Regulation of avian fibroblast growth factor receptor 1 (FGFR-1) gene expression during skeletal muscle differentiation.
Myogenic cell proliferation and differentiation are regulated by a fibroblast growth factor (FGF) signal transduction cascade mediated by a high-affinity fibroblast growth factor receptor (FGFR). Exogenous FGF added to myogenic cultures has a mitogenic effect promoting myoblast proliferation while repressing differentiation. We have examined the regulation of the FGFR-1 gene (cek-1) in avian myogenic cultures by immunocytochemistry and Northern blot analysis. FGFR-1 protein was readily detected in undifferentiated myoblast cultures and was significantly reduced in differentiated muscle fiber cultures. Similarly, FGFR-1 mRNA was 2.5-fold more abundant in myoblast cultures than in differentiated cultures. To define the molecular mechanism regulating FGFR-1 gene expression in proliferating myoblasts and post-mitotic muscle fibers, we have isolated and partially characterized the avian FGFR-1 gene promoter. Transfection of FGFR-1 promoter-chloramphenicol acetyltransferase gene constructs into myogenic cultures identified two regions regulating expression of this gene in myoblasts. A distal region of 2226 bp conferred a high level of expression in myoblasts. This region functioned in an orientation-dependent manner and interacted with a promoter element(s) in a proximal 1058 bp promoter region to direct transcription. Deletion analysis revealed a 78 bp region that confers a high level of cek1 promoter activity in myoblasts. This DNA segment also contains Spl binding sites and interacts with a component in myoblast nuclear protein extracts. The proximal promoter region alone demonstrated no activity in directing transcription in either myoblasts or muscle fibers. Using the full-length promoter, gene expression was significantly decreased in differentiated muscle fibers relative to undifferentiated myoblasts indicating that the promoter-reporter gene constructs contain elements regulating expression of the endogenous FGFR-1 gene in both myoblasts and muscle fibers.
Patel
S G
SG
Finch University of Health Sciences/The Chicago Medical School, Department of Cell Biology and Anatomy, North Chicago, IL 60064, USA.
Funk
P E
PE
DiMario
J X
JX
D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation / Q000235:genetics*; D002642:Chick Embryo; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D015252:Deoxyribonucleases, Type II Site-Specific / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D005346:Fibroblast Growth Factors / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D007150:Immunohistochemistry / Q000379:methods; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000166:cytology* / Q000196:embryology / Q000502:physiology; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D051496:Receptor, Fibroblast Growth Factor, Type 1; D017468:Receptors, Fibroblast Growth Factor / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic
D012333:RNA, Messenger; D017468:Receptors, Fibroblast Growth Factor; D011994:Recombinant Proteins; D005346:Fibroblast Growth Factors; D015500:Chloramphenicol O-Acetyltransferase; D020794:Receptor Protein-Tyrosine Kinases; D051496:Receptor, Fibroblast Growth Factor, Type 1; C052380:endodeoxyribonuclease NcoI; C024408:endodeoxyribonuclease SacI; D015252:Deoxyribonucleases, Type II Site-Specific