Expression of the tyrosine kinase receptor gene trkB is confined to the murine embryonic and adult nervous system

We have examined the expression of the trkB gene, which encodes a member of the family of protein tyrosine kinase (TK) transmembrane receptors, during mouse embryogenesis using in situ hybridization and Northern analysis. Transcripts were first detected in the neuroepithelium and in the neural crest of 9.5 day embryos with regions of high expression in the neural folds and at the lateral neuroepithelium. However, during the process of cephalization and development of the peripheral nervous system, transcripts were detected in most neural tissues, including the brain, spinal cord, cranial and spinal ganglia, and along the pathways of axonal tracts extending peripherally. In the adult brain, expression continues in a complex pattern that is confined to specific regions or neuron types. The expression of trkB, a TK receptor, in early embryogenesis, and specifically in neural tissues, is consistent with the notion that this gene plays a role in the events that regulate the development of the nervous system.