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First published online 31 January 2007
doi: 10.1242/dev.02776
1 Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235,
USA.
2 Department of Medicine, Vanderbilt University Medical School, Nashville, TN
37232, USA.
3 Nephrology Division, Harvard Medical School, Massachusetts General Hospital,
Charlestown, MA 02129, USA.
* Author for correspondence (e-mail: lilianna.solnica-krezel{at}vanderbilt.edu)
Accepted 6 December 2006
Human ARHGEF11, a PDZ-domain-containing Rho guanine nucleotide exchange
factor (RhoGEF), has been studied primarily in tissue culture, where it
exhibits transforming ability, associates with and modulates the actin
cytoskeleton, regulates neurite outgrowth, and mediates activation of Rho in
response to stimulation by activated G
12/13 or Plexin B1. The fruit fly
homolog, RhoGEF2, interacts with heterotrimeric G protein subunits to activate
Rho, associates with microtubules, and is required during gastrulation for
cell shape changes that mediate epithelial folding. Here, we report functional
characterization of a zebrafish homolog of ARHGEF11 that is expressed
ubiquitously at blastula and gastrula stages and is enriched in neural tissues
and the pronephros during later embryogenesis. Similar to its human homolog,
zebrafish Arhgef11 stimulated actin stress fiber formation in cultured cells,
whereas overexpression in the embryo of either the zebrafish or human protein
impaired gastrulation movements. Loss-of-function experiments utilizing a
chromosomal deletion that encompasses the arhgef11 locus, and
antisense morpholino oligonucleotides designed to block either translation or
splicing, produced embryos with ventrally-curved axes and a number of other
phenotypes associated with ciliated epithelia. Arhgef11-deficient embryos
often exhibited altered expression of laterality markers, enlarged brain
ventricles, kidney cysts, and an excess number of otoliths in the otic
vesicles. Although cilia formed and were motile in these embryos, polarized
distribution of F-actin and Na+/K+-ATPase in the
pronephric ducts was disturbed. Our studies in zebrafish embryos have
identified new, essential roles for this RhoGEF in ciliated epithelia during
vertebrate development.
Key words: Pronephros, Left-right asymmetry, Otoliths, PDZ-RhoGEF, Arhgef11, Cell polarity, Zebrafish
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