To determine if FGFR1 inhibition affected the ongoing cortical neuronogenesis, we pulse labeled dividing cells with BrdU in 14-day organoids (6th day of PD173074 treatment). After an additional 4 days, BrdU-labeled control or PD173074-treated organoids were sectioned and co-immunostained with rat anti-BrdU and with mouse anti-Pan-Neu. In control organoids, the BrdU-labeled cells were found in the VZ, as well as migrated into the IZ and CZ (Fig. 7c). Counting cells in multiple rosettes showed BrdU+ cells abundantly present in all zones of the control organoids in the following order: VZ > IZ > CZ. In contrast, in PD173074-treated organoids, BrdU+ cells were most abundant in the IZ with only few cells present in the cortex (IZ > VZ > CZ) (Fig. 7c and Table 4).Table 4Effect of PD173074 on distribution of BrdU+ cells and double labeled BrdU+ plus Pan-Neu+ cells in rosettes and in the cortical zoneControlPD173074Rosette ROIsBrdUBrdU47.7 ± 3.4 (77%)136.2 ± 22.7 (98%) P = 0.006BrdU + Pan-NeuBrdU + Pan-Neu18.3 ± 1.7 (74%)9.2 ± 2.6 (93%) P = 0.008Cortex ROIsBrdUBrdU14.2 ± 2.1 (23%)2.5 ± 0.9 (2%) P = 0.0007BrdU
