Coordinate expression of L1 and 6B4 proteoglycan/phosphacan is correlated with the migration of mesencephalic dopaminergic neurons in mice

Abstract

Mesencephalic dopaminergic (DA) neurons of mice are generated from embryonic day 10 to 12 (E10–12) in the ventricular zone of the mesencephalon. They first migrate toward the ventral mesencephalon, and then turn laterally, or tangentially, in the basal part of the mesencephalon. With immunohistochemical analysis of E10–E15 ICR mice, we found that cell adhesion molecule L1 was transiently expressed on the median part of tangential fibers coincident with the lateral migration of DA neurons from E11 to E13, when neurons move along the tangential fibers toward their final destinations: the reticular formation, the substantia nigra pars compact, and the ventral tegmental area. While L1 expression was not observed in DA neurons, they expressed a chondroitin sulfate proteoglycan, 6B4 proteoglycan/phosphacan, which has been shown to bind to L1/Ng-CAM in vitro. These results suggest that the heterophilic interaction between 6B4 proteoglycan on the neurons and L1 on the fibers is involved in the lateral migration of mesencephalic DA neurons in mice.