Phenotypic spectrum of GNAO1 variants: epileptic encephalopathy to involuntary movements with severe developmental delay

A patient with a GNAO1 mutation with decreased spontaneous movements, hypotonia, and dystonic features

We report on a 4-year-old girl with a de novo GNAO1 mutation who had neurological findings, including decreased spontaneous movements, hypotonia, and dystonic features. She was referred to our hospital because of delayed psychomotor development. She showed hypotonia and decreased spontaneous movements. Voluntary movements of the limbs were more frequent in the lower extremities than in the upper extremities. Occasional dyskinetic features, such as awkward hand/foot posturing and grimacing, were seen during the voluntary movements. Serum metabolic screening, head magnetic resonance imaging, and electroencephalography were unremarkable. Whole-exome sequencing revealed a de novo mutation in the patient's GNAO1 gene, c.709 G > A (p.E237K). We calculated the free-energy change using the FoldX Suite to evaluate the impact of the E237K mutation. The FoldX calculations showed an increased free-energy change in the active state of the GNAO1 protein, indicating that the E237K mutation destabilizes the active state complexes. No seizures, chorea, tremor, or myoclonia, which are frequently reported in patients with GNAO1 mutations, were observed as of the last follow up. Our patient will improve the understanding of early neurological features in patients with GNAO1 mutations.

Postsynaptic movement disorders: clinical phenotypes, genotypes, and disease mechanisms

Movement disorders comprise a group of heterogeneous diseases with often complex clinical phenotypes. Overlapping symptoms and a lack of diagnostic biomarkers may hamper making a definitive diagnosis. Next-generation sequencing techniques have substantially contributed to unraveling genetic etiologies underlying movement disorders and thereby improved diagnoses. Defects in dopaminergic signaling in postsynaptic striatal medium spiny neurons are emerging as a pathogenic mechanism in a number of newly identified hyperkinetic movement disorders. Several of the causative genes encode components of the cAMP pathway, a critical postsynaptic signaling pathway in medium spiny neurons. Here, we review the clinical presentation, genetic findings, and disease mechanisms that characterize these genetic postsynaptic movement disorders.

Identify Cross Talk Between Circadian Rhythm and Coronary Heart Disease by Multiple Correlation Analysis

Disorder in circadian rhythm has been revealed as a risk factor for coronary heart disease. Several studies in molecular biology established a gene interaction network using coronary heart susceptibility genes and the circadian rhythm pathway. However, cross talk between genes was mostly discovered in single gene pairs. There might be combination sets of genes intergraded as a unit to regulate the network. To resolve multiple variables in coronary heart susceptibility genes controlling circadian rhythm pathways, a multiple correlation analysis was applied to the transcriptome. Nine genes, including CUGBP, Elav-like family member (CELF); sodium leak channel, nonselective (NALCN); protein phosphatase 2 regulatory subunit B gamma (PPP2R2C); tubulin alpha 1c (TUBA1C); microtubule-associated protein 4 (MAP4); cofilin 1 (CFL1); myosin heavy chain 7 (MYH7); QKI, KH domain containing RNA binding (QKI); and maternal embryonic leucine zipper kinase (MELK), from coronary heart susceptibility were identified to predict the outcome of a linear combination of circadian rhythm pathway genes with R factor more than 0.7. G protein subunit alpha o1 (GNAO1), protein kinase C gamma (PRKCG), RBX, and G protein subunit beta 1 (GNB1) in the circadian rhythm pathway are characterized as combination variables to coexpress with coronary heart susceptibility genes.

