TRKC, A RECEPTOR FOR NEUROTROPHIN-3, IS WIDELY EXPRESSED IN THE DEVELOPING NERVOUS-SYSTEM AND IN NONNEURONAL TISSUES

The Trk family of tyrosine kinases encodes receptors for nerve growth factor-related neurotrophins. Here we present a developmental expressi on study of trkC, which encodes a receptor for neurotrophin-3 (NT-3). Like the related genes, trk and trkB, trkC is expressed primarily in n eural lineages although the pattern is complex and includes non-neuron al cells. Direct comparison with trk and trkB developmental expression patterns permits the following observations. (1) trkC is expressed in novel neural tissues where other Trk genes are silent. (2) Some tissu es appear to coexpress trkB and trkC receptors in the embryo and in th e adult. (3) trkC expression can be detected in the gastrulating embry o. These data provide insights into the role of Trk-family receptors a nd nerve growth factor-related neurotrophins during development and su ggest that, in addition to regulating neuronal survival and differenti ation, the neurotrophin/Trk receptor system may have broader physiolog ical effects. Finally, interspecific mouse backcrosses have been used to map the location of each of the Trk genes on mouse chromosomes. Ali gnment with available chromosomal maps identify possible linkage betwe en the Trk genes and known neurological mutations.