Fibroblast growth factor-8b-stimulated myogenic cell proliferation is suppressed by the promyelocytic leukemia gene.
Muscle cell growth is regulated by growth-promoting and -inhibiting factors. In this study, the physiological effects of fibroblast growth factor (FGF)-8b and the promyelocytic leukemia (PML) gene on G8 myogenic cells were examined. FGF-8b was found to strongly stimulate myogenic cell proliferation. Signal transduction assays using AP-1/SEAP and E-box/SEAP reporters revealed that the transcriptional factors junB/c-fos and c-myc were involved in FGF-8b-stimulated G8 cell growth. Besides examining factors that positively stimulate myogenic cell growth, we also examined genes that negatively affect cell growth. PML is a growth suppressor gene and we studied its expression in G8 cells under different growth conditions. Immunohistochemical staining revealed that in the presence of low serum, PML was expressed in approximately 23.2% of all cultured G8 cells. However, under normal culture conditions (10% serum), PML expression dropped to about 2.6%. We found that the PML gene acted antagonistically to FGF-8b, as the overexpression of PML in G8 cells significantly inhibited FGF-8b-stimulated cell proliferation. It also inhibited AP-1 and E-box transactivation. However, we believe that PML functions as a stress-response gene in G8 cells rather than as a gene normally involved in regulating muscle development.
Kwong
W H
WH
Department of Anatomy, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong, People's Republic of China.
Tang
M K
MK
Yew
D T
DT
Chan
J Y
JY
Cai
D Q
DQ
Tong
W M
WM
Lee
K K
KK
D000818:Animals; D001790:Blood Physiological Phenomena; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured / Q000187:drug effects; D003470:Culture Media / Q000494:pharmacology; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000502:physiology*; D017930:Genes, Reporter; D005813:Genes, Synthetic; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000032:analysis / Q000235:genetics; D051379:Mice; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects*; D009363:Neoplasm Proteins / Q000502:physiology*; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic; D000071156:Promyelocytic Leukemia Protein; D020033:Protein Isoforms / Q000235:genetics / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D012045:Regulatory Sequences, Nucleic Acid; D015398:Signal Transduction; D013312:Stress, Physiological / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic; D014162:Transfection; D025521:Tumor Suppressor Proteins
D003470:Culture Media; C496457:Fgf8 protein, mouse; D008164:Luminescent Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; C513293:Pml protein, mouse; D000071156:Promyelocytic Leukemia Protein; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D049452:Green Fluorescent Proteins; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors