Cell history determines the maintenance of transcriptional differences between left and right ventricular cardiomyocytes in the developing mouse heart.
The molecular mechanisms that establish and maintain transcriptional differences between cardiomyocytes in the left and right ventricular chambers are unkown. We have previously analysed a myosin light chain 3f transgene containing an nlacZ reporter gene, which is transcribed in left but not right ventricular cardiomyocytes. In this report we examine the mechanisms involved in maintaining regionalised transgene expression. Primary cardiomyocytes prepared from left and right ventricular walls of transgenic mice were found to maintain transgene expression status in culture. However, similar cultures prepared from nontransgenic mice or rats show uniform expression after transient transfection of Mlc3f constructs, suggesting that the mechanism responsible for differential expression of the transgene between left and right ventricular cells does not operate on transiently introduced molecules. These data suggest that developmental cell history determines transgene expression status. Maintenance of transgene expression status is regulated by a cell-autonomous mechanism that is independent of DNA methylation, trichostatin A-sensitive histone deacetylation and miss-expression of transcription factors that are expressed in the left or right ventricles of the embryonic heart. Parallels between Mlc3f transgene repression in right ventricular cardiomyocytes and polycomb-mediated silencing in Drosophila suggest that Mlc3f regulatory sequences included on the transgene may contain a cellular memory module that is switched into an on or off state during early cardiogenesis. Epigenetic mechanisms may therefore be involved in maintaining patterning of the mammalian myocardium.
Kelly
Robert G
RG
CNRS URA 2578, Department of Developmental Biology, Pasteur Institute, 25 Rue du Dr Roux, Paris 75015, France. rkelly@pasteur.fr
Lemonnier
Marguerite
M
Zaffran
Stephane
S
Munk
Andrew
A
Buckingham
Margaret E
ME
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter / Q000502:physiology; D006352:Heart Ventricles / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D009206:Myocardium / Q000166:cytology / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000378:metabolism; D018994:Myosin Light Chains / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D020825:T-Box Domain Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D029961:Zebrafish Proteins
D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D018994:Myosin Light Chains; D020825:T-Box Domain Proteins; D014157:Transcription Factors; D029961:Zebrafish Proteins; C095572:Hand1 protein, mouse; C498766:Hand2 protein, mouse; C498767:Hand2 protein, rat; C103172:T-box transcription factor 5; C410915:hand2 protein, zebrafish; C097341:helix-loop-helix protein, eHAND