F-spondin protein accumulates in peripheral nerve and adjacent mesenchyme. A, E15 rat peripheral nerve immunolabeled with the R5 antibody (FITC). B, The same section as A immunolabeled with the HNK-1 mAb (TRITC).C, Overlap of R5 (FITC) and HNK-1 (TRITC). F-spondin protein is colocalized with HNK-1 within the nerve and is also detected around it.