Reelin receptors in developing laminated brain structures of mouse and human

Reelin is an extracellular matrix protein secreted by a variety of cell types throughout the developing brain. The target cells for reelin express the cytoplasmic adapter protein Dab1, which binds to the reelin receptors VLDLR and ApoER2. In the present work, we have studied the localization of both receptors in developing mouse and human cortex, olfactory bulb and cerebellum. In mouse, some Cajal-Retzius cells express reelin and VLDLR; in humans, all the components of the signalling pathway (Reelin, Dab1, VLDLR and ApoER2) are present in subsets of Cajal-Retzius cells. In the mouse cortical plate, VLDLR and ApoER2 are present from E15 to postnatal stages; in human cortical plate they are most prominent at approximately 20 gestational weeks. In mice, cerebellar Purkinje cells only express VLDLR whereas in humans they express both VLDLR and ApoER2. Mitral cells of the mouse olfactory bulb are ApoER2-positive and VLDLR-negative. In sum, the receptor expression patterns are similar in the human and mouse cortical plate but differ in Cajal-Retzius and Purkinje cells, which in humans express additional components of the reelin-Dab1 pathway.