Motoneurone survival factor produced by muscle increases in parallel with messenger RNA sequences homologous to beta NGF-cDNA.

Motoneurone survival in culture is enhanced by growth factors present in embryonic rat muscles and denervated adult muscles: extracts from mature muscle and 2-day denervated mature muscle do not produce survival effects whereas extracts from embryonic muscle and 4-day denervated mature muscle produce maximum survival effects. Here we show, using dot hybridization of mRNA with a 32P-labelled cDNA probe for beta-nerve growth factor (beta NGF), that mRNA sequences homologous to beta NGF appear in muscle in parallel with increased motoneurone survival activity. RNA gel blot hybridizations show that embryonic mRNA contains a sequence in the same molecular weight range as the mRNA for beta NGF.