title: RNA from normal anterior endoderm/mesoderm-conditioned medium stimulates myofibrillogenesis in developing mutant axolotl hearts.
abstract: In the axolotl, Ambystoma mexicanum, a recessive cardiac lethal mutation causes an incomplete differentiation of the myocardium. Mutant hearts do not contain sarcomeric myofibrils nor do they beat. We have previously shown that normal anterior endoderm, medium conditioned by endoderm, or total RNA extracted from endoderm stimulates differentiation of mutant hearts in culture as indicated by the presence of organized myofibrils and rhythmic contractions of the "rescued" mutant heart tube. In this study, to get a more highly purified sample of the "active" molecule, RNA extracted from endoderm-conditioned medium and was assayed for its ability to promote myofibrillogenesis in mutant hearts. Mutant heart mesoderm responded to conditioned-medium RNA in a dose-dependent manner. Proteinase K treatment of the RNA did not affect inductive activity, while digestion with RNase A completely abolished the ability to rescue mutant hearts. Confocal laser scanning microscopy of immunostained, organ-cultured hearts revealed that mutant hearts contain reduced amounts of the sarcomeric protein tropomyosin in an amorphous distribution, whereas normal and corrected mutant hearts contain tropomyosin primarily in organized myofibrils.
authors.affiliation: SUNY Health Science Center, Department of Anatomy and Cell Biology, Syracuse 13210.
authors.forename: S M
authors.initials: SM
authors.lastname: LaFrance
authors.forename: M E
authors.initials: ME
authors.lastname: Fransen
authors.forename: N
authors.initials: N
authors.lastname: Erginel-Unaltuna
authors.forename: D K
authors.initials: DK
authors.lastname: Dube
authors.forename: D R
authors.initials: DR
authors.lastname: Robertson
authors.forename: C
authors.initials: C
authors.lastname: Stefanu
authors.forename: T K
authors.initials: TK
authors.lastname: Ray
authors.forename: L F
authors.initials: LF
authors.lastname: Lemanski
mesh_terms: D000557:Ambystoma / Q000196:embryology / Q000235:genetics*; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D017077:Culture Media, Conditioned / Q000737:chemistry; D004707:Endoderm / Q000378:metabolism*; D005804:Genes, Lethal; D006321:Heart / Q000187:drug effects / Q000196:embryology*; D008648:Mesoderm / Q000378:metabolism*; D009024:Morphogenesis / Q000187:drug effects; D009206:Myocardium / Q000648:ultrastructure*; D009210:Myofibrils / Q000187:drug effects* / Q000378:metabolism; D012313:RNA / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D014335:Tropomyosin / Q000172:deficiency* / Q000502:physiology
chemical_list: D017077:Culture Media, Conditioned; D014335:Tropomyosin; D012313:RNA