Neonatal epileptic encephalopathy caused by de novo GNAO1 mutation misdiagnosed as atypical Rett syndrome: Cautions in interpretation of genomic test results

Epileptic encephalopathies are childhood brain disorders characterized by a variety of severe epilepsy syndromes that differ by the age of onset and seizure type. Until recently, the cause of many epileptic encephalopathies was unknown. Whole exome or whole genome sequencing has led to the identification of several causal genes in individuals with epileptic encephalopathy, and the list of genes has now expanded greatly. Genetic testing with epilepsy gene panels is now done quite early in the evaluation of children with epilepsy, following brain imaging, electroencephalogram, and metabolic profile. Early infantile epileptic encephalopathy (EIEE1; OMIM #308350) is the earliest of these age-dependent encephalopathies, manifesting as tonic spasms, myoclonic seizures, or partial seizures, with severely abnormal electroencephalogram, often showing a suppression-burst pattern. In this case study, we describe a 33-month-old female child with severe, neonatal onset epileptic encephalopathy. An infantile epilepsy gene panel test revealed 2 novel heterozygous variants in the MECP2 gene; a 70-bp deletion resulting in a frameshift and truncation (p.Lys377ProfsX9) thought to be pathogenic, and a 6-bp in-frame deletion (p.His371_372del), designated as a variant of unknown significance. Based on this test result, the diagnosis of atypical Rett syndrome (RTT) was made. Family-based targeted testing and segregation analysis, however, raised questions about the pathogenicity of these specific MECP2 variants. Whole exome sequencing was performed in this family trio, leading to the discovery of a rare, de novo, missense mutation in GNAO1 (p. Leu284Ser). De novo, heterozygous mutations in GNAO1 have been reported to cause early infantile epileptic encephalopathy-17 (EIEE17; OMIM 615473). The child's severe phenotype, the family history and segregation analysis of variants and prior reports of GNAO1-linked disease allowed us to conclude that the GNAO1 mutation, and not the MECP2 variants, was the cause of this child's neurological disease. With the increased use of genetic panels and whole exome sequencing, we will be confronted with lists of gene variants suspected to be pathogenic or of unknown significance. It is important to integrate clinical information, genetic testing that includes family members and correlates this with the published clinical and scientific literature, to help one arrive at the correct genetic diagnosis.

A mechanistic review on GNAO1-associated movement disorder

Mutations in the GNAO1 gene cause a complex constellation of neurological disorders including epilepsy, developmental delay, and movement disorders. GNAO1 encodes Gα_o, the α subunit of G_o, a member of the G_i/o family of heterotrimeric G protein signal transducers. G_o is the most abundant membrane protein in the mammalian central nervous system and plays major roles in synaptic neurotransmission and neurodevelopment. GNAO1 mutations were first reported in early infantile epileptic encephalopathy 17 (EIEE17) but are also associated with a more common syndrome termed neurodevelopmental disorder with involuntary movements (NEDIM). Here we review a mechanistic model in which loss-of-function (LOF) GNAO1 alleles cause epilepsy and gain-of-function (GOF) alleles are primarily associated with movement disorders. We also develop a signaling framework related to cyclic AMP (cAMP), synaptic vesicle release, and neural development and discuss gene mutations perturbing those mechanisms in a range of genetic movement disorders. Finally, we analyze clinical reports of patients carrying GNAO1 mutations with respect to their symptom onset and discuss pharmacological/surgical treatments in the context of our mechanistic model.

Inherited and Acquired Choreas

Chorea is a symptom of a broad array of genetic, structural, and metabolic disorders. While chorea can result from systemic illness and damage to diverse brain structures, injury to the basal ganglia, especially the putamen or globus pallidus, appears to be a uniting features of these diverse neuropathologies. The timing of onset, rate of progression, and the associated neurological or systemic symptoms can often narrow the differential diagnosis to a few disorders. Recognizing the correct etiology for childhood chorea is critical, as numerous disorders in this category are potentially curable, or are remediable, with early treatment.

Genomic analysis identifies masqueraders of full-term cerebral palsy

Objective

Cerebral palsy is a common, heterogeneous neurodevelopmental disorder that causes movement and postural disabilities. Recent studies have suggested genetic diseases can be misdiagnosed as cerebral palsy. We hypothesized that two simple criteria, that is, full-term births and nonspecific brain MRI findings, are keys to extracting masqueraders among cerebral palsy cases due to the following: (1) preterm infants are susceptible to multiple environmental factors and therefore demonstrate an increased risk of cerebral palsy and (2) brain MRI assessment is essential for excluding environmental causes and other particular disorders.

