Two myogenin-related genes are differentially expressed in Xenopus laevis myogenesis and differ in their ability to transactivate muscle structural genes.
Among the myogenic regulatory factors, myogenin is a transcriptional activator situated at a crucial position for terminal differentiation in muscle development. It is unclear at present whether myogenin exhibits unique specificities to transactivate late muscular markers. During Xenopus development, the accumulation of myogenin mRNA is restricted to secondary myogenesis, at the onset of the appearance of adult isoforms of beta-tropomyosin and myosin heavy chain. To determine the role of myogenin in the isoform switch of these contractile proteins, we characterized and directly compared the functional properties of myogenin with other myogenic regulatory factors in Xenopus embryos. Two distinct cDNAs related to myogenin, XmyogU1 and XmyogU2, were differentially expressed during myogenesis and in adult tissues, in which they preferentially accumulated in oxidative myofibers. Animal cap assays in Xenopus embryos revealed that myogenin, but not the other myogenic regulatory factors, induced expression of embryonic/larval isoforms of the beta-tropomyosin and myosin heavy chain genes. Only XmyogU1 induced expression of the adult fast isoform of the myosin heavy chain gene. This is the first demonstration of a specific transactivation of one set of muscle structural genes by myogenin.
Charbonnier
Frederic
F
Laboratoire de Biologie du Développement et de la Différenciation Musculaire (EA 2507), Centre Universitaire des Saints-Pères, Université René Descartes, F-75270 Paris Cedex 06, France. chanoine@biomedicale.univ-paris5.fr
Gaspera
Bruno Della
BD
Armand
Anne-Sophie
AS
Van der Laarse
Willem J
WJ
Launay
Thierry
T
Becker
Christel
C
Gallien
Claude-Louis
CL
Chanoine
Christophe
C
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004625:Embryo, Nonmammalian / Q000502:physiology; D005260:Female; D005796:Genes / Q000235:genetics*; D006801:Humans; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D024510:Muscle Development / Q000502:physiology*; D009132:Muscles / Q000166:cytology / Q000502:physiology*; D018006:Myogenic Regulatory Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018008:Myogenin / Q000235:genetics* / Q000378:metabolism; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000378:metabolism; D015533:Transcriptional Activation / Q000502:physiology*; D029867:Xenopus Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis / Q000196:embryology / Q000502:physiology*
C503799:MYOG protein, human; D018006:Myogenic Regulatory Factors; D018008:Myogenin; D020033:Protein Isoforms; D012333:RNA, Messenger; D029867:Xenopus Proteins; C446022:XmyogU1 protein, Xenopus; C446023:XmyogU2 protein, Xenopus