Cardiac myosin heavy chain expression during heart development in Xenopus laevis.
Muscle-specific gene expression in the heart during Xenopus development was investigated using reverse transcription-polymerase chain reaction (RT-PCR) and whole-mount in situ hybridization to detect transcripts of the gene for the cardiac myosin heavy chain (CMHC). RT-PCR analysis determined that CMHC transcripts are present in the cardiac mesoderm at state 13, demonstrating that muscle-specific gene expression in the primitive myocardium has begun by the early neurula stage, approximately 30 h before the heart beat begins. Xenopus, therefore, is similar to amniotes and mammals in that cardiac precursor cells begin to express muscle-specific gene transcripts soon after commitment to the cardiac myocyte lineage. The earliest CMHC gene transcripts can be detected in the heart using whole-mount in situ hybridization is early tailbud stage 28, which coincides with the onset of heart tube morphogenesis. CMHC gene expression was also detected in skeletal muscle: RT-PCR analysis determined that CMHC transcripts are transiently expressed in the somite during the initial phases of skeletal muscle differentiation. Furthermore, CMHC mRNAs are expressed in a subset of head muscles of the feeding tadpole. CMHC gene expression is induced in ectodermal cells of the animal cap in blastula-stage embryos injected with synthetic MyoD or Myf5 RNA, suggesting that the CMHC gene contains regulatory elements that are responsive to the activity of those skeletal-muscle-specific transcription factors.
Cox
W G
WG
Medical Sciences Program, Indiana University, School of Medicine, Bloomington 47405, USA.
Neff
A W
AW
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D018507:Gene Expression Regulation, Developmental; D006321:Heart / Q000196:embryology / Q000254:growth & development / Q000502:physiology*; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D009218:Myosins / Q000096:biosynthesis* / Q000235:genetics*; D009928:Organ Specificity; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D014982:Xenopus laevis / Q000196:embryology*
D018076:DNA, Complementary; D009218:Myosins