Methods

A total of 107 patients-all full-term births-without specific findings on brain MRI were identified among 897 patients diagnosed with cerebral palsy who were followed at our center. DNA samples were available for 17 of the 107 cases for trio whole-exome sequencing and array comparative genomic hybridization. We prioritized variants in genes known to be relevant in neurodevelopmental diseases and evaluated their pathogenicity according to the American College of Medical Genetics guidelines.

Results

Pathogenic/likely pathogenic candidate variants were identified in 9 of 17 cases (52.9%) within eight genes: CTNNB1,CYP2U1,SPAST,GNAO1,CACNA1A,AMPD2,STXBP1, and SCN2A. Five identified variants had previously been reported. No pathogenic copy number variations were identified. The AMPD2 missense variant and the splice-site variants in CTNNB1 and AMPD2 were validated by in vitro functional experiments.

Interpretation

The high rate of detecting causative genetic variants (52.9%) suggests that patients diagnosed with cerebral palsy in full-term births without specific MRI findings may include genetic diseases masquerading as cerebral palsy.

Placental CpG methylation of infants born extremely preterm predicts cognitive impairment later in life

Background

The placenta is the central regulator of maternal and fetal interactions. Perturbations of placental structure and function have been associated with adverse neurodevelopmental outcomes later in life. Placental CpG methylation represents an epigenetic modification with the potential to impact placental function, fetal development and child health later in life.

Study design

Genome-wide placental CpG methylation levels were compared between spontaneous versus indicated deliveries from extremely preterm births (EPTBs) (n = 84). The association between the identified differentially methylated CpG sites and neurocognitive outcome at ten years of age was then evaluated.

Results

Spontaneous EPTB was associated with differential CpG methylation levels in 250 CpG sites (217 unique genes) with the majority displaying hypermethylation. The identified genes are known to play a role in neurodevelopment and are enriched for basic helix-loop-helix transcription factor binding sites. The placental CpG methylation levels for 17 of these sites predicted cognitive function at ten years of age.

Conclusion

A hypermethylation signature is present in DNA from placentas in infants with spontaneous EPTB. CpG methylation levels of critical neurodevelopment genes in the placenta predicted later life cognitive function, supporting the developmental origins of health and disease hypothesis (DOHaD).

[Recurrent convulsion and pulmonary infection complicated by psychomotor retardation in an infant]

A 4-month-old girl developed convulsion in the neonatal period, which was focal motor seizures in the initial stage and later became spasm and tonic spasm. And the girl also had psychomotor retardation and recurrent pulmonary infection. Electroencephalography showed hypsarrhythmia, normal results were obtained from cranial magnetic resonance imaging, cerebrospinal fluid examination, and urine organic acid analysis, as well as the spectral analyses of blood ammonia, blood lactic acid, blood amino acids, and acylcarnitines. Gene detection revealed a de novo heterozygous mutation, c.607G>A (p.G203R) , in GNAO1. The girl was then diagnosed with GNAO1-associated early infantile epileptic encephalopathy (EIEE type 17). The seizures were well controlled by topiramate and vigabatrin, but there was no improvement in psychomotor development. She also suffered from recurrent pulmonary infection and died at the age of 12 months due to severe pneumonia. For children with unexplained early infantile epileptic encephalopathy, GNAO1 gene mutations should be considered and genetic tests should be performed as early as possible. Recurrent pulmonary infection should also be taken seriously.

Emerging Monogenic Complex Hyperkinetic Disorders

Purpose of Review

Hyperkinetic movement disorders can manifest alone or as part of complex phenotypes. In the era of next-generation sequencing (NGS), the list of monogenic complex movement disorders is rapidly growing. This review will explore the main features of these newly identified conditions.

Recent Findings

Mutations in ADCY5 and PDE10A have been identified as important causes of childhood-onset dyskinesias and KMT2B mutations as one of the most frequent causes of complex dystonia in children. The delineation of the phenotypic spectrum associated with mutations in ATP1A3, FOXG1, GNAO1, GRIN1, FRRS1L, and TBC1D24 is revealing an expanding genetic overlap between epileptic encephalopathies, developmental delay/intellectual disability, and hyperkinetic movement disorders,.

