Expression of nerve growth factor receptor mRNA during early development of the chicken embryo: emphasis on cranial ganglia

In situ hybridization with beta-nerve growth factor receptor (NGF-R) oligonucleotide probes was used to study NGF-R mRNA expression in early chicken embryos. Sections through the region of the visceral arches showed high levels of NGF-R mRNA in mesenchyme of the visceral arches, neural tube and myotomes. Labelling was also seen over E3 primordium of the trigeminal ganglion (V) and in the placodal thickening of the petrosal (IX) and nodose (X) ganglionic primordia. In the E5 embryo, all cranial sensory ganglia (V, VII, VIII, IX, X) expressed NGF-R mRNA although at varying levels with higher levels in the ganglia of the Vth, IXth and Xth cranial nerves than in ganglia of the VIIth and the VIIIth nerves. Within ganglia of the Vth, IXth and Xth cranial nerves, levels of NGF-R mRNA were higher in regions containing placode-derived neurons, than in regions with neural-crest-derived neurons. The placode-derived nodose ganglion (X) expressed NGF-R mRNA at all stages of development. In the E15 embryo and later in development, two thirds of the large neuron-like cells expressed high levels of NGF-R mRNA. Our results show that expression of NGF-R mRNA, in peripheral neurons, is not restricted to cells of neural crest origin. We also show a transient expression of NGF-R mRNA early in development in a wide range of non-neuronal differentiating cells. The high level of NGF-R mRNA in early differentiating tissues suggest that the NGF-R plays a wider role during development than previously anticipated.