10 mm), fixed in methanol-acetone (1:1), washed in phosphate- buffered saline (PBS), blocked in PBS with 30 g/L bovine serum albumin), and incubated overnight at 4uC with the primary antibody in blocking buffer. After washing in PBS with 0.01% (vol/vol) Tween 20, sections were incubated 1 hour at room temperature with Alexa fluor 488 donkey anti-rabbit IgG (Molecular Probes), Cy3 goat anti-mouse IgG (H+L) highly cross-adsorbed, or Cy5 goat anti-chicken IgG (Jackson Laborato- ries) diluted 1/500 in blocking solution. Sections were washed in distilled water and mounted in Vectashield. Immunofluorescence analysis was carried out at the Institut du Fer a` Moulin Cell and Tissue Imaging facility, using a Leica epifluorescence microscope equipped with a CCD camera (Micromax Roper Scientific), or a Leica SP2 confocal laser scanning microscope (Leica, Mannheim, Germany). Acquisition features were kept constant for all acquisitions with the same antibodies. Validation of paranodin immunofluorescence as a diagnostic marker Images from biopsies of CIAP (8) or CIDP (9) immunostained with paranodin antibodies were coded, randomly mixed and examined by 4 unaware observers who were asked to classify them into 3 categories (probable CIAP, probable CIDP, unknown) according to the intensity and extension of paranodin immuno- staining. The proportion of correct identification was determined for each disease. Supporting Information Figure S1 Ultrastructure of a node of Ranvier in superficial peroneal nerve from a CIAP patient. A. Low magnification of a References 1. Suter U, Scherer SS (2003) Disease mechanisms in inherited neuropathies. Nat Rev Neurosci 4: 714–726. 2. McLeod JG, Tuck RR, Pollard JD, Cameron J, Walsh JC (1984) Chronic polyneuropathy of undetermined cause. J Neurol Neurosurg Psychiatry 47: 530–535. 3. Kuitwaard K, van Doorn PA (2009) Newer therapeutic options for chronic inflammatory demyelinating polyradiculoneuropathy. 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Acquired Neuropathies Table S2 CIAP. Found DOCX) longitudinal ultrathin section showing the nodal and paranodal regions. B. Higher magnification of A showing normal perinodal microvilli emanating from the Schwann cells (arrow). C. Higher magnification of A showing paranodal loops with septate-like axoglial junctions (arrowhead). Scale bars: A: 1 mm, B: 0.7 mm and C: 0.5 mm. Found at: doi:10.1371/journal.pone.0014533.s001 (3.82 MB TIF) Table S1 Clinical, paraclinical, and histological characteristics of CIDP patients. Found at: doi:10.1371/journal.pone.0014533.s002 (0.02 MB DOCX) Clinical and histological characteristics of patients with at: doi:10.1371/journal.pone.0014533.s003 (0.02 MB Acknowledgments The authors thank Jean-Paul Rio and Sophie Cyrielle for their help in some experiments, Je´roˆme Devaux and Ekaterina Kordeli for the gift of KCNQ2 and ankyrin G antibodies, respectively, and Andre´ Sobel for his support for immunoblotting experiments. 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