In control organoids, BrdU and Pan-Neu colocalized predominantly in the same cells of the marginal CZ (Fig. 7c, Supplementary Fig. 9a), indicating that the dividing VZ cells had migrated out to cortical layers and differentiated into neurons. Treatment with PD173074 markedly altered this process (Fig. 7c, Supplementary Fig. 9b). The BrdU+ cells remained largely arrested in the IZ. Relatively few BrdU+ cells that were found in the CZ differentiated to Pan-Neu positive neurons (Table 4). Thus, blocking FGFR1-inhibited cortical migration of the newborn cells and formation of mature neurons.
