HSPG Regulates Trans-Synaptic Signaling Figure 4. Synaptic WNT and BMP ligand abundance is modified by 6-O-S sulfation. Images show muscle 6 NMJ in segment A3 probed in non-detergent conditions, so that only extracellular protein distributions are detected. The white lines indicate cross-section planes for spatial PLOS Genetics | www.plosgenetics.org 9 November 2012 | Volume 8 | Issue 11 | e1003031