.forename: T
authors.initials: T
authors.lastname: Brand
mesh_terms: D000818:Animals; D015415:Biomarkers; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000378:metabolism* / Q000494:pharmacology; D016466:CHO Cells; D002352:Carrier Proteins; D002642:Chick Embryo; D006224:Cricetinae; D004268:DNA-Binding Proteins / Q000235:genetics; D004707:Endoderm; D050991:GATA4 Transcription Factor; D050992:GATA5 Transcription Factor; D050993:GATA6 Transcription Factor; D005786:Gene Expression Regulation; D006321:Heart / Q000196:embryology*; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D011506:Proteins / Q000378:metabolism; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics; D016212:Transforming Growth Factor beta; D000099176:Noggin Protein
chemical_list: D015415:Biomarkers; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D050991:GATA4 Transcription Factor; D050992:GATA5 Transcription Factor; D050993:GATA6 Transcription Factor; D011506:Proteins; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D000099176:Noggin Protein