ABNORMAL EXPRESSION OF INTERMEDIATE FILAMENT PROTEINS IN X-LINKED MYOTUBULAR MYOPATHY IS NOT REPRODUCED IN-VITRO

Expression patterns of the intermediate filament proteins (IFPs) desmi n and vimentin, in biopsy material taken from a 1 day old boy with fat al neonatal X-linked myotubular myopathy (XLMTM) were compared with th e expression of these proteins in cultured myotubes, from the same pat ient. Immunohistochemical studies revealed the persistence of high lev els of desmin in virtually all, and vimentin in most, of the myofibres within the patient's biopsy. Analysis of intermediate filament expres sion in differentiating cultured muscle cells did not reveal overt dif ferences between XLMTM cultures and cultures of control muscle. Titin distribution patterns indicated a normal process of myofibrillogenesis in XLMTM myotubes. We conclude that the failure to properly regulate IFP-expression is not intrinsic to XLMTM muscle fibres. The possibilit y that this failure is due to a defective external, possibly neural fa ctor, is discussed.