title: Skeletal and cardiac alpha-actin isoforms exhibit unanticipated temporal and tissue-specific gene expression patterns in developing avian limbs and embryos.
abstract: The initial expression of skeletal muscle structural genes typically occurs after myogenic determination factor gene expression. We investigated this temporal relationship via a reverse transcription-polymerase chain reaction (RT-PCR) analysis of skeletal and cardiac alpha-actin (s- and c-actin) mRNA during chick limb development. c-actin transcripts were first detected at the beginning of muscle cytodifferentiation in stage 24/25 limbs, shortly after the initial appearance of MyoD and myogenin mRNAs, and were not detected in nonmyogenic tissues. In contrast, s-actin mRNA was detected in limbs at stage 15-16, periods when myf5 and MRF4 but not MyoD and myogenin transcripts are present (Lin-Jones, J., and Hauschka, S. D., Dev. Biol. 174, 407-422, 1996). While s-actin mRNA was not detected in E7 neural retina and was at variable levels in stage 9-15 neural tube, significant levels were consistently detected in mesodermal tissues which contribute nonmyogenic cells to the limb: stage 9-12 lateral plate and distal portions of stage 25/26 limbs. s-actin transcripts detected in the earliest limbs could thus be in myogenic and/or nonmyogenic cells. These data indicate that while c-actin expression is activated at the onset of limb muscle cytodifferentiation, s-actin expression occurs much earlier, as well as in some nonmyogenic tissues. Whether the precocious expression of s-actin plays a functional role in muscle development remains to be determined.
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA.
authors.forename: J
authors.initials: J
authors.lastname: Lin-Jones
authors.forename: S D
authors.initials: SD
authors.lastname: Hauschka
mesh_terms: D000199:Actins / Q000235:genetics* / Q000502:physiology; D000818:Animals; D002642:Chick Embryo; D004268:DNA-Binding Proteins; D005121:Extremities / Q000196:embryology*; D015870:Gene Expression; D005796:Genes; D006321:Heart / Q000196:embryology*; D018878:Limb Buds / Q000378:metabolism; D009124:Muscle Proteins / Q000235:genetics; D018482:Muscle, Skeletal / Q000196:embryology* / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D051787:Myogenic Regulatory Factor 5; D018006:Myogenic Regulatory Factors / Q000235:genetics; D016133:Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D015534:Trans-Activators / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics
chemical_list: D000199:Actins; D004268:DNA-Binding Proteins; D009124:Muscle Proteins; D051787:Myogenic Regulatory Factor 5; D018006:Myogenic Regulatory Factors; D015534:Trans-Activators; D014157:Transcription Factors; C063403:myogenic factor 6