Expression and localization in the developing cerebellum of the carbohydrate epitopes revealed by Elec-39, an IgM monoclonal antibody related to HNK-1.

The immunochemical and immunocytochemical reactivity of an anti-carbohydrate monoclonal antibody (Elec-39), obtained against acetylcholinesterase from Electrophorus electricus electric organ, was followed during the postnatal development of the rat cerebellum. The specificity of this antibody resembles that of a family of anti-carbohydrate antibodies that includes HNK-1, L2, NC-1 and NSP-4, as well as IgMs that occur in some human neuropathies. As revealed by immunoblotting techniques, the reactivity of Elec-39 is maximum around postnatal days 10-12. At this age, the antibody reveals eight major proteins of mol. wt ranging between 14 and 150 kDa. Some of them (with mol. wts of 14, 18, 28 and 31 kDa) are transiently expressed. They correspond to previously identified glycoproteins binding to the plant lectin concanavalin A and binding also to the endogenous mannose-binding lectin CSL and endogenous membrane-bound mannose-binding lectin. In young animals, an important staining with the Elec-39 antibody can be observed on postmitotic precursors of granule cells, on astrocyte processes in the external granular layer, on newly formed parallel fibres and on unmyelinated axons of the white matter. In adult animals, the labelling is localized essentially in myelin and also in the cytoplasm of astrocytes. These results are discussed in relation to ontogenetic phenomena occurring during cerebellar development and the potential role of the carbohydrate epitope revealed with Elec-39 as a determinant in cell adhesion processes.