5'-Nucleotidase in postnatal ontogeny of rat cerebellum: a marker for migrating nerve cells?

The distribution of the ectoenzyme 5'-nucleotidase was studied in the developing rat cerebellum using enzyme- and immunocytochemical techniques in order to evaluate its appearance in the processes of cellular migration during nervous system development. 5'-Nucleotidase enzymatic activity appeared first in the external granular layer (postnatal day 6). Then, the inner portion of the external granular layer and the developing molecular layer became prominently stained (postnatal day 12). At 21 days the adult pattern was established with a diffuse labeling of the whole molecular layer. Additionally, 5'-nucleotidase enzymatic activity was found around Purkinje cells. At the ultrastructural level migrating nerve cells exhibited an intense surface labeling whereas resting neuroblasts of the external granular layer as well as all post-migratory nerve cells were negative. Immunocytochemistry differed from enzyme histochemistry in that immunoreactivity was found to be selectively associated with glial elements. It is suggested that 5'-nucleotidase may serve as a marker for processes of neuronal migration and neuron-glia interactions during postnatal ontogeny. Underlying mechanisms could be due to an interaction of 5'-nucleotidase with the extracellular matrix molecule, laminin, and cytoskeletal actin involved in locomotion.