Summary

Thanks to NGS, the etiology of several complex hyperkinetic movement disorders has been elucidated. Importantly, NGS is changing the way clinicians diagnose these complex conditions. Shared molecular pathways, involved in early stages of brain development and normal synaptic transmission, underlie basal ganglia dysfunction, epilepsy, and other neurodevelopmental disorders.

Prospective cohort study for identification of underlying genetic causes in neonatal encephalopathy using whole-exome sequencing

PurposeNeonatal encephalopathy, which is characterized by a decreased level of consciousness, occurs in 1-7/1,000 live-term births. In more than half of term newborns, there is no identifiable etiological factor. To identify underlying genetic defects, we applied whole-exome sequencing (WES) in term newborns with neonatal encephalopathy as a prospective cohort study.MethodsTerm newborns with neonatal encephalopathy and no history of perinatal asphyxia were included. WES was performed using patient and both parents' DNA.ResultsNineteen patients fulfilling inclusion criteria were enrolled. Five patients were excluded owing to withdrawal of consent, no parental DNA samples, or a genetic diagnosis prior to WES. Fourteen patients underwent WES. We confirmed a genetic diagnosis in five patients (36%): epileptic encephalopathy associated with autosomal dominant de novo variants in SCN2A (p.Met1545Val), KCNQ2 (p.Asp212Tyr), and GNAO1 (p.Gly40Arg); lipoic acid synthetase deficiency due to compound heterozygous variants in LIAS (p.Ala253Pro and p.His236Gln); and encephalopathy associated with an X-linked variant in CUL4B (p.Asn211Ser).ConclusionWES is helpful at arriving genetic diagnoses in neonatal encephalopathy and/or seizures and brain damage. It will increase our understanding and probably enable us to develop targeted neuroprotective treatment strategies.

Impact of clinical exomes in neurodevelopmental and neurometabolic disorders

Whole exome sequencing (WES) is well established in research and is now being introduced into clinically indicated diagnostics (so-called clinical exomes). We evaluated the diagnostic yield and clinical implications of WES in 72 patients from 60 families with undiagnosed neurodevelopmental disorders (NDD), neurometabolic disorders, and dystonias. Pathogenic or likely pathogenic variants leading to a molecular diagnosis could be identified in 21 of the 60 families (overall 35%, in 36% of patients with NDD, in 43% of patients with neurometabolic disorders, in 25% of patients with dystonias). In one family two coexisting autosomal recessive diseases caused by homozygous pathogenic variants in two different genes were diagnosed. In another family, a homozygous frameshift variant in STRADA was found to cause a severe NDD with early onset epilepsy, brain anomalies, hypotonia, heart defect, nephrocalcinosis, macrocephaly and distinctive facies so far designated as PMSE (polyhydramnios, megalencephaly, symptomatic epilepsy) syndrome. In 7 of the 21 families with a molecular diagnosis the pathogenic variants were only identified by clinical follow-up, manual reevaluation of the literature, a change of filter setting, and/or reconsideration of inheritance pattern. Most importantly, clinical implications included management changes in 8 cases and impact on family planning in 20 families with a molecular diagnosis. This study shows that reevaluation and follow-up can improve the diagnostic rate and that WES results have important implications on medical management and family planning. Furthermore, we could confirm STRADA as a gene associated with syndromic ID but find it questionable if the current designation as PMSE depicts the most important clinical features.

Movement disorder in GNAO1 encephalopathy associated with gain-of-function mutations

OBJECTIVE

To define molecular mechanisms underlying the clinical spectrum of epilepsy and movement disorder in individuals with de novo mutations in the GNAO1 gene.

METHODS

We identified all GNAO1 mutations reported in individuals with epilepsy (early infantile epileptiform encephalopathy 17) or movement disorders through April 2016; 15 de novo mutant alleles from 25 individuals were introduced into the Gα_o subunit by site-directed mutagenesis in a mammalian expression plasmid. We assessed protein expression and function in vitro in HEK-293T cells by Western blot and determined functional Gα_o-dependent cyclic adenosine monophosphate (cAMP) inhibition with a coexpressed α_2A adrenergic receptor.

