RBFOX1 and Neurodevelopmental delay: 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.