Fig. 2. All three EXT genes are involved in HSPG biosynthesis in vivo. HSPG levels at the lateral surface of cells in the wild-type and mutant wing imaginal discs. (A) In the wild-type disc, uniform staining is detected (gray on the left panel). (B-D) Clones of cells mutant for the EXT genes are marked by the absence of GFP (green on the right panel). HSPG levels are severely reduced in cells mutant for any of the EXT genes. Here, and on all Figures in this report, imaginal discs are oriented anterior to the left and dorsal to the bottom.