A related question is why the de novo missensemutations of PRPF19 and RBFOX1 andshare overlapping NDD features with the U2AF2 mutationscharacterized here.4 Similar speech/language,motor, and other NDD delays as patients harboring mutant U2AF2 havebeen observed for patients with de novo heterozygousmissense variants of the spliceosome subunit PRPF19 or the splicingfactor RBFOX1. The gene discussed is U2AF2; the disease is Neurodevelopmental delay.