title: Genetic evidence for selective neurotrophin 3 signalling through TrkC but not TrkB in vivo.
abstract: Neurotrophins control neuronal survival in a target-derived manner during the period of naturally occurring cell death in development. The specificity of this mechanism has been attributed to a restricted spatio-temporal expression of neurotrophin ligands in target tissues, as well as a selective expression of their cognate tyrosine kinase (Trk) receptors in different neuronal subpopulations. However, several in vitro and in vivo studies of null mutant mice have suggested that neurotrophin 3 (NT 3) also signals through the non-preferred TrkB receptor. In this study, we have directly addressed the in vivo preference of NT 3 to signal through TrkB or TrkC, by crossing the NT 3 knock-in mice (BDNF(NT 3/NT 3) mice) with the TrkB- or TrkC-null mutant mice. We find that TrkB is dispensable, whereas TrkC is required for the neuronal rescue by the NT 3 allele in the brain-derived neurotrophic factor- and NT 3-dependent cochleovestibular system. Our results show that NT 3 maintains survival of cells as well as target innervation only through interactions with TrkC in vivo. TrkB and TrkC receptors are thus not functionally redundant for NT 3, even when coexpressed in neurons of the cochleovestibular system.
authors.affiliation: Unit of Molecular Neurobiology, MBB, Karolinska Institutet,Stockholm, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Stenqvist
authors.forename: Karin
authors.initials: K
authors.lastname: Agerman
authors.forename: Frédéric
authors.initials: F
authors.lastname: Marmigère
authors.forename: Liliana
authors.initials: L
authors.lastname: Minichiello
authors.forename: Patrik
authors.initials: P
authors.lastname: Ernfors
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000235:genetics / Q000378:metabolism; D017950:Ganglia, Sensory / Q000502:physiology; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D018862:Merkel Cells; D051379:Mice; D008817:Mice, Mutant Strains; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D020933:Neurotrophin 3 / Q000235:genetics / Q000502:physiology*; D016133:Polymerase Chain Reaction; D020813:Receptor, trkB / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020812:Receptor, trkC / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D019208:Brain-Derived Neurotrophic Factor; D020933:Neurotrophin 3; D020813:Receptor, trkB; D020812:Receptor, trkC