title: Loss of neural recognition molecule NB-3 delays the normal projection and terminal branching of developing corticospinal tract axons in the mouse.
abstract: Neural recognition molecule NB-3 is involved in neural development and synapse formation. However, its role in axon tract formation is unclear. In this study, we found that the temporal expression of NB-3 in the deep layers of the motor cortex in mice was coincident with the development of the corticospinal tract (CST). Clear NB-3 immunoreactivity in the CST trajectory strongly suggested that NB-3 was expressed specifically in projecting CST axons. By tracing CST axons in NB-3−/− mice at different developmental stages, we found that these axons were capable of projecting and forming a normal trajectory. However, the projection was greatly delayed in NB-3−/− mice compared with wild-type (WT) mice from the embryonic to postnatal stages, a period that is coincident with the completion of the CST projection in mice. Subsequently, although their projection was delayed, CST axons in NB-3−/− mice gradually completed a normal projection. By stage P21, the characteristics of CST projections in NB-3−/− mice were not statistically different from those in WT mice. In addition, we found that the branching of CST axons into spinal gray matter also was delayed in NB-3−/− mice. The CST innervation area in the spinal gray matter of NB-3−/− mice was greatly reduced in comparison with WT mice until P30 and gradually became normal by P45. These data suggest that NB-3 is involved in the normal projection and terminal branching of developing CST axons.
authors.affiliation: State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Zhenhui
authors.initials: Z
authors.lastname: Huang
authors.forename: Yang
authors.initials: Y
authors.lastname: Yu
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Shimoda
authors.forename: Kazutada
authors.initials: K
authors.lastname: Watanabe
authors.forename: Yaobo
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000818:Animals; D015816:Cell Adhesion Molecules, Neuronal / Q000172:deficiency* / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics*; D002678:Chimera; D005260:Female; D020439:Growth Cones / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D061251:Primary Cell Culture; D011712:Pyramidal Tracts / Q000166:cytology / Q000378:metabolism / Q000473:pathology*; D013116:Spinal Cord / Q000166:cytology / Q000473:pathology*
chemical_list: D015816:Cell Adhesion Molecules, Neuronal; C526283:contactin 6 protein, mouse