THE ONSET OF NEUROTROPHIN AND TRK MESSENGER-RNA EXPRESSION IN EARLY EMBRYONIC-TISSUES OF THE QUAIL

To determine the role of neurotrophins on the initial development of the avian embryo, RT-PCR was used to detect when mRNA for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3), as well as their respective receptors, trkA, trkB, and trkC, is first expressed in the avian embryo. trkA, BDNF, trkB, NT-3, and trkC mRNA were expressed as early as stage 1 (''prestreak'' stage), while NGF mRNA was not expressed until later in development (stage 5, ''notochord'' stage). Microdissection of Embryonic Day 2 quail (stages 12 to 14) and RT-PCR analysis revealed that the neural crest, neural tube, somites, or notochord all expressed some neurotrophin or trk mRNA. Although a neurotrophin and its appropriate receptor were both often present or absent, in several cases they were present individually, suggesting that they might have either local or target-derived actions. (C) 1994 Academic Press, Inc.