We next investigated determinants of GABAergic inhibitory neuronal fates using DLX1-2 (two TFs which are among the earliest determinants of GABAergic fate in telencephalic precursors cells and upregulated members of the magenta module) and GAD1/GAD67 (the GABA synthetic enzyme, an upregulated member of the tan module). The expression of these GABAergic markers was increased significantly in organoids derived from ASD individuals compared to those from unaffected family members. This increase was strong at TD31 and was already detectable at TD11 (Figure 4G–J). The increase in DLX1/2 and GAD1/GAD67 was consistent in probands irrespectively of iPSC line, or individuals within different families (Figure S4G–L). Also, the increases in DLX1/2 and GAD1 in probands with respect to their fathers were reproducible across independent differentiation experiments (Figure S4M).
