At day 32 post-differentiation, both HD and control cultures consisted of neurons positive for striatal markers, dopamine- and cAMP-regulated neuronal phosphoprotein (DARPP-32) and COUP-TF1-interacting protein 2 (CTIP2) (Fig. 2b, quantified in Extended Data Fig. 1a,b). The gene discussed is PPP1R1B; the disease is Huntington disease.