Wnt, Hedgehog and junctional Armadillo/beta-catenin establish planar polarity in the Drosophila embryo.
To generate specialized structures, cells must obtain positional and directional information. In multi-cellular organisms, cells use the non-canonical Wnt or planar cell polarity (PCP) signaling pathway to establish directionality within a cell. In vertebrates, several Wnt molecules have been proposed as permissible polarity signals, but none has been shown to provide a directional cue. While PCP signaling components are conserved from human to fly, no PCP ligands have been reported in Drosophila. Here we report that in the epidermis of the Drosophila embryo two signaling molecules, Hedgehog (Hh) and Wingless (Wg or Wnt1), provide directional cues that induce the proper orientation of Actin-rich structures in the larval cuticle. We further find that proper polarity in the late embryo also involves the asymmetric distribution and phosphorylation of Armadillo (Arm or beta-catenin) at the membrane and that interference with this Arm phosphorylation leads to polarity defects. Our results suggest new roles for Hh and Wg as instructive polarizing cues that help establish directionality within a cell sheet, and a new polarity-signaling role for the membrane fraction of the oncoprotein Arm.
Colosimo
Pamela F
PF
Program in Developmental Biology, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America.
Tolwinski
Nicholas S
NS
D000818:Animals; D030801:Animals, Genetically Modified; D051186:Armadillo Domain Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D019521:Body Patterning; D016764:Cell Polarity; D017931:DNA Primers / Q000235:genetics; D004330:Drosophila / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D017344:Genes, Insect; D005838:Genotype; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D010641:Phenotype; D010766:Phosphorylation; D015398:Signal Transduction; D014018:Tissue Distribution; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D051155:Wnt1 Protein / Q000235:genetics / Q000378:metabolism*
C495305:ARM protein, Drosophila; D051186:Armadillo Domain Proteins; D017931:DNA Primers; D029721:Drosophila Proteins; D053823:Hedgehog Proteins; D014157:Transcription Factors; D051155:Wnt1 Protein; C074622:wg protein, Drosophila; C077245:hh protein, Drosophila