Given the role of cytoplasmic FGFR1 in cell proliferation and nFGFR1 in neuronal differentiation and development, we analyzed the protein expression of FGFR1 in 2 and in 5-week-old iPSC organoids (Fig. 5). At 2 weeks, strong FGFR1 expression and high density of FGFR1+ cells, were detected in the VZ of controls, as well as schizophrenia iPSC organoids (Fig. 5a, Supplementary Fig. 4, a4 and a5). Both control and schizophrenia organoids displayed a less dense population of FGFR1 expressing cells in the IZ. The CZ cells of control organoids expressed FGFR1 (Fig. 5a), with many cells predominantly expressing FGFR1 associated with prominent nuclear speckles (Supplementary Fig. 4, a2). These speckles were previously shown to represent sites of RNA co-transcriptional processing and nFGFR1 interaction with the common transcriptional co-activator, CREB-binding protein (CBP)43.
