title: The ascidian Mesp gene specifies heart precursor cells.
abstract: Understanding the molecular basis of heart development is an important research area, because malformation of the cardiovascular system is among the most frequent inborn defects. Although recent research has identified molecules responsible for heart morphogenesis in vertebrates, the initial specification of heart progenitors has not been well characterized. Ascidians provide an appropriate experimental system for exploring this specification mechanism, because the lineage for the juvenile heart is well characterized, with B7.5 cells at the 110-cell stage giving rise to embryonic trunk ventral cells (TVCs) or the juvenile heart progenitors. Here, we show that Cs-Mesp, the sole ortholog of vertebrate Mesp genes in the ascidian Ciona savignyi, is specifically and transiently expressed in the embryonic heart progenitor cells (B7.5 cells). Cs-Mesp is essential for the specification of heart precursor cells, in which Nkx, HAND and HAND-like (NoTrlc) genes are expressed. As a result, knockdown of Cs-Mesp with specific morpholino antisense oligonucleotides causes failure of the development of the juvenile heart. Together with previous evidence obtained in mice, the present results suggest that a mechanism for heart specification beginning with Mesp through Nkx and HAND is conserved among chordates.
authors.affiliation: Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan. yutaka@ascidian.zool.kyoto-u.ac.jp
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Satou
authors.forename: Kaoru S
authors.initials: KS
authors.lastname: Imai
authors.forename: Nori
authors.initials: N
authors.lastname: Satoh
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D019070:Cell Lineage; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004527:Egg Proteins / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006321:Heart / Q000196:embryology* / Q000254:growth & development; D047908:Intracellular Signaling Peptides and Proteins; D009024:Morphogenesis / Q000235:genetics; D009206:Myocardium / Q000166:cytology*; D013234:Stem Cells / Q000502:physiology; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014561:Urochordata / Q000196:embryology / Q000235:genetics*; D051176:beta Catenin
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D004527:Egg Proteins; D047908:Intracellular Signaling Peptides and Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D051176:beta Catenin; C097341:helix-loop-helix protein, eHAND; C420970:macho-1 protein, Halocynthia roretzi