TBR1 and fragile X syndrome: Increased expression of genes required for specification of a dorsal telencephalic precursor fate were identified in both control and FXS- hiDFPs, including FOXG1, NGN2, TBR2, TBR1 and CTIP2. This is also consistent with decreased expression of the ventral forebrain marker DLX2. The pan-precursor marker Nestin was also highly expressed across all hiDFPs cohorts.