Research article summary (published 13 Dec 2001):

Synapse-forming axons and recombinant agrin induce microprocess formation on myotubes.

Full Abstract

We examined cell-surface behavior at nerve-muscle contacts during synaptogenesis in cocultures of rat ventral spinal cord (VSC) neurons and myotubes. Developing synapses in 1-d-old cocultures were identified by the presence of axon-induced acetylcholine receptor (AChR) aggregation. Identified regions were then examined by transmission and scanning electron microscopy. The myotube surface near contacts with axons that induced AChR aggregation typically displayed ruffles, microvilli, and filopodia (microprocesses), indicating motility of the myotube surface. At some of these contact sites microprocesses were wrapped around the axon, resulting in the partial or total "submersion" of the axon within the myotube contours. Sites of myotube contact with somata and dendrites of the same neurons showed much less evidence of motility and surface interaction than sites of contact with axons. Moreover, the distance between opposed membranes of axons and myotubes was smaller than between dendrites or somata and myotubes, suggesting stronger adhesion of axons. These results suggest polarized expression of molecules involved in the induction of microprocess formation and adhesion in developing VSC neurons. We therefore tested the ability of agrin, which is preferentially secreted by axons, to induce microprocess formation in myotubes. Addition of recombinant C-terminal agrin to culture medium resulted in formation of microprocesses within 3 hr. Myotubes transfected with full-length rat agrin constructs displayed numerous filopodia, as revealed by fluorescence microscopy. The results suggest that the induction of muscle cell surface motility may be linked to the signaling processes that trigger the initial formation of the neuromuscular junction.

Author information

Author/s: Uhm, C S (CS); Neuhuber, B (B); Lowe, B (B); Crocker, V (V); Daniels, M P (MP);

Affiliation: Laboratory of Biochemical Genetics, National Heart, Lung, and Blood Institute, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-4036, USA.

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: The Journal of neuroscience : the official journal of the Society for Neuroscience (J Neurosci), published in United States. (Language: eng)

Reference: 2001-Dec; vol 21 (issue 24) : pp 9678-89

Dates: Created 2001/12/12; Completed 2002/01/23; Revised 2006/11/15;

PMID: 11739577, status: MEDLINE (last retrieval date: 2/18/2009, IMS Date: )

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Agrin - biosynthesis; genetics; pharmacology Animals Axons - physiology; ultrastructure Cell Surface Extensions - drug effects; ultrastructure Cells, Cultured Coculture Techniques Dendrites - physiology; ultrastructure Epidermal Growth Factor - pharmacology Green Fluorescent Proteins Growth Cones - physiology; ultrastructure Luminescent Proteins - genetics Microscopy, Electron

Microscopy, Fluorescence Muscle, Skeletal - drug effects; embryology; metabolism; ultrastructure Neuromuscular Junction - drug effects; metabolism; ultrastructure Neurons - drug effects; metabolism; ultrastructure Pseudopodia - drug effects; ultrastructure Rats Receptor Aggregation - physiology Receptors, Cholinergic - metabolism Recombinant Fusion Proteins - biosynthesis; genetics; pharmacology Signal Transduction Synapses - physiology; ultrastructure Transfection

Associated Chemicals: Agrin (0) ; Luminescent Proteins (0) ; Receptors, Cholinergic (0) ; Recombinant Fusion Proteins (0) ; Green Fluorescent Proteins (147336-22-9) ; Epidermal Growth Factor (62229-50-9)

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