Clinical data on DM patients used in this study.

a<p>Medical Research Council, scale for muscle strength; scale (0–5 grade) on 15 muscles at both sides in the upper and lower limbs for a total of 150 maximum score.</p>b<p>Electrocardiogram, included first-degree atrio-ventricular block, incomplete or complete bundle-branch block.</p>c<p>Muscle Impairment Rating Scale, stage of the disease for DM1 patients <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0083777#pone.0083777-Mathieu1" target="_blank">[73]</a>.</p

Metahistograms have been obtained from the analysis of muscle fiber diameters in DM1 patients (A-C) and in DM2 patients (D-F).

<p>The results are based on sections immunostained for MHC fast or slow myosin. Tables show the relative atrophy or hypertrophy factors in each subphenotype considered. Data relative to each DM1 and DM2 phenotypic groups have been obtained by pooling the findings of each patient: DM1-E1 (n = 3), DM1-E2 (n = 5), DM1-CDM (n = 3), DM2-PS (n = 4), DM2-PDM (n = 5) and DM2-PROMM (n = 5).</p

Fast myosin immunostaining of skeletal muscle transversal sections obtained from a healthy patient (A), DM1 patients (B-D) and DM2 patients (E-G).

<p>Type 2 fibers (fast positive fibers) are stained in brown. Muscle from DM1-E1 (B) and DM2-PS (E) patients show a normal histological muscle pattern similar to those observed in control muscle section (A). Muscle from DM1-E2 (C) and DM1-CDM (D) patients show a high fiber size variability with both type 1 (unstained fibers; white arrows) and type 2 (black arrows) atrophic fibers, fast positive nuclear clumps (arrowheads) and a preferential type 1 fiber central nucleation (asterisks). Muscle from DM2-PDM and DM2-PROMM patients also show high fiber size variability with very small type 2 fibers (black arrows), type 2 nuclear clumps (arrowheads) and a preferential type 2 fiber central nucleation (asterisks).</p

Results of QRT-PCR experiments to quantify the expression level of the <i>CLCN1</i> mRNA in biceps brachii muscle samples from DM2 patients (DM2-PS (n = 4), DM2-PDM (n = 5) and DM2-PROMM (n = 5)) and controls.

<p>Each experiment has been performed in triplicate and the relative amount of the <i>CLCN1</i> transcripts has been determined using the β₂-microglobulin as endogenous control gene. Bars represent standard deviation.</p