Using human brain organoids derived from iPSCs of DS patients, it was found that DS ventral forebrain organoid overproduced OLIG2+ progenitors, and consequently showed an overproduction of inhibitory interneurons (GABAergic neurons), in accordance with the impaired excitatory and inhibitory balance in DS patients (Xu et al. 2019). The gene discussed is OLIG2; the disease is Dravet syndrome.