Figure 6.

A nesprin isoform switch between immature and mature muscle fibres.

Double-labels of nesprin mAbs with a polyclonal anti-dystrophin to show muscle fibre outlines were counterstained with DAPI to show nuclei. Serial sections. Bars (white) = 100μm

(A, B) In a Becker MD patient, dystrophin staining is weak except in a few revertant fibres. Groups of immature, regenerating fibres are common in Becker MD and their nuclei are more brightly stained for nesprin-1 than surrounding mature fibres (A), but they have less nesprin-2 than surrounding mature fibres (B: white arrows). Immature fibres were identified using a neonatal-specific anti-myosin mAb (NCL-MHCn, Leica, Milton Keynes, UK) on a serial section.

(C, D) In a child with congenital myotonic dystrophy, fibres are smaller with large central nuclei, but dystrophin staining at the sarcolemma is normal. The muscle spindle is a specialized sensory structure in muscle that contains a group of immature muscle fibres (white arrows). These are strongly positive for nesprin-1 (C) but virtually negative for nesprin-2 (D). “N” = nerve, “Cap” = external capsule of the spindle.