Heterophilic binding of L1 on unmyelinated sensory axons mediates Schwann cell adhesion and is required for axonal survival.
This study investigated the function of the adhesion molecule L1 in unmyelinated fibers of the peripheral nervous system (PNS) by analysis of L1- deficient mice. We demonstrate that L1 is present on axons and Schwann cells of sensory unmyelinated fibers, but only on Schwann cells of sympathetic unmyelinated fibers. In L1-deficient sensory nerves, Schwann cells formed but failed to retain normal axonal ensheathment. L1-deficient mice had reduced sensory function and loss of unmyelinated axons, while sympathetic unmyelinated axons appeared normal. In nerve transplant studies, loss of axonal-L1, but not Schwann cell-L1, reproduced the L1-deficient phenotype. These data establish that heterophilic axonal-L1 interactions mediate adhesion between unmyelinated sensory axons and Schwann cells, stabilize the polarization of Schwann cell surface membranes, and mediate a trophic effect that assures axonal survival.
Haney
C A
CA
Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Sahenk
Z
Z
Li
C
C
Lemmon
V P
VP
Roder
J
J
Trapp
B D
BD
D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000648:ultrastructure; D002448:Cell Adhesion; D016764:Cell Polarity; D002470:Cell Survival; D005260:Female; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism; D017353:Gene Deletion; D039841:Leukocyte L1 Antigen Complex; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009186:Myelin Sheath / Q000378:metabolism* / Q000648:ultrastructure; D018992:Myelin-Associated Glycoprotein / Q000235:genetics / Q000378:metabolism; D009410:Nerve Degeneration; D009412:Nerve Fibers / Q000378:metabolism / Q000648:ultrastructure; D019006:Neural Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D009475:Neurons, Afferent / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D017933:Peripheral Nervous System / Q000166:cytology; D011312:Pressure; D012583:Schwann Cells / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D012584:Sciatic Nerve / Q000637:transplantation / Q000648:ultrastructure
D039841:Leukocyte L1 Antigen Complex; D008562:Membrane Glycoproteins; D018992:Myelin-Associated Glycoprotein; D019006:Neural Cell Adhesion Molecules