Blood enters the glomerular capillaries and is filtered across the endothelium and the basement membrane and through the filtration slits between podocyte foot processes to produce the primary urinary filtrate. In healthy glomeruli, this barrier restricts the passage of macromolecules but is highly permeable to water and small solutes. In this issue of the JCI, Galeano et al. (1) show that a mutation (M712T) in Gne/Mnk in mice results in a reduction in the number of sialic acid residues on critical glomerular proteins such as PC that are found on the apical surface of podocytes. Loss of sialylated proteins is associated with foot process fusion or collapse, splitting of the glomerular basement membrane (GBM), and loss of rbc and proteins such as albumin into the urine. Dietary supplementation with ManNAc prolongs life in mutant Gne^M712T/M712T mice and improves ultrastructure of the glomerular filtration barrier.