R. Williams et al., DEVELOPMENTALLY-REGULATED EXPRESSION OF MESSENGER-RNA FOR NEUROTROPHIN HIGH-AFFINITY (TRK) RECEPTORS WITHIN CHICK TRIGEMINAL SENSORY NEURONS, European journal of neuroscience, 7(1), 1995, pp. 116-128
To investigate the distribution of neurons within the developing trige
minal sensory system which express mRNA for each of the three known hi
gh-affinity neurotrophin receptors (trk, trkB and trkC), we have perfo
rmed in situ hybridization histochemistry on serial sections through t
he trigeminal ganglion and trigeminal mesencephalic nucleus at various
ages of development using specific antisense oligonucleotide probes.
We show that trkC mRNA is first expressed in the chicken embryo at sta
ge 13, in presumptive neurons prior to the formation of the ganglion,
that trkB mRNA labelling is initially observed within peripheral neuro
ns slightly later, at stage 19, and that trk mRNA expression is not de
tectable until around embryonic day 3.5 (Istage 21/22). The neurons wh
ich exhibit mRNA labelling for each of the high-affinity receptors occ
upy discrete regions within the ganglion, indicating that the ganglion
comprises distinct neuronal subpopulations, each of which has a diffe
rent capacity to respond to the different neurotrophins. Neurons which
express trk mRNA are confined to the proximal region of the ganglion,
whereas those which express trkB mRNA and trkC mRNA are located in tw
o distinct regions within the distal aspect and also within the trigem
inal mesencephalic nucleus. From the estimation of the number of neuro
ns which exhibit labelling between embryonic days 9 and 18, we determi
ned that the expression of mRNA for the high-affinity receptors change
s during embryonic development of the ganglion. This is consistent wit
h the observed differences in the response to neurotrophins in vitro.