CTNNB1 monoallelic pathogenic variants account for up to 4% of genetically determined cerebral palsy cases, yet their phenotypic spectrum remains poorly defined. We retrospectively analyzed 25 individuals with pathogenic CTNNB1 variants using medical records and a questionnaire. Data included genetic variants, perinatal history, developmental milestones, behavioral characteristics, head growth, feeding, sleep difficulties, neurological and ophthalmological assessments. Brain MRIs were reviewed by expert neuroradiologists. Twenty-two distinct heterozygous variants were identified. Microcephaly occurred in 16/22 patients. All exhibited global developmental delay, independent walking was achieved at a mean age of 2.1 years, with regression in 4/16 independent walkers. Behavioral disorders were frequent, as were oral sensorimotor disorders (21/25) and sleep disturbances (13/21). Lower limb hypertonia was present in 22/25 patients [spastic (8) and/or dystonic (11)]. Unstable gait were common among ambulatory patients. Exaggerated startle reactions, often since birth, were reported in 16/21. Exudative vitreoretinopathy was identified in 3/5 patients with retinal angiography. Brain MRI (19 patients) showed: thickening of anterior commissure (8), frontal lobe hypoplasia (9), widening of superior vermian sulci (10) and corpus callosum anomalies (7). This study broadens the spectrum of CTNNB1-related syndrome, reporting a complex motor phenotype combining (i) gait disturbances related to dystonic or non-dystonic hypertonia and unsteadiness, sometimes associated to dystonia in other body parts (ii) possible deterioration of motor achievements over the course of the disease (iii) an exaggerated startle reflex. New non-specific brain anomalies are precisely described. Our work underscores the need for registries and longitudinal studies to refine characterization and guide future therapies.

GNAO1-related disorders (GNAO1-RD) encompass a wide phenotypic spectrum, including muscular hypotonia, movement disorders (MD), epilepsy, developmental delay, and intellectual disability. MD often presents with dystonia and choreoathetosis, and dyskinetic crises can lead to life-threatening conditions. Despite increasing reports, limited information exists on the impact of upper airway dysfunction in GNAO1-RD patients. This study examines the implications of muscular hypotonia on upper airway function and subsequent clinical outcomes. This study includes four patients, three from the GNAO1 registry in Germany, with data collected from medical records including neurological examinations, EEG recordings, genetics, imaging studies, and video documentation of dyskinetic movements and respiratory symptoms. Treatment interventions and clinical outcomes were documented. The study involved four patients (three males and one female) aged between 15 months and 12 years, all of whom were within the severe spectrum of GNAO1-RD. All patients exhibited severe hypotonia and hyperkinetic MD, leading to recurrent dyskinetic crises. Respiratory complications included an inspiratory stridor and airway obstructions. All patients died at young age (2.4, 2.8, 7.8 and 12 years) due to respiratory complications. Despite interventions such as DBS and tracheostomy, clinical outcomes remained poor. Upper airway dysfunction significantly contributes to the high morbidity and mortality in GNAO1-RD patients. Current therapeutic options are limited; while DBS can be life-saving during acute crises, it does not address swallowing or airway dysfunction effectively. Multimodal approaches and larger, multicenter trials are needed to improve outcomes for these patients. GNAO1-related disorder encompasses a broad phenotypic continuum that includes hyperkinetic movement disorders and/or epilepsy and is typically associated with developmental delay and intellectual disability. Viewed by age of onset, three clusters in this continuum can be observed: (1) infantile-onset developmental and epileptic encephalopathy (DEE) with or without prominent movement disorder; (2) infantile- or early childhood-onset prominent movement disorder and neurodevelopmental disorder with or without childhood-onset epilepsy with varying seizure types; (3) later childhood- or adult-onset movement disorder with variable developmental delay and intellectual disability. Epilepsy can be either DEE (onset typically within the first year of life of drug-resistant epilepsy in which developmental delays are attributed to the underlying diagnosis as well as the impact of uncontrolled seizures) or varying seizure types (onset typically between ages three and ten years of focal or generalized tonic-clonic seizures that may be infrequent or well controlled with anti-seizure medications). Movement disorders are characterized by dystonia and choreoathetosis, most commonly a mixed pattern of persistent or paroxysmal dyskinesia that affects the whole body. Exacerbations of the hyperkinetic movement disorder, which can be spontaneous or triggered (e.g., by intercurrent illness, emotional stress, voluntary movements), can last minutes to weeks. Hyperkinetic crises (including status dystonicus) are characterized by temporarily increased and nearly continuous involuntary movements or dystonic posturing that can be life-threatening. Deaths in early childhood have been reported due to medically refractory epilepsy or hyperkinetic crises, but the phenotypic spectrum includes milder presentations, including in adults. As many adults with disabilities have not undergone advanced genetic testing, it is likely that adults with GNAO1-related disorder are underrecognized and underreported. The diagnosis of GNAO1-related disorder is established in a proband with suggestive findings and a heterozygous pathogenic variant in GNAO1 identified by molecular genetic testing. Treatment of manifestations: There is no cure for GNAO1-related disorder. Supportive care to improve quality of life, maximize function, and reduce complications can include multidisciplinary care by specialists in child neurology, adult neurology, neurosurgery, physical medicine and rehabilitation, physical therapy, occupational therapy, orthopedic surgery, speech-language therapy, and psychology. Surveillance: Frequent evaluations by treating specialists are necessary to monitor existing manifestations, the individual's response to supportive care, and the emergence of new manifestations. GNAO1-related disorder is an autosomal dominant disorder most often caused by a de novo pathogenic variant. Individuals with severe GNAO1-related disorder phenotypes (i.e., DEE, severe developmental delay and/or intellectual disability, and/or an early-onset movement disorder) typically represent simplex cases (i.e., the only family member known to be affected) and have the disorder as the result of a de novo pathogenic variant; however, recurrence of severe GNAO1-related disorder phenotypes in affected sibs due to presumed parental germline mosaicism has been reported. Vertical transmission from an affected parent to an affected child has been reported in several families with the milder phenotype (i.e., later childhood- or adult-onset movement disorder with variable developmental delay and intellectual disability). Once the GNAO1 pathogenic variant has been identified in an affected family member, prenatal and preimplantation genetic testing are possible.

