Phenotypic Diversity in GNAO1 Patients: A Comprehensive Overview of Variants and Phenotypes

GNAO1 disorder is a rare autosomal dominant neurodevelopmental syndrome that is clinically manifested by developmental delay, (early onset) epilepsy, and movement disorders. Clinical symptoms appear very heterogeneous in nature and severity, as well as the response of GNAO1 patients to available medication varies. Pathogenic GNAO1 variants have been found mainly scattered throughout the gene although certain mutation hotspots affecting the function of the encoded G & alpha;o proteins exist. GNAO1 variants only partially explain the diverse phenotypic spectrum observed but full stratification has been hampered by the limited number of patients. The aim of this review was to generate a comprehensive overview of the germline variants in GNAO1 and provide insight into the phenotypic diversity of the GNAO1 disorder. We compiled a list of 398 GNAO1 germline variants. In addition, we provide the GNAO1 variants and associated phenotypes of 282 GNAO1 patients reported in case reports, whole genome sequencing studies, genetic variant databases, and 8 novel GNAO1 patients that were not described before. This has resulted in a list of 107 (likely) pathogenic GNAO1 variants. Available phenotypic data was utilized to quantitatively assess the genetic and phenotypic diversity of the GNAO1 disorder and discuss the outcomes. This inventory forms the basis for a GNAO1 variant database that will be updated continuously. Moreover, it will aid genetic diagnostics, medical decision-making, prognostication, and research on the mechanisms underlying the GNAO1 disorder.