Gene expression analyses in X-linked myotubular myopathy

BACKGROUND: X-linked myotubular myopathy (XLMTM) is a severe congenital disorder characterized by marked muscle weakness and hypotonia. Myotubularin, the protein product of the causative gene, MTM1, is thought to be a phosphatase for phosphatidylinositol-3-phosphate and may be involved in membrane trafficking. Analysis of MTM1 knocked-out mice indicates that the characteristic small fibers in XLMTM muscles are due to atrophy rather than hypoplasia. OBJECTIVE: To characterize gene expression profiling of skeletal muscles with XLMTM. METHOD: The authors analyzed the expression of more than 4,200 genes in skeletal muscles from eight patients with XLMTM using their custom cDNA microarray. RESULTS: In XLMTM, gene expression analysis revealed pathognomonic upregulation of transcripts for cytoskeletal and extracellular matrix proteins within or around atrophic myofibers. CONCLUSION: Remodeling of cytoskeletal and extracellular architecture appears to contribute to atrophy and intracellular organelle disorganization in XLMTM myofibers.