Glypicans shunt the Wingless signal between local signalling and further transport.
The two glypicans Dally and Dally-like have been implicated in modulating the activity of Wingless, a member of the Wnt family of secreted glycoprotein. So far, the lack of null mutants has prevented a rigorous assessment of their roles. We have created a small deletion in the two loci. Our analysis of single and double mutant embryos suggests that both glypicans participate in normal Wingless function, although embryos lacking maternal and zygotic activity of both genes are still capable of transducing the signal from overexpressed Wingless. Genetic analysis of dally-like in wing imaginal discs leads us to a model whereby, at the surface of any given cell of the epithelium, Dally-like captures Wingless but instead of presenting it to signalling receptors expressed in this cell, it passes it on to neighbouring cells, either for paracrine signalling or for further transport. In the absence of dally-like, short-range signalling is increased at the expense of long-range signalling (reported by the expression of the target gene distalless) while the reverse is caused by Dally-like overexpression. Thus, Dally-like act as a gatekeeper, ensuring the sharing of Wingless among cells along the dorsoventral axis. Our analysis suggests that the other glypican, Dally, could act as a classical co-receptor.
Franch-Marro
Xavier
X
National Institute for Medical Research, The Ridgeway Mill Hill, London NW7 1AA, UK. jp.vincent@nimr.mrc.ac.uk
Marchand
Oriane
O
Piddini
Eugenia
E
Ricardo
Sara
S
Alexandre
Cyrille
C
Vincent
Jean-Paul
JP
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D019521:Body Patterning / Q000502:physiology; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000196:embryology / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D011509:Proteoglycans / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D014921:Wings, Animal / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D051155:Wnt1 Protein
D029721:Drosophila Proteins; D008562:Membrane Glycoproteins; D011509:Proteoglycans; D011518:Proto-Oncogene Proteins; D051155:Wnt1 Protein; C098128:dally protein, Drosophila; C420997:dlp protein, Drosophila; C074622:wg protein, Drosophila