title: Ontogenetic expression of trk neurotrophin receptors in the chick auditory system.
abstract: Neurotrophins and their cognate receptors are critical to normal nervous system development. Trk receptors are high-affinity receptors for nerve-growth factor (trkA), brain-derived neurotrophic factor and neurotrophin-4/5 (trkB), and neurotrophin-3 (trkC). We examine the expression of these three neurotrophin tyrosine kinase receptors in the chick auditory system throughout most of development. Trks were localized in the auditory brainstem, the cochlear ganglion, and the basilar papilla of chicks from embryonic (E) day 5 to E21, by using antibodies and standard immunocytochemical methods. TrkB mRNA was localized in brainstem nuclei by in situ hybridization. TrkB and trkC are highly expressed in the embryonic auditory brainstem, and their patterns of expression are both spatially and temporally dynamic. During early brainstem development, trkB and trkC are localized in the neuronal cell bodies and in the surrounding neuropil of nucleus magnocellularis (NM) and nucleus laminaris (NL). During later development, trkC is expressed in the cell bodies of NM and NL, whereas trkB is expressed in the nerve calyces surrounding NM neurons and in the ventral, but not the dorsal, dendrites of NL. In the periphery, trkB and trkC are located in the cochlear ganglion neurons and in peripheral fibers innervating the basilar papilla and synapsing at the base of hair cells. The protracted expression of trks seen in our materials is consistent with the hypothesis that the neurotrophins/tyrosine kinase receptors play one or several roles in the development of auditory circuitry. In particular, the polarized expression of trkB in NL is coincident with refinement of NM terminal arborizations on NL.
authors.affiliation: Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology/Head and Neck Surgery, University of Washington, Seattle 98195-7923, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Cochran
authors.forename: J S
authors.initials: JS
authors.lastname: Stone
authors.forename: O
authors.initials: O
authors.lastname: Bermingham-McDonogh
authors.forename: S R
authors.initials: SR
authors.lastname: Akers
authors.forename: F
authors.initials: F
authors.lastname: Lefcort
authors.forename: E W
authors.initials: EW
authors.lastname: Rubel
mesh_terms: D000818:Animals; D001306:Auditory Pathways / Q000196:embryology* / Q000378:metabolism; D020532:Basal Nucleus of Meynert / Q000196:embryology* / Q000378:metabolism; D001489:Basilar Membrane / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D001933:Brain Stem / Q000196:embryology* / Q000378:metabolism; D002642:Chick Embryo / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D017403:In Situ Hybridization; D009024:Morphogenesis; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D019581:Neuropil / Q000378:metabolism*; D020917:Receptor, trkA / Q000096:biosynthesis* / Q000235:genetics; D020813:Receptor, trkB / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D020812:Receptor, trkC / Q000096:biosynthesis* / Q000235:genetics; D013136:Spiral Ganglion / Q000196:embryology* / Q000378:metabolism
chemical_list: D009419:Nerve Tissue Proteins; D020917:Receptor, trkA; D020813:Receptor, trkB; D020812:Receptor, trkC