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© The Rockefeller University Press,
0021-9525/2000//931 $5.00
The Journal of Cell Biology, Volume 149, Number 4,
, 2000 931-942
Original Article |
Mutations in β-Spectrin Disrupt Axon Outgrowth and Sarcomere Structure
jorgensen{at}biology.utah.edu
β-Spectrin is a major component of the membrane skeleton, a structure found at the plasma membrane of most animal cells. β-Spectrin and the membrane skeleton have been proposed to stabilize cell membranes, generate cell polarity, or localize specific membrane proteins. We demonstrate that the Caenorhabditis elegans homologue of β-spectrin is encoded by the unc-70 gene. unc-70 null mutants develop slowly, and the adults are paralyzed and dumpy. However, the membrane integrity is not impaired in unc-70 animals, nor is cell polarity affected. Thus, β-spectrin is not essential for general membrane integrity or for cell polarity. However, β-spectrin is required for a subset of processes at cell membranes. In neurons, the loss of β-spectrin leads to abnormal axon outgrowth. In muscles, a loss of β-spectrin leads to disorganization of the myofilament lattice, discontinuities in the dense bodies, and a reduction or loss of the sarcoplasmic reticulum. These defects are consistent with β-spectrin function in anchoring proteins at cell membranes.
Key Words: unc-70 • Caenorhabditis elegans • cytoskeleton • neurons • muscles
© 2000 The Rockefeller University Press
Abbreviations used in this paper: GFP, green fluorescent protein; ORF, open reading frame; PH, pleckstrin homology.
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