Atrial myocardium derives from the posterior region of the second heart field, which acquires left-right identity as Pitx2c is expressed.
Splanchnic mesoderm in the region described as the second heart field (SHF) is marked by Islet1 expression in the mouse embryo. The anterior part of this region expresses a number of markers, including Fgf10, and the contribution of these cells to outflow tract and right ventricular myocardium has been established. We now show that the posterior region also has myocardial potential, giving rise specifically to differentiated cells of the atria. This conclusion is based on explant experiments using endogenous and transgenic markers and on DiI labelling, followed by embryo culture. Progenitor cells in the right or left posterior SHF contribute to the right or left common atrium, respectively. Explant experiments with transgenic embryos, in which the transgene marks the right atrium, show that atrial progenitor cells acquire right-left identity between the 4- and 6-somite stages, at the time when Pitx2c is first expressed. Manipulation of Pitx2c, by gain- and loss-of-function, shows that it represses the transgenic marker of right atrial identity. A repressive effect is also seen on the proliferation of cells in the left sinus venosus and in cultured explants from the left side of the posterior SHF. This report provides new insights into the contribution of the SHF to atrial myocardium and the effect of Pitx2c on the formation of the left atrium.
Galli
Daniela
D
Department of Developmental Biology, URA 2578 CNRS, Pasteur Institute, 25 rue du Docteur Roux, 75724 Paris, France.
Domínguez
Jorge N
JN
Zaffran
Stephane
S
Munk
Andrew
A
Brown
Nigel A
NA
Buckingham
Margaret E
ME
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D005260:Female; D005318:Fetal Heart / Q000196:embryology* / Q000378:metabolism*; D051526:Fibroblast Growth Factor 10 / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D005822:Genetic Vectors; D006325:Heart Atria / Q000196:embryology / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism*; D060850:LIM-Homeodomain Proteins; D007763:Lac Operon; D051379:Mice; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D009206:Myocardium / Q000378:metabolism*; D011247:Pregnancy; D019170:Somites / Q000196:embryology / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D000097577:Homeobox Protein PITX2
D017931:DNA Primers; D051526:Fibroblast Growth Factor 10; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D014157:Transcription Factors; D000097577:Homeobox Protein PITX2; C496464:Fgf10 protein, mouse; C063843:insulin gene enhancer binding protein Isl-1