Rat and mouse monoclonal antibodies to human myelin basic protein

Down-regulation of GAP-43 During Oligodendrocyte Development and Lack of Expression by Astrocytes In Vivo: Implications for Macroglial Differentiation

The discovery of molecular markers which are selectively expressed during the development of specific classes of rat central nervous system macroglia has greatly advanced our understanding of how these cells are related. In particular, it has been shown in tissue culture that oligodendrocytes and some astrocytes (type-2) may be derived from a common progenitor cell (O-2A progenitor). However, the existence of type-2 astrocytes in vivo has yet to be unequivocally established. Recently, it has been reported that the neural-specific growth-associated protein-43 (GAP-43, otherwise known as B-50, F1, pp46 and neuromodulin) may be expressed by cells of the O-2A lineage in vitro. We set out to examine the cellular specificity of GAP-43 in O-2A progenitors and their descendants in vitro and in vivo. Using a polyclonal antiserum against a GAP-43 fusion protein we have shown the presence of immunoreactive GAP-43 in the membranes of bipotential O-2A glial progenitor cells and type-2 astrocytes by Western blotting and immunocytochemistry of cells in culture. In contrast to previous studies, double labelling with mature oligodendrocyte markers showed that GAP-43 is down-regulated during oligodendrocyte differentiation in vitro. Immunohistochemical staining of sections of developing rat brain demonstrated the same developmental regulation of GAP-43, suggesting that oligodendrocytes only express GAP-43 at immature stages. In addition, normal and reactive astrocytes in tissue sections were not labelled with GAP-43.

The isolation of cultured oligodendrocytes from rat optic nerve

Oligodendrocytes, the myelin-forming cells of the central nervous system, were cultured from newborn rat optic nerve employing a modified method of McCarthy and DeVellis, and cultured oligodendrocytes were analyzed for characteristic morphology and maturation events by phase contrast, MBP immunofluorescent and scanning electron microscopy. Two types of oligodendrocytes, type 1 OLs and type 2 OLs, on poly-L-lysine-coated dishes were obtained. Type 1 OLs showed extensive networks of processes and type 2 OLs elaborated membranous expansion along extensive networks, and it was demonstrated that type 2 OLs developed from type 1 OLs by phase contrast-microscopic observation. By scanning electron-microscopic observation, membrane structure in type 2 OLs clearly corresponded to membranous expansion. Our results suggest that type 1 OLs and type 2 OLs are in the different states of the myelinogenesis, and that membranous expansion and membrane structure in type 2 OLs correspond to myelin membrane.

Morphological distribution of MBP-like immunoreactivity in the brain during development

Myelin-basic protein (MBP)-like immunoreactivity was studied during development from postnatal day 1 to day 21 as a marker for the myelination process in the rat brain. Using monoclonal MBP antibodies, the caudo-rostral successive progression of MBP immunoreactivity was mapped in 1-, 7-, 14-, and 21-day-old animals using fluorescence microscopy of both coronal and sagittal sections. At 1 day of age, MBP-immunoreactive single fibers were seen in the lower brain stem, especially in formatio reticularis, whereas the rest of the brain was negative. In 1-week-old animals, MBP-positive fibers extended all the way into frontal cortex, but still in sparse arrays of single fibers with the largest number at the brain stem level. The 2-week stage showed a dramatic increase in the number of MBP-immunoreactive fibers. At the brain stem level, MBP-positive fiber plexuses were mixed with MBP-positive longitudinal axonal pathways. In cerebellar cortex, positive fibers began to radiate out from the white matter into the grey matter. A dense network of MBP-positive fibers was located in thalamus, and dense fluorescent fiber bundles were seen in capsula interna piercing through striatum. In cerebral cortex positive radiating fibers were considerably more numerous than at the previous stage. At the age of 3 weeks, MBP-immunoreactive fibers could be seen in networks and bundles in all parts of the brain. In the brain stem, a dense plexus of positive fibers filled formatio reticularis. In cortex cerebelli and cortex cerebri, a high density of radiating positive fibers was found. In striatum, a sparse distribution of single fibers was found in the neuropil surrounding the now strongly positive bundles of capsula interna. MBP-like immunoreactivity was followed during postnatal rat brain development and seemed to serve as a good indicator of progression of the myelinization process. With the excellent signal-to-noise ratio and the detailed morphological description of the distribution of MBP-like immunoreactivity, the present report can serve as a reference for studies of pathological disturbances of myelination in CNS as they relate to mechanical, chemical or hormonal perturbations.

Electroimmunoblotting of myelin basic protein peptides: a novel approach to the rapid characterisation of antigenic specificities of monoclonal and polyclonal anti-MBP antibodies

A rapid and sensitive method for the identification of antigenic determinants recognised by monoclonal and polyclonal antibodies directed against myelin basic protein (MBP) is described. By electroimmunoblotting a series of overlapping peptides covering the entire MBP molecule with monoclonal anti-MBP antibodies, the binding pattern of immunoreactive peptides can be rapidly determined and the reactive antigenic determinant identified. This procedure, which can be performed with both native and synthetic peptides, can also with appropriate modification, be applied to the analysis of naturally occurring or experimentally induced polyclonal anti-MBP autoantibodies.