C. elegans MOM-5/frizzled functions in MOM-2/Wnt-independent cell polarity and is localized asymmetrically prior to cell division.
C. elegans embryonic cells have a common anterior/posterior (a/p) polarity that is apparent in the localization of the transcription factor POP-1. The level of nuclear POP-1 remains high in the anterior daughters of dividing cells but is lowered in the posterior daughters. To generate POP-1 asymmetry, most early embryonic cells require contact with signaling cells that express the ligand MOM-2/Wnt; the point of cell contact specifies the daughter with low nuclear POP-1. In contrast, slightly older embryonic cells that have no apparent prior exposure to Wnt signaling can generate POP-1 asymmetry, provided these cells express MOM-5/Frizzled. We show here that MOM-5::GFP is enriched at the posterior pole of cells prior to division and that a similar asymmetry is observed in cultured cells with no apparent prior exposure to Wnt signaling. While depleting these latter cells of MOM-5/Frizzled causes both daughter cells to have high levels of POP-1, we show that both daughter cells have low levels of POP-1 in embryos with atypically high levels of MOM-5::GFP. These results suggest that MOM-5/Frizzled asymmetry leads to POP-1 asymmetry. In later embryogenesis, we find that MOM-5::GFP localizes to the leading edges of epidermal cells during ventral enclosure. These localization patterns suggest a parallel between MOM-5/Frizzled and the roles of Drosophila Frizzled in planar polarity and dorsal enclosure.
Park
Frederick D
FD
Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
Tenlen
Jennifer R
JR
Priess
James R
JR
D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000254:growth & development; D029742:Caenorhabditis elegans Proteins / Q000502:physiology*; D002453:Cell Cycle / Q000502:physiology*; D016764:Cell Polarity / Q000502:physiology*; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000502:physiology; D049452:Green Fluorescent Proteins; D006609:High Mobility Group Proteins / Q000502:physiology; D036341:Intercellular Signaling Peptides and Proteins / Q000502:physiology; D008565:Membrane Proteins / Q000502:physiology*; D018613:Microscopy, Confocal; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D051153:Wnt Proteins
D029742:Caenorhabditis elegans Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C108315:Mom-5 protein, C elegans; D051153:Wnt Proteins; C096787:pop-1 protein, C elegans; D049452:Green Fluorescent Proteins