First described in 1970, Coffin–Siris syndrome (reviewed by [37,38]) is an intellectual disability disorder that is caused by mutations in genes encoding individual subunits of the BAF (BRG1/BRM-associated factor) complex, including ARID1A, ARID1B, SMARCA2, SMARCA4 (BRG1), SMARCB1 (INI1), and SMARCE1 (BAF57) [39,40]. The gene discussed is SMARCA4; the disease is Coffin-Siris syndrome.