To date, seven biallelic human disease variants have been reportedto be located in ADARB1 (gene encoding ADAR2).63,64 These patients show severe developmental delay, microcephaly, andintellectual disability, and some have intractable early infantile-onsetseizures (Table 1).ADAR2 is responsible for editing the Q/R position in the GRIA2 transcript and mice lacking Adarb1 have seizuresand die with 3 weeks of birth.45 However,this mouse mutant phenotype is rescued by knocking in the edited versionof Gria2R. The gene discussed is ADARB1; the disease is Global developmental delay.