Ultrastructural perturbations induced by desmin mutants in tibialis anterior muscles. (A) WT, (B to E) R406W desmin, (F to H) E413K desmin; expressing tibialis anterior muscles, 1 week (E) or 1 month (A to D, F to H) after AAV vectors injection. Note that expression of WT desmin does not seem to modify muscle ultrastructure (A), whereas expression of R406W mutant of desmin induces the appearance of granulofilamentous electron-dense material (arrowheads, B to E) located at the perinuclear regions (B to C), between the intermyofibrillar space and at the Z-line (D); and perturbs mitochondria localization (D). Expression of E413K in the tibialis anterior muscle also induces accumulation of granulofilamentous electron-dense material (arrowheads, F to H) that may form ‘ring-like’ structures (asterisk, G). Arrows indicate compressed sarcomere by the accumulation of granulofilamentous electron-dense material. AAV, adeno-associated virus; M, mitochondria; N, nucleus; WT, wild-type.