title: Mesp1-nonexpressing cells contribute to the ventricular cardiac conduction system.
abstract: Previous fate mapping analysis, using Cre recombinase driven by the Mesp1 locus, revealed that Mesp1 is expressed in almost all of the precursors of the cardiovascular system, including the endothelium, endocardium, myocardium, and epicardium. Mesp1-nonexpressing cells were found to be restricted to the outflow tract cushion and along the interventricular septum (IVS), which is a location that is suggestive of specialized cardiac conduction system (CCS). In our current study, we examined the identity of these IVS cells by using the pattern of beta-galactosidase activity in CCS-lacZ mice. In addition, by crossing Mesp1-Cre and floxed GFP reporter mice with CCS-lacZ mice, we have calculated that approximately 20% of the ventricular CCS within the IVS corresponds to Mesp1-nonexpressing cells. These data suggest that the ventricular CCS is of heterocellular origin. Furthermore, we indicate a possibility that a population of the cells that contribute to the ventricular CCS might be distinguished at an early stage of development.
authors.affiliation: Division of Cellular & Molecular Toxicology, Biological Safety Research Center, National Institute of Health Sciences, Setagaya-ku, Tokyo, Japan. satoshi@nihs.go.jp
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kitajima
authors.forename: Sachiko
authors.initials: S
authors.lastname: Miyagawa-Tomita
authors.forename: Tohru
authors.initials: T
authors.lastname: Inoue
authors.forename: Jun
authors.initials: J
authors.lastname: Kanno
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Saga
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D019070:Cell Lineage; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D006329:Heart Conduction System / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D006352:Heart Ventricles / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009432:Neural Crest / Q000166:cytology / Q000196:embryology / Q000378:metabolism
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; C101538:Mesp1 protein, mouse