Relationship of insulin-like growth factor II gene expression in muscle to synaptogenesis.
A striking correlation between insulin-like growth factor II (IGF-II) gene expression and turnover of neuromuscular synapses was observed. The IGF-II gene was expressed at a high level in fetal rat hind limb muscles prior to the developmental formation of synapses and increased while polyneuronal innervation accumulated. Thereafter, there was a selective down-regulation of IGF-II mRNAs that was exactly coincident with the postnatal time course for elimination of superfluous synapses. The hypothesis that innervation might provide a signal suppressing IGF-II gene expression was tested. Upon transection of the sciatic nerve, there was up-regulation of IGF-II mRNA content in muscle. This up-regulation was selective and correlated with the capacity of denervated muscle to accept reinnervation. These results suggest that the IGF-II gene may play a role in the development and turnover of synapses.
Ishii
D N
DN
Department of Physiology, Colorado State University, Fort Collins 80523.
D000818:Animals; D015152:Blotting, Northern; D002454:Cell Differentiation; D005786:Gene Expression Regulation; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D009121:Muscle Denervation; D024510:Muscle Development; D009132:Muscles / Q000166:cytology / Q000294:innervation / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D013002:Somatomedins / Q000235:genetics*; D013569:Synapses / Q000502:physiology*; D013997:Time Factors
D012333:RNA, Messenger; D013002:Somatomedins; D007335:Insulin-Like Growth Factor II