EXPRESSION OF TRK AND NEUROTROPHIN MESSENGER-RNA IN DORSAL-ROOT AND SYMPATHETIC-GANGLIA OF THE QUAIL DURING DEVELOPMENT

The nerve growth factor (NGF) family of neurotrophins exerts effects b y binding to products of the trk family of proto-oncogenes. We examine d the expression of both trk and neurotrophin mRNA during the entire r ange of development of quail dorsal root ganglia (DRG) and sympathetic ganglia (SG) using in situ hybridization and reverse transcriptase-po lymerase chain reaction (RT-PCR). TrkC mRNA was present in neurons or their precursors from the time of formation of DRG (stage 18, embryoni c day 2.5 [E2.5]) and throughout development. The number of labeled ce lls changed, however, from a majority to a minority at later developme ntal stages. Expression of trkA mRNA was not detected in DRG until sta ge 30 (E6) by in situ hybridization, although results with RT-PCR were positive at stage 23(E3.5). Labeling was always detected on a majorit y of neurons or their precursors. SG exhibited low levels of trkC mRNA during the later stages of development, whereas trkA mRNA was present from stage 34 onward in most neurons. We have also shown that NGF, ne urotrophin-3 (NT-3), and brain-derived neurotrophic factor(BDNF) mRNA were present at all stages examined (stages 23 through 45 for DRG, sta ges 35-36 and 45 for SG). In DRG, NGF mRNA expression was limited to s upport cells, whereas NT-3 and BDNF mRNA were detected in both neurons and support cells. These results suggest that neurotrophins could ser ve a local function in developing ganglia, which can be correlated wit h the presence of their respective receptors. (C) 1994 John Wiley and Sons, Inc.