Oligodendrocytes and Schwann Cells Respond Differently to a Transgene Induced Reduction of Axon Caliber

Abstract

Neurofilaments are the most abundant cytoskeletal elements in the large caliber axons of vertebrate neurons and multiple lines of evidence suggest that they play an important role in establishing axon volume. Each such filament is composed of three different intermediate filament proteins, NFL (60–70 kDa), NFM (150 kDa) and NFH (200 kDa), copolymerized via a common a-helical rod domain (1). Amongst the very large and highly conserved family of intermediate filament proteins, NFM and NFH proteins have exceptionally long carboxy terminal tail domains which form the side-arms at the periphery of each neurofilament. Such projections appear to link neurofilaments and attach neurofilaments to other organelles (2, 3). During neuronal maturation both NFM and NFH become highly phosphorylated in their carboxy domains (4) and this modification is thought to modulate both the strength of inter-neurofilament interactions (5) and the spacing between neurofilaments (6).