Among these, some well-studied disease-relevant genes are found: HTT (Huntington disease) [11], FOXP2 (language impairment) [12], CHD8 and CPEB4 (autism spectrum disorder) [13, 14], TCF4 (Pitt-Hopkins syndrome and schizophrenia) [15, 16], GLI3 (macrocephaly and Greig cephalopolysyndactyly syndrome) [17], PHC1 (primary, autosomal recessive, microcephaly-11) [18], RCAN1 (Down syndrome) [19], and DYNC1H1 (cortical malformations and microcephaly) [20]. The gene discussed is TCF4; the disease is Down syndrome.