Zebrafish Rho kinase 2 acts downstream of Wnt11 to mediate cell polarity and effective convergence and extension movements.
BACKGROUND
During vertebrate gastrulation convergence and extension (CE), movements narrow and lengthen embryonic tissues. In Xenopus and zebrafish, a noncanonical Wnt signaling pathway constitutes the vertebrate counterpart to the Drosophila planar cell polarity pathway and regulates mediolateral cell polarization underlying CE. Despite the identification of several signaling molecules required for normal CE, the downstream transducers regulating individual cell behaviors driving CE are only beginning to be elucidated. Moreover, how defective mediolateral cell polarity impacts CE is not understood.


RESULTS
Here, we show that overexpression of zebrafish dominant-negative Rho kinase 2 (dnRok2) disrupts CE without altering cell fates, phenocopying noncanonical Wnt signaling mutants. Moreover, Rho kinase 2 (Rok2) overexpression partially suppresses the slb/wnt11 gastrulation phenotype, and ectopic expression of noncanonical Wnts modulates Rok2 intracellular distribution. In addition, time-lapse analyses associate defective dorsal convergence movements with impaired cell elongation, mediolateral orientation, and consequently failure to migrate along straight paths. Transplantation experiments reveal that dnRok2 cells in wild-type hosts neither elongate nor orient their axes. In contrast, wild-type cells are able to elongate their cell bodies in dnRok2 hosts, even though they fail to orient their axes.


CONCLUSIONS
During zebrafish gastrulation, Rok2 acts downstream of noncanonical Wnt11 signaling to mediate mediolateral cell elongation required for dorsal cell movement along straight paths. Furthermore, elongation and orientation of the cell body are independent properties that require both cell-autonomous and nonautonomous Rok2 function.
Marlow
Florence
F
Department of Biological Sciences, Vanderbilt University, VU Station B 351634, Nashville, TN 37235-1634, USA.
Topczewski
Jacek
J
Sepich
Diane
D
Solnica-Krezel
Lilianna
L
D000818:Animals; D001483:Base Sequence; D019070:Cell Lineage; D016764:Cell Polarity / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000166:cytology; D047108:Embryonic Development; D006023:Glycoproteins / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins; D009841:Oligonucleotides; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D015398:Signal Transduction; D051153:Wnt Proteins; D029867:Xenopus Proteins; D015027:Zebrafish / Q000196:embryology; D029961:Zebrafish Proteins; D054460:rho-Associated Kinases
D006023:Glycoproteins; D047908:Intracellular Signaling Peptides and Proteins; D009841:Oligonucleotides; D051153:Wnt Proteins; C092568:Wnt11 protein, zebrafish; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; C512785:wnt11b protein, Xenopus; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases