Developmental shift of myosin heavy chain mRNA expression due to neural factor(s) and muscle activity.
The adult ventricular isoform of chicken myosin heavy chain (MHC-V) is transiently expressed in all skeletal muscle primordia analyzed and is completely repressed around embryonic days 10-12, when functional innervation is established. By ribonuclease protection assay, we demonstrated that denervation of the adult anterior latissimus dorsi muscle resulted in reexpression of MHC-V mRNA. In contrast, treatment of primary cultures of fetal breast or leg muscles with embryonic brain extract or conditioned media from glial or neuroblastoma cell lines, but not from a myogenic cell line or primary muscle cell cultures, led to inhibition of MHC-V expression. This inhibitory activity was abolished by heating and increased with protein concentration. The acquisition of both brain inhibitory activity and the competence of myogenic cells to downregulate MHC-V mRNA expression were age dependent. Furthermore, either paralysis of muscle in ovo by curare or contraction arrest of cultured myotubes resulted in persistent expression of MHC-V mRNA. Thus a putative soluble factor(s) of nerve origin as well as muscle activity are involved in the developmental downregulation of MHC-V expression in muscle primordia.
Camoretti-Mercado
B
B
Department of Medicine, University of Chicago, Illinois 60637, USA.
Qin
Y
Y
Jakovcic
S
S
Salazar-Grueso
E
E
Zak
R
R
D000367:Age Factors; D000818:Animals; D001921:Brain / Q000502:physiology; D002474:Cell-Free System; D002478:Cells, Cultured; D002642:Chick Embryo; D002645:Chickens; D015536:Down-Regulation; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D008297:Male; D009119:Muscle Contraction; D009121:Muscle Denervation; D018482:Muscle, Skeletal / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000235:genetics*; D010243:Paralysis / Q000503:physiopathology; D012333:RNA, Messenger / Q000235:genetics; D014403:Tubocurarine / Q000494:pharmacology; D015854:Up-Regulation
D012333:RNA, Messenger; D018995:Myosin Heavy Chains; D014403:Tubocurarine