ACT-5 is an essential Caenorhabditis elegans actin required for intestinal microvilli formation.
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. Green fluorescent protein reporter and immunofluorescence 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 looked 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. Together with immuno-electron microscopy experiments that indicated ACT-5 is enriched within microvilli themselves, these results suggest a microvillus-specific function for act-5, and further, they raise the possibility that specific actins may be specialized for building microvilli and related structures.
MacQueen
A J
AJ
Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Baggett
J J
JJ
Perumov
N
N
Bauer
R A
RA
Januszewski
T
T
Schriefer
L
L
Waddle
J A
JA
D000199:Actins / Q000737:chemistry / Q000502:physiology*; D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D017353:Gene Deletion; D005786:Gene Expression Regulation; D005838:Genotype; D006579:Heterozygote; D006720:Homozygote; D007413:Intestinal Mucosa / Q000378:metabolism*; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008871:Microvilli / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D017386:Sequence Homology, Amino Acid; D013997:Time Factors
C505596:ACT-5 protein, C elegans; D000199:Actins; D029742:Caenorhabditis elegans Proteins; D020033:Protein Isoforms