Microheterogeneity (``Neurotypy'') of Neurofilament Proteins

Neurofilaments purified from adult rat brainstem by two methods were electrophoresed on NaDodSO4/polyacrylamide gels to separate the triplet proteins (approximate Mrs of 200,000, 155,000, and 68,000) which, in turn, were electroblotted onto nitrocellulose paper. On Coomassie blue-stained gels that were not electroblotted, the same banding pattern was seen with both methods of preparation. Immunocytochemical staining of the electroblots with each of five monoclonal antibodies revealed that three of the monoclonal antibodies were specific for the Mr200,000 neurofilament protein and two, for both the Mrs 200,000 and 155,000 neurofilament proteins. None of the antibodies reacted with the Mr68,000 band. The Mr200,000 band could be resolved into doublet bands. Individual monoclonal antibodies reacted with either one or both of the Mr200,000 doublets. The immunocytochemical staining of the neurofilament triplets on electroblots was compared to that of adult rat cerebellar paraffin sections. Each monoclonal antibody had a unique pattern of staining, reacting only with certain subpopulations of neurons or their processes. Correlation of the staining patterns in cerebellar tissue sections with those of neurofilament polypeptides on electroblots suggested that different neurofilament polypeptides can be localized to different structures and subpopulations of neurons and that molecular heterogeneity (``neurotypy'') may be revealed within the Mrs 200,000 and 155,000 neurofilament polypeptides.