title: Dynamic regulation of the expression of neurotrophin receptors by Runx3.
abstract: Sensory neurons in the dorsal root ganglion (DRG) specifically project axons to central and peripheral targets according to their sensory modality. However, the molecular mechanisms that govern sensory neuron differentiation and the axonal projections remain unclear. The Runt-related transcription factors, Runx1 and Runx3, are expressed in DRG neuronal subpopulations, suggesting that they might regulate the cell specification and the trajectories of specific axons. Here, we show that parvalbumin-positive DRG neurons fail to differentiate from the onset in Runx3(-/-) mice. By contrast, TrkC-positive DRG neurons differentiate normally at embryonic day (E) 11.5, but disappear by E13.5 in Runx3(-/-) mice. Subsequently, TrkC-positive DRG neurons reappear but in smaller numbers than in the wild type. In Runx3(-/-) mice, central axons of the TrkC-positive DRG neurons project to the dorsal spinal cord but not to the ventral and intermediate spinal cord, whereas the peripheral axons project to skin but not to muscle. These results suggest that Runx3 controls the acquisition of distinct proprioceptive DRG neuron identities, and that TrkC-positive DRG neurons consist of two subpopulations: Runx3-dependent early-appearing proprioceptive neurons that project to the ventral and intermediate spinal cord and muscle; and Runx3-independent late-appearing cutaneous neurons that project to the dorsal spinal cord and skin. Moreover, we show that the number of TrkA-positive DRG neurons is reduced in Runx3(-/-) mice, as compared with the wild type. These results suggest that Runx3 positively regulates the expression of TrkC and TrkA in DRG neurons.
authors.affiliation: Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan.
authors.forename: Souichiro
authors.initials: S
authors.lastname: Nakamura
authors.forename: Kouji
authors.initials: K
authors.lastname: Senzaki
authors.forename: Masaaki
authors.initials: M
authors.lastname: Yoshikawa
authors.forename: Mika
authors.initials: M
authors.lastname: Nishimura
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Inoue
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Ito
authors.forename: Shigeru
authors.initials: S
authors.lastname: Ozaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Shiga
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D050677:Core Binding Factor Alpha 3 Subunit / Q000235:genetics / Q000502:physiology*; D005727:Ganglia, Spinal / Q000196:embryology / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D051379:Mice; D018345:Mice, Knockout; D009475:Neurons, Afferent / Q000166:cytology / Q000502:physiology*; D010320:Parvalbumins / Q000378:metabolism; D020812:Receptor, trkC / Q000378:metabolism; D017475:Receptors, Nerve Growth Factor / Q000096:biosynthesis*
chemical_list: D050677:Core Binding Factor Alpha 3 Subunit; D010320:Parvalbumins; D017475:Receptors, Nerve Growth Factor; C493730:Runx3 protein, mouse; D020812:Receptor, trkC