Dual role of the fringe connection gene in both heparan sulphate and fringe-dependent signalling events

The precise regulation of growth factor signalling is crucial to the molecu lar control of development in Drosophila. Post-translational modification o f signalling molecules is one of the mechanisms that modulate developmental signalling specificity. We describe a new gene, fringe connection (frc), t hat encodes a nucleotide-sugar transporter that transfers UDP-glucuronic ac id, UDP-N-acetylglucosamine and possibly UDP-xylose from the cytoplasm into the lumen of the endoplasmic reticulum/Golgi. Embryos with the frc mutatio n display defects in Wingless, Hedgehog and fibroblast growth factor signal ling. Clonal analysis shows that fringe-dependent Notch signalling is disru pted in frc mutant tissue.