Differential expression of neurofilament triplet proteins in brain development.

Axonal transport studies and biochemical fractionation have led to the concept that the three 'triplet' proteins [approximate molecular weights 200,000 (200K), 145,000 (145K) and 68,000 (68K)] are the essential components of mammalian neurofilaments. Using a correlated biochemical and immunological approach, we have now shown that the 200K protein is under separate developmental control during rat brain differentiation and that the time of its expression differs in different regions. We were unable to detect 200K protein by immunofluorescence or in total brain filament preparations from prenatal rat brain, although the 145K and 68K proteins are both present in an apparently identical distribution. During development, progressively more 145K- and 68K-positive neurofilamentous bundles can be stained with 200K antibodies, paralleling the increasing quantities of this protein detected biochemically in brain filament preparations. We conclude that 200K protein probably has a more specialized role in neurofilament architecture and function than the other two triplet proteins.