Fig. 1. Distribution of axonal proteins is dramatically altered at nodes of Ranvier in the absence of oligodendrocytes. Brain sections from wild-type (A,C,E) and MBP-TK (B,D,F) animals treated from postnatal day 1 to 20 with FIAU were double-labeled with anti-paranodin (PND) (red) and either anti-ankyrin G (green; A,B), anti-Na+ channel (PAN) (green; C,D) or anti-Kv1.1 (green; E,F) antibodies. Wild-type treated mice show a normal localization of paranodin in the paranodal regions (A,C,E) with typical ankyrin G (A) and Na+ channels clusters (C) distribution in the node of Ranvier. In treated MBP-TK mice, paranodin was not detectable in the paranodes, even if the red was enhanced to reveal nonspecific background (B,D,F). Localization of ankyrin G and Na+ channels was also markedly altered and immunoreactivity was mainly found along the axons (arrows in B,D) of treated MBP-TK animals. Double immunostaining for ankyrin G and Na+ channels showed that these proteins are colocalized (Fig. 1D inset). In contrast to the specific distribution of Kv1.1 clusters in the juxtaparanodes in the wild type (E), K+ channel clustering was completely absent after FIAU treatment in MBP-TK mice (F). Pictures represent single optical sections of the corpus callosum region using confocal scanning microscopy. Scale bars: in F, 10 µm in A-F; in inset, 4 µm.
