Two patterns in apical dendrite extensions of projection neurons within cerebral cortex of reeler mutant mice

Reeler CS neurons displayed a congregation pattern of apical dendritic terminal tips in a specific upper cortical zone, whereas reeler CC neurons exhibited a dispersed pattern of scattered tips throughout the cortex. However, reeler CT neurons showed a hybrid pattern, exhibiting characteristics of both congregation- and dispersion-type neurons. Moreover, apical dendrite extension of these projection neurons follows either a congregation or dispersion mode from postnatal day 0 (P0), which subsequently defines their terminal tip positioning by P8. Thus, this early patterning of apical dendrite arborization in reeler projection neurons likely contributes to the formation of projection target-specific neuronal connections during the first two postnatal weeks.