In the Drosophila FXS model, the GPI-anchored heparan sulfate proteoglycan (HSPG) glypican Dally-like protein (Dlp) acting as a Wg co-receptor, as well as the transmembrane HSPG syndecan (Sdc), are both highly elevated at the NMJ synaptic terminal (Friedman et al., 2013). Here, TXNL4B is linked to fragile X syndrome.