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A more recent version of this article appeared on July 1, 2005
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Submitted on December 10, 2004
Revised on March 30, 2005
Accepted on April 25, 2005
*Molecular Biology Department and
Molecular and Cellular Imaging Facility, University of Texas Southwestern Medical Center, Dallas, TX 75390; ||Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110
Monitoring Editor: Susan Strome
Investigation of Caenorhabditis elegans act-5 gene function revealed that intestinal microvillus formation requires a specific actin isoform. ACT-5 is the most diverged of the five C. elegans actins, sharing only 93% identity with the other four. GFP reporter and immunofluoresence analysis indicated that act-5 gene expression is limited to microvillus -containing cells within the intestine and excretory systems, and that ACT-5 is apically localized within intestinal cells. Animals heterozygous for a dominant act-5 mutation appeared clear and thin, and grew slowly. Animals homozygous for either the dominant act-5 mutation, or a recessive loss of function mutant, exhibited normal morphology and intestinal cell polarity, but died during the first larval stage. Ultrastructural analysis revealed a complete loss of intestinal microvilli in homozygous act-5 mutants. Forced expression of ACT-1 under the control of the act-5 promoter did not rescue the lethality of the act-5 mutant. Taken together with immuno-EM experiments that indicated ACT-5 is enriched within microvilli themselves, these results suggest a microvillus - specific function for act-5 and, further, raise the possibility that specific actins may be specialized for building microvilli and related structures.
Molecular, Cellular and Developmental Biology Department, Yale University, New Haven, CT 06511;
Biology Department, Southern Methodist University, Dallas, TX 75275.
J. A. Waddle (jwaddle{at}mail.smu.edu)
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