Endogenous PRG3 is located in neurites and growth cones of primary hippocampal neurons after DIV 4. (A) Confocal images of a typical extension of a hippocampal neuron at DIV 4, stained with anti-PRG3 296 (green, left) and anti-α-tubulin (red, middle). An overlay (right) shows that native PRG3 is found in all neurites, regardless of their fate. (B) Confocal images of a representative hippocampal neuron stained with anti-PRG3 296 (green) and anti-β-actin (red) showing that PRG3 is present in high amounts at the onset of the neurite, but only in a very small amount at the growth cone, which stained strongly for β-actin. (C) Confocal images of a hippocampal neuron stained with anti-PRG3 296 and anti-tau1 antibodies, and (D) a neuron stained with anti-PRG3 296 and anti-MAP2 show similar distribution of PRG3 at the neurite shaft, irrespective of the underlying structure. Scale bars: 10 μm.