RESULTS

Of the 15 clinical GNAO1 mutations studied, 9 show reduced expression and loss of function (LOF; <90% maximal inhibition). Six other mutations show variable levels of expression but exhibit normal or even gain-of-function (GOF) behavior, as demonstrated by significantly lower EC₅₀ values for α_2A adrenergic receptor-mediated inhibition of cAMP. The GNAO1 LOF mutations are associated with epileptic encephalopathy while GOF mutants (such as G42R, G203R, and E246K) or normally functioning mutants (R209) were found in patients with movement disorders with or without seizures.

CONCLUSIONS

Both LOF and GOF mutations in Gα_o (encoded by GNAO1) are associated with neurologic pathophysiology. There appears to be a strong predictive correlation between the in vitro biochemical phenotype and the clinical pattern of epilepsy vs movement disorder.

A case of severe movement disorder with GNAO1 mutation responsive to topiramate

We report the case of a 19-year-old female patient who had progressive chorea associated with a GNAO1 mutation. Chorea was refractory to multiple anticonvulsants, and the patient suffered from tiapride-induced neuroleptic malignant syndrome. After identification of a GNAO1 missense mutation at the age of 18years, topiramate treatment was initiated and the frequency of chorea decreased dramatically. The efficacy of topiramate may have been related to the inhibitory modulation of voltage-activated Ca²⁺ channels. Given the side effects and complications associated with neuroleptics and deep brain stimulation, respectively, topiramate is recommended for the first-line management of severe chorea associated with a GNAO1 mutation.

GNAO1 encephalopathy: Broadening the phenotype and evaluating treatment and outcome

OBJECTIVE

To describe better the motor phenotype, molecular genetic features, and clinical course of GNAO1-related disease.

METHODS

We reviewed clinical information, video recordings, and neuroimaging of a newly identified cohort of 7 patients with de novo missense and splice site GNAO1 mutations, detected by next-generation sequencing techniques.

RESULTS

Patients first presented in early childhood (median age of presentation 10 months, range 0-48 months), with a wide range of clinical symptoms ranging from severe motor and cognitive impairment with marked choreoathetosis, self-injurious behavior, and epileptic encephalopathy to a milder phenotype, featuring moderate developmental delay associated with complex stereotypies, mainly facial dyskinesia and mild epilepsy. Hyperkinetic movements were often exacerbated by specific triggers, such as voluntary movement, intercurrent illnesses, emotion, and high ambient temperature, leading to hospital admissions. Most patients were resistant to drug intervention, although tetrabenazine was effective in partially controlling dyskinesia for 2/7 patients. Emergency deep brain stimulation (DBS) was life saving in 1 patient, resulting in immediate clinical benefit with complete cessation of violent hyperkinetic movements. Five patients had well-controlled epilepsy and 1 had drug-resistant seizures. Structural brain abnormalities, including mild cerebral atrophy and corpus callosum dysgenesis, were evident in 5 patients. One patient had a diffuse astrocytoma (WHO grade II), surgically removed at age 16.

CONCLUSIONS

Our findings support the causative role of GNAO1 mutations in an expanded spectrum of early-onset epilepsy and movement disorders, frequently exacerbated by specific triggers and at times associated with self-injurious behavior. Tetrabenazine and DBS were the most useful treatments for dyskinesia.

Global inference of disease-causing single nucleotide variants from exome sequencing data

Background

Whole exome sequencing (WES) has recently emerged as an effective approach for identifying genetic variants underlying human diseases. However, considerable time and labour is needed for careful investigation of candidate variants. Although filtration based on population frequencies and functional prediction scores could effectively remove common and neutral variants, hundreds or even thousands of rare deleterious variants still remain. In addition, current WES platforms also provide variant information in flanking noncoding regions, such as promoters, introns and splice sites. Despite of being recognized to harbour causal variants, these regions are usually ignored by current analysis pipelines.

