In vivo trafficking and targeting of N-cadherin to nascent presynaptic terminals.
N-cadherin is a prominent component of developing and mature synapses, yet very little is known about its trafficking within neurons. To investigate N-cadherin dynamics in developing axons, we used in vivo two-photon time-lapse microscopy of N-cadherin--green fluorescent protein (Ncad-GFP), which was expressed in Rohon-Beard neurons of the embryonic zebrafish spinal cord. Ncad-GFP was present as either stable accumulations or highly mobile transport packets. The mobile transport packets were of two types: tubulovesicular structures that moved preferentially in the anterograde direction and discrete-punctate structures that exhibited bidirectional movement. Stable puncta of Ncad-GFP accumulated in the wake of the growth cone with a time course. Colocalization of Ncad-GFP puncta with synaptic markers suggests that N-cadherin is a very early component of nascent synapses. Expression of deletion mutants revealed a potential role of the extracellular domain in appropriate N-cadherin trafficking and targeting. These results are the first to characterize the trafficking of a synaptic cell-adhesion molecule in developing axons in vivo. In addition, we have begun to investigate the cell biology of N-cadherin trafficking and targeting in the context of an intact vertebrate embryo.
Jontes
James D
JD
Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305-5345, USA. jontes@stanford.edu
Emond
Michelle R
MR
Smith
Stephen J
SJ
D000818:Animals; D015820:Cadherins / Q000235:genetics* / Q000378:metabolism*; D002478:Cells, Cultured; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics; D008565:Membrane Proteins / Q000378:metabolism; D008853:Microscopy / Q000379:methods; D016297:Mutagenesis, Site-Directed; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D050683:R-SNARE Proteins; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D013116:Spinal Cord / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D015027:Zebrafish
D015820:Cadherins; D008565:Membrane Proteins; D050683:R-SNARE Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins