Abstract
BackgroundDistal myopathy with rimmed vacuoles/hereditary inclusion body myopathy is clinically characterized by the early involvement of distal leg muscles. The striking pathological features of the myopathy are muscle fibers with rimmed vacuoles. To date, the role of aquaporin-4 water channel in distal myopathy with rimmed vacuoles/hereditary inclusion body myopathy has not been studied.Case presentationHere, we studied the expression of aquaporin-4 in muscle fibers of a patient with distal myopathy with rimmed vacuoles/hereditary inclusion body myopathy. Immunohistochemical and immunofluorescence analyses showed that sarcolemmal aquaporin-4 immunoreactivity was reduced in many muscle fibers of the patient. However, the intensity of aquaporin-4 staining was markedly increased at rimmed vacuoles or its surrounding areas and in some muscle fibers. The fast-twitch type 2 fibers were predominantly involved with the strong aquaporin-4-positive rimmed vacuoles and TAR-DNA-binding protein-43 aggregations. Rimmed vacuoles with strong aquaporin-4 expression seen in the distal myopathy with rimmed vacuoles/hereditary inclusion body myopathy patient were not found in control muscles without evidence of neuromuscular disorders and the other disease-controls.ConclusionsAquaporin-4 might be crucial in determining the survival or degeneration of fast-twitch type 2 fibers in distal myopathy with rimmed vacuoles/hereditary inclusion body myopathy.
Highlights
Distal myopathy with rimmed vacuoles/hereditary inclusion body myopathy is clinically characterized by the early involvement of distal leg muscles
Aquaporin-4 might be crucial in determining the survival or degeneration of fast-twitch type 2 fibers in distal myopathy with rimmed vacuoles/hereditary inclusion body myopathy
We investigated accumulation of TAR-DNA-binding protein-43 (TDP-43), a pathological hallmark of vacuolar myopathies [11,12], in the muscle fibers of distal myopathy with rimmed vacuoles (DMRV)/hIBM patients
Summary
Distal myopathy with rimmed vacuoles/hereditary inclusion body myopathy is clinically characterized by the early involvement of distal leg muscles. Case presentation: Here, we studied the expression of aquaporin-4 in muscle fibers of a patient with distal myopathy with rimmed vacuoles/hereditary inclusion body myopathy. Autosomal recessive distal myopathy with rimmed vacuoles (DMRV)/hereditary inclusion body myopathy (hIBM) is clinically characterized by preferential involvement of the distal leg muscles in the very early stage, and later of most proximal muscles. DMRV/hIBM is caused by a mutation in the uridine diphosphate-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene, which encodes a bifunctional enzyme catalyzing the 2 exclusive rate-limiting reactions of sialic acid synthesis in the cytosol [3,4] Why these mutations produce a myopathy with RVs remains to be determined. We investigated accumulation of TAR-DNA-binding protein-43 (TDP-43), a pathological hallmark of vacuolar myopathies [11,12], in the muscle fibers of DMRV/hIBM patients
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