The etiology of severe childhood speech disorders, including childhood apraxia of speech (CAS), is currently understood as genetically heterogeneous, with over 40 distinct monogenic conditions reported to date. Among them, the p.Thr327Arg variant in GNAO1, encoding the major neuronal G protein Gαo, was identified in one patient diagnosed with CAS and intellectual disability (ID). This presentation is exceptionally rare, as GNAO1 mutations are commonly associated with epilepsy, hyperkinetic movement disorders, and global developmental delay, often accompanied by ID. Here, we describe the clinical course of two patients with de novo heterozygous GNAO1 variants-p.Leu39_Gly40insVal and p.Thr327Lys-who exhibit severe speech disorder and ID as prominent symptoms. We also analyzed the biochemical and cellular properties of the mutant Gαo proteins alongside the previously reported p.Thr327Arg variant. Molecular investigation of these three atypical Gαo mutants revealed aberrant GTP binding and hydrolysis, impaired association with RGS19, and a strong neomorphic gain of Ric8A interaction. Yet, all variants show normal plasma membrane localization despite poor Gβγ association, with p.Leu39_Gly40insVal exhibiting weak coupling to G protein-coupled receptors and p.Thr327Arg/Lys displaying near-normal coupling. Importantly, all three Gαo variants respond to Zn2+, supporting the potential therapeutic use of zinc supplementation for the patients. These rare findings are based on a limited number of cases and require confirmation in additional patients to establish firmer genotype-phenotype correlations for GNAO1-related severe speech disorders. Our results broaden the clinical and mechanistic spectrum of GNAO1-related disorders, showing that severe speech disorders and ID can occur as defining features even in the absence of seizures or movement disorders. These findings highlight the importance of including GNAO1 in genetic testing for children with severe speech disorders.

To evaluate clinical phenotype and molecular findings of 157 cases with GNAO1 pathogenic or likely pathogenic variants delineating the clinical spectrum, course, and response to treatments. Clinical phenotype, genetic data, and pharmacological and surgical treatment history of 11 novel cases and 146 previously published patients were analyzed. Complex hyperkinetic movement disorder (MD) characterizes 88% of GNAO1 patients. Severe hypotonia and prominent disturbance of postural control seem to be hallmarks in the early stages preceding the hyperkinetic MD. In a subgroup of patients, paroxysmal exacerbations became so severe as to require admission to intensive care units (ICU). Almost all patients had a good response to deep brain stimulation (DBS). Milder phenotypes with late-onset focal/segmental dystonia, mild to moderate intellectual disability, and other minor neurological signs (i.e., parkinsonism and myoclonus) are emerging. MRI, previously considered noncontributory to a diagnosis, can show recurrent findings (i.e., cerebral atrophy, myelination and/or basal ganglia abnormalities). Fifty-eight GNAO1 pathogenic variants, including missense changes and a few recurrent splice site defects, have been reported. Substitutions at residues Gly203, Arg209 and Glu246, together with the intronic c.724-8G > A change, account for more than 50% of cases. Infantile or childhood-onset complex hyperkinetic MD (chorea and/or dystonia) with or without paroxysmal exacerbations, associated hypotonia, and developmental disorders should prompt research for GNAO1 mutations. DBS effectively controls and prevents severe exacerbations and should be considered early in patients with specific GNAO1 variants and refractory MD. Prospective and natural history studies are necessary to define genotype-phenotype correlations further and clarify neurological outcomes.

GNAO1-related encephalopathies include a broad spectrum of developmental disorders caused by de novo heterozygous mutations in the GNAO1 gene, encoding the G (o) subunit α of G-proteins. These conditions are characterized by epilepsy, movement disorders and developmental impairment, in combination or as isolated features. This study aimed at describing the profile of neurovisual competences in children with GNAO1 deficiency to better characterize the phenotype of the disease spectrum. Four male and three female patients with confirmed genetic diagnosis underwent neurological examination, visual function assessment, and neurovisual and ophthalmological evaluation. Present clinical history of epilepsy and movement disorders, and neuroimaging findings were also evaluated. The assessment revealed two trends in visual development. Some aspects of visual function, such as discrimination and perception of distance, depth and volume, appeared to be impaired at all ages, with no sign of improvement. Other aspects, reliant on temporal lobe competences (ventral stream) and more related to object-face exploration, recognition and environmental control, appeared to be preserved and improved with age. Visual function is often impaired, with patterns of visual impairment affecting the ventral stream less.