Figure 1.

Migration of midbrain dopaminergic (mDA) neurons. (A) Sagittal view of embryonic brain. Red line indicates level of coronal sections in (B,D,E). (B) Expression patterns of Reelin (red), Dab1 (yellow), ApoER2 (green) and very low density lipoprotein receptor (VLDLR; green) at the indicated time point. Red triangles in the mDA neuron region indicate Reelin secreted by striatal projections. Reelin and Dab1 expression are only presented in the left half of the brain, ApoER2 and VLDLR expression are only presented in the right half of the brain. Expression in the dorsal midbrain is not included in the schematic. (C) Expression of Reelin, Dab1, ApoER2 and VLDLR in the midbrain is maintained into adulthood. (D) Schematic of migratory paths of mDA neurons in wildtype (left half of the brain) and reeler mice (right half of the brain). Black arrows indicate radial migration, red arrows indicate tangential migration. Tangential migration is truncated in reeler mutants (D^′,D^″). In wildtype mice (D^′), processes of migrating mDA neurons are oriented tangentially, in reeler mice (D^″) processes are oriented radially. (E) mDA neuron distribution in E18.5 wildtype mice (left half of the brain) and reeler mutants (right half of the brain). Turquoise dots represent Calbindin positive mDA neurons of the ventral tegmental area (VTA); dark green dots represent Girk2 positive mDA neurons of the substantia nigra (SN). SN-mDA neurons separate from VTA-mDA neurons but fail to reach their normal lateral location in reeler mice (arrow).