Heparan sulphate proteoglycans (HSPGs) – extracellular molecules that bind key secreted morphogens, including Wingless (Wg) and Hedgehog (Hh)– are crucial for normal metazoan development. But pinning down their roles in different signalling pathways can be extremely difficult. For example, it has been recently debated (see Development 131, 2509), whether the fly HSPGs,Dally and Dally-like protein (Dlp), function in both Hh and Wg, or just in Hh,signalling. Now, Franch-Marro et al., on p. 659, conclusively answer this question. By generating dally and dlp null mutant flies, they show that neither Dally nor Dlp is essentially required for embryonic Wg signalling. If wg expression is sustained in double mutant embryos, Wg pathway activation still occurs. By contrast, Dlp has a crucial role in regulating the range of Wg signalling in the wing imaginal discs of developing larvae. The authors report that in the absence of Dlp,short-range Wg signalling in this...

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