Neurofilaments from mammalian central and peripheral nerve share certain polypeptides.

Preparations enriched in mammalian 10 nm frlaments, commonly referred to as neurofilaments have been made from peripheral nerve [I] and brain [Z-S]. Morphologically, isolated filaments from the two sources are indistinguishable and often appear aggregated [l-5] . However, there are considerable discrepancies between the reported polypeptide compositions of brain and peripheral nerve neurofilaments. Three polypeptides with mol. wt 200 000, 1.50 000 and 69 000 have been identi~ed as the major components of peripheral nerve neuro~laments [ I] . Indirect evidence obtained from studies of the slow component of axonal transport has also been used to implicate this same triplet of polypeptides in neurofilament structure [6,7] Preparations of brain 10 nm filaments contain a major polypeptide with a chain wt 50 000-60 000 which has been ascribed the brain neurofilament subunit [3-51, however it was noted that minor higher molecular weight polypeptides are usually present. The possible presence of glial 10 nm filaments in preparations from brain has been recognised for some time [3,8-lo] , however, the degree of any contamination by these filaments is difficult to assess since their constituent protein, glial fibrillary acidic protein, appears to comigrate electrophoretically with the major brain neurofilament polypeptide [4]. We have now directly compared the polypeptide composition of preparations enriched in