GNAO1A variants are much more frequently observed in these 90 NDD patients than variants in GNAO1B. Six out of 90 isoform-specific variants are in GNAO1B. This underrepresentation of GNAO1B variants indicates that mutations in GNAO1A are likely the predominant cause of the GNAO1 disorder. The gene discussed is GNAO1; the disease is Neurodevelopmental delay.