Restricted expression of N- and R-cadherin on neurites of the developing chicken CNS.
The expression of two cadherins, N- and R-cadherin, was mapped in the CNS of chicken embryos of 6-11 d incubation, focusing on the sensory and motor fiber systems. In the spinal cord, the laterally located fibers of the dorsal funiculus express N-cadherin while the medially located fibers do not. These two fiber systems have a different course within the CNS but associate to form the spinal dorsal roots. In the hindbrain, N-cadherin is expressed by the descending trigeminal (general somatic sensory) tract, which is contiguous with the N-cadherin-positive zone of the dorsal funiculus of the spinal cord. R-cadherin is not expressed by sensory fibers, but is expressed by the visceral motor system of the vagus and glossopharyngeal nerves, which are N-cadherin negative. The motor neurites expressing R-cadherin have a different course within the brain than the sensory neurites expressing N-cadherin, although they form the common sensory/motor roots of the vagus nerve at the surface of the brain. The possibility that N-cadherin provides a guidance cue for sensory axon migration within the CNS by a homophilic adhesion mechanism was investigated in vitro. Explants from sensory spinal ganglia expressing N-cadherin were placed on N-cadherin-transfected neuroblastoma cells, and axon outgrowth was visualized. Results showed that the sensory axons defasciculate and closely follow the cell-cell boundaries between transfected cells where high levels of N-cadherin are expressed. These results show that the two cadherins, like members of the immunoglobulin superfamily of molecules, are expressed in a topographically restricted fashion during chick brain development. They furthermore suggest that N-cadherin expression by neurites may play a role in guiding these neurites along CNS paths that express the same molecule.
Redies
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Department of Biophysics, Faculty of Science, Kyoto University, Japan.
Inuzuka
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Takeichi
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D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology; D015820:Cadherins / Q000378:metabolism*; D002232:Carbocyanines; D002490:Central Nervous System / Q000378:metabolism*; D002642:Chick Embryo; D005456:Fluorescent Dyes; D016501:Neurites / Q000378:metabolism*; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology; D012249:Rhombencephalon / Q000378:metabolism; D013116:Spinal Cord / Q000378:metabolism
D015820:Cadherins; D002232:Carbocyanines; D005456:Fluorescent Dyes; C024286:3,3'-dioctadecylindocarbocyanine