PD173074 was shown previously to reduce nuclear nFGFR1 accumulation observed in pancreatic tumors57. Hence, we examined the PD173074 effect on FGFR1 subcellular distribution in the CZ of hESC H9 cerebral organoids. In several independent experiments, the expression of FGFR1 in control hESC H9 organoids showed similar patterns (Fig. 8a) as in the control iPSC organoids (Fig. 5a). FGFR1 was highly expressed in the VZ cells (Fig. 8a). The FGFR1 staining was less intense in the IZ and stronger again in the CZ. In many CZ cells, FGFR1 localized within the cell nuclei (Fig. 8a) and in prominent nuclear speckles (Fig. 8, b1). To quantify the changes in FGFR1 subcellular distribution, we imaged DAPI and FGFR1 co-stained sections using confocal microscopy (Fig. 8b). In the CZ of control organoids, 52% of cells had nFGFR1 colocalized with DAPI. In PD173074-treated organoids there was over a three-fold reduction in the number of cells with nFGFR1 in the CZ (Fig. 8c), likely reflecting loss of the positive fgfr1 gene activation by its protein19,57.