Results

We present a novel computational method, called Glints, to overcome the above limitations. Glints is capable of identifying disease-causing SNVs in both coding and flanking noncoding regions from exome sequencing data. The principle behind Glints is that disease-causing variants should manifest their effect at both variant and gene levels. Specifically, Glints integrates 14 types of functional scores, including predictions for both coding and noncoding variants, and 9 types of association scores, which help identifying disease relevant genes. We conducted a large-scale simulation studies based on 1000 Genomes Project data and demonstrated the effectiveness of our method in both coding and flanking noncoding regions. We also applied Glints in two real exome sequencing and demonstrated its effectiveness for uncovering disease-causing SNVs. Both standalone software and web server are available at our website http://bioinfo.au.tsinghua.edu.cn/jianglab/glints.

Conclusions

Glints is effective for uncovering disease-causing SNVs in coding and flanking noncoding regions, which is supported by both simulation and real case studies. Glints is expected to be a useful tool for human genetics research based on exome sequencing data.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-016-1325-x) contains supplementary material, which is available to authorized users.

Recurrent GNAO1 Mutations Associated With Developmental Delay and a Movement Disorder

In 2 unrelated patients with axial hypotonia, developmental delay and a hyperkinetic movement disorder, a missense mutation was found in codon 209 of the GNAO1 gene. From the still scarce literature on GNAO1 mutations, a clear genotype-phenotype correlation emerged. From the 26 patients reported thus far, 12 patients had epileptic encephalopathy, and 14 had a developmental delay and a hyperkinetic movement disorder. All but 1 of the latter patients had missense mutations in GNAO1 codon 209 or 246, which thus appear to be mutation hotspots. At least 2 sibling pairs showed that the recurrence risk after 1 affected child with a GNAO1 mutation might be relatively high (5-15%), due to apparent gonadal mosaicism in the parents.

Epileptic Encephalopathy in Childhood: A Stepwise Approach for Identification of Underlying Genetic Causes

Epilepsy is one of the most common neurological disorders in childhood. Epilepsy associated with global developmental delay and cognitive dysfunction is defined as epileptic encephalopathy. Certain inherited metabolic disorders presenting with epileptic encephalopathy can be treated with disease specific diet, vitamin, amino acid or cofactor supplementations. In those disorders, disease specific therapy is successful to achieve good seizure control and improve long-term neurodevelopmental outcome. For this reason, intractable epilepsy with global developmental delay or history of developmental regression warrants detailed metabolic investigations for the possibility of an underlying treatable inherited metabolic disorder, which should be undertaken as first line investigations. An underlying genetic etiology in epileptic encephalopathy has been supported by recent studies such as array comparative genomic hybridization, targeted next generation sequencing panels, whole exome and whole genome sequencing. These studies report a diagnostic yield up to 70%, depending on the applied genetic testing as well as number of patients enrolled. In patients with epileptic encephalopathy, a stepwise approach for diagnostic work-up will help to diagnose treatable inherited metabolic disorders quickly. Application of detailed genetic investigations such as targeted next generation sequencing as second line and whole exome sequencing as third line testing will diagnose underlying genetic disease which will help for genetic counseling as well as guide for prenatal diagnosis. Knowledge of underlying genetic cause will provide novel insights into the pathogenesis of epileptic encephalopathy and pave the ground towards the development of targeted neuroprotective treatment strategies to improve the health outcome of children with epileptic encephalopathy.

Recent advances in genetics of chorea

PURPOSE OF REVIEW

Chorea presenting in childhood and adulthood encompasses several neurological disorders, both degenerative and nonprogressive, often with a genetic basis. In this review, we discuss how modern genomic technologies are expanding our knowledge of monogenic choreic syndromes and advancing our insight into the molecular mechanisms responsible for chorea.

RECENT FINDINGS

A genome-wide association study in Huntington's disease identified genetic disease modifiers involved in controlling DNA repair mechanisms and stability of the HTT trinucleotide repeat expansion. Chorea is the cardinal feature of newly recognized genetic entities, ADCY5 and PDE10A-related choreas, with onset in infancy and childhood. A phenotypic overlap between chorea, ataxia, epilepsy, and neurodevelopmental disorders is becoming increasingly evident.

