AGGREGATION OF A SUBPOPULATION OF VIMENTIN FILAMENTS IN CULTURED HUMAN SKIN FIBROBLASTS DERIVED FROM PATIENTS WITH GIANT AXONAL NEUROPATHY

Giant axonal neuropathy (GAN) is a generalized disorder of intermediat e filament networks which results in the formation of an ovoid aggrega te in a large variety of cell types. We investigated the cytoskeletal organization of cultured skin fibroblasts derived from three GAN patie nts by indirect immunofluorescence, confocal, and electron microscopy. Whereas the organization of microfilaments seemed normal, the microtu bule network appeared disorganized and tangled. The organization of th e intermediate filament network, composed of vimentin, was probed with three antibodies directed against different epitopes: two vimentin-sp ecific antibodies, a monoclonal antibody (mAb V9) and a polyclonal ant ibody, and a serum specific for all type III IFPs (PI serum). These ex periments showed that 20% of cultured skin fibroblasts from GAN patien ts have a vimentin aggregate composed of densely packed filaments whic h coexists with a well-organized vimentin network. After depolymerizat ion of microtubules with nocodazole, all fibroblasts from GAN patients contained a vimentin aggregate which seemed to arise from a subpopula tion of vimentin filaments normally integrated in the vimentin network . Such aggregates were never observed in any condition in control fibr oblasts. Moreover, the ultrastructural analysis of GAN cells revealed the presence of swollen mitochondria. We suggest that GAN may be due t o a defect in a factor which stabilizes cytoplasmic intermediate filam ent networks, and we speculate on its identification and properties. ( C) 1996 Wiley-Liss, Inc.