SUMMARY

The differential diagnosis of genetic conditions presenting with chorea has considerably widened, permitting a molecular diagnosis and an improved prognostic definition in an expanding number of cases. The identification of Huntington's disease genetic modifiers and new chorea-causing gene mutations has allowed the initial recognition of converging molecular pathways underlying medium spiny neurons degeneration and dysregulation of normal development and activity of basal ganglia circuits. Signalling downstream of dopamine receptors and control of cAMP levels represent a very promising target for the development of new aetiology-based treatments for chorea and other hyperkinetic disorders.

Clinical Course of Six Children With GNAO1 Mutations Causing a Severe and Distinctive Movement Disorder

OBJECTIVES

Mutations in GNAO1 have been described in 11 patients to date. Although most of these individuals had epileptic encephalopathy, four patients had a severe movement disorder as the prominent feature. We describe the largest series of patients with de novoGNAO1 mutations who have severe chorea, developmental delay, and hypotonia in the absence of epilepsy.

METHODS

Six patients with recurrent missense mutations in GNAO1 as detected by whole exome sequencing were identified at three institutions. We describe the presentation, clinical course, and response to treatment of these patients.

RESULTS

All six patients exhibited global developmental delay and hypotonia from infancy. Chorea developed by age four years in all but one patient, who developed chorea at 14 years. Treatments with neuroleptics and tetrabenazine were most effective in the baseline management of chorea. The chorea became gradually progressive and marked by episodes of severe, refractory ballismus requiring intensive care unit admissions in four of six patients. Exacerbations indirectly led to the death of two patients.

CONCLUSIONS

Patients with GNAO1 mutations can present with a severe, progressive movement disorder in the absence of epilepsy. Exacerbations may be refractory to treatment and can result in life-threatening secondary complications. Early and aggressive treatment of these exacerbations with direct admission to intensive care units for treatment with anesthetic drips may prevent some secondary complications. However the chorea and ballismus can be refractory to maximum medical therapy.

GNAO1 encephalopathy: further delineation of a severe neurodevelopmental syndrome affecting females

Background

De novo heterozygous mutations in the GNAO1 gene, encoding the Gα o subunit of G-proteins, are the cause of a severe neurodevelopmental disorder, featuring early infantile seizures, profound cognitive dysfunction and, occasionally, movement disorder (early infantile epileptic encephalopathy-17).

Methods

We report a further case of this association in a 20 month-old Spanish girl with neonatal-onset refractory seizures, progressive microcephaly, oral-lingual dyskinesia and nearly absent psychomotor development. We performed whole-exome sequencing, a computational structural analysis of the novel gene variant identified and reviewed the previously reported cases.

Results

Trio whole-exome-sequencing uncovered a de novo p.Leu199Pro GNAO1 mutation. Computational structural analysis indicates this novel variant adversely affects the stability of the G-protein heterotrimeric complex as a whole. Of note, our patient showed a sustained seizure reduction while on a ketogenic diet.

Conclusions

With this observation, a total of twelve patients with GNAO1 encephalopathy have been reported. Oral-lingual dyskinesia and responsiveness of seizures to ketogenic diet are novel features. The distorted sex ratio (12/12 females) of the condition remains unexplained; a differential gender effect of the disruption of G-protein- mediated signal transduction on the developing brain can be hypothesized.

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-016-0416-0) contains supplementary material, which is available to authorized users.

PCDH19-related epileptic encephalopathy in a male mosaic for a truncating variant

Variants in the X-linked gene PCDH19 are associated with early infantile epileptic encephalopathy-9. This unusual condition spares hemizygous males except for psychiatric and behavioral abnormalities, and for this reason is also known as female limited epilepsy. Some cases are due to de novo PCDH19 variants, but may also be paternally inherited. Our patient is a 6-year-old male with epileptic encephalopathy. Exome sequencing revealed apparent heterozygosity in PCDH19 for a novel nonsense variant, c.605C>A (p.Ser202*), inconsistent with expectations for a male. Testing of other tissues revealed a mixture of mutant and normal alleles. These results are consistent with somatic mosaicism for p.Ser202*. This is the second male with somatic mosaicism for PCDH19 deficiency, providing further support for cellular interference as the pathogenic mechanism for this condition, which leads to this unusual mode of inheritance in which females are more severely affected than males. © 2016 Wiley Periodicals, Inc.