The phenotypic spectrum of WWOX-related disorders: 20 additional cases of WOREE syndrome and review of the literature

Case report: Adult patient with WWOX developmental and epileptic encephalopathy: 40 years of observation

WWOX developmental and epileptic encephalopathy is characterised by drug-resistant epilepsy with onset within the first year of life and severe psychomotor developmental delay. This report presents for the first time a clinical case of an adult patient with a homozygous likely pathogenic variant (p.Thr12Met) in the WWOX gene, with more than 40 years of follow-up. The patient had refractory epilepsy with various types of seizures during his life: mainly epileptic spasms, autonomic, myoclonic, tonic seizures, and absences. The patient had a prominent developmental delay with a lack of expressive speech, but by the age of 3, he had acquired the skills to sit, crawl, and walk with support. In adolescence, there was an acute regression of acquired skills to a total absence of independent motor activity. The patient had dysmorphic features, such as upslanting palpebral fissures, arched eyebrows, and hypertelorism. For many years, the patient was given a diagnosis of cerebral palsy; 38 years after the onset of the disease, he was given a molecular genetic diagnosis of WWOX-associated developmental and epileptic encephalopathy. Our observation illustrates the natural history of WWOX-DEE and the high clinical significance of early genetic diagnostics for identifying the cause of developmental delay and resistant epilepsy.

WWOX-related epileptic encephalopathy caused by a novel mutation in the WWOX gene: a case report

Background

WWOX-related epileptic encephalopathy is an autosomal recessive disorder caused by mutations in the WW-containing oxidoreductase gene, characterized by the onset of refractory seizures in infants. Early-onset epilepsy, electroencephalography abnormalities, and developmental delay or degeneration are the main clinical manifestations. Early death can occur in severe cases. In the present study, a novel variant in WWOX was detected in a patient with epilepsy and his healthy parents.

Case presentation

A 5-month-old boy presented with epilepsy. The main manifestations were intractable seizures, mental and motor retardation and hearing impairment. Subsequent genetic testing revealed the presence of an epilepsy-associated novel mutation: c.991C>A (amino acid change: p.Ser304Tyr) in the WWOX gene. Variants were inherited from parents with healthy phenotypes. Finally, a patient died at 6 months of age.

Conclusion

The discovery of novel variants has enriched the existing database of WWOX gene variants and may expand the range of clinical options for treating WWOX-related disorders.

Developmental epileptic encephalopathy caused by homozygosity of a c.172+1G>C variant in the WWOX gene

BACKGROUND

Variations in the WWOX gene have been identified as the leading cause of several central nervous system disorders. However, most previous reports have focused on the description of clinical phenotype, neglecting functional verification. Herein, we presented a case of a patient with developmental epileptic encephalopathy (DEE) caused by WWOX gene variation.

CASE PRESENTATION

Our patient was a 13-month-old girl with abnormal facial features, including facial hypotonia, arched eyebrows, a broad nose, and a depressed nasal bridge. She also had sparse and yellow hair, a low anterior hairline, and a short neck. Before the age of 8 months, she was suffering from mild seizures. Her developmental delay gradually worsened, and she suffered infantile spasms. After treatment with vigabatrin, seizures subsided. WWOX gene homozygous variation c.172+1G>C was identified using whole exome sequencing. Further minigene assay confirmed that the variation site affected splicing, causing protein truncation and affecting its function.

CONCLUSION

Clinical phenotype and minigene results suggest that WWOX gene homozygous variation c.172+1G>C can cause severe DEE. We also concluded that vigabatrin can effectively treat seizures.

Identification of a novel splice-site WWOX variant with paternal uniparental isodisomy in a patient with infantile epileptic encephalopathy

WOREE syndrome is an early infantile epileptic encephalopathy characterized by drug-resistant seizures and severe psychomotor developmental delays. We report a case of a WWOX splice-site mutation with uniparental isodisomy. A 1-year and 7-month-old girl presented with nystagmus and epileptic seizures from early infancy, with no fixation or pursuit of vision. Physical examination revealed small deformities, such as swelling of both cheeks, folded fingers, rocking feet, and scoliosis. Brain imaging revealed slight hypoplasia of the cerebrum. Electroencephalogram showed focal paroxysmal discharges during the interictal phase of seizures. Vitamin B6 and zonisamide were administered for early infantile epileptic encephalopathy; however, the seizures were not relieved. Despite altering the type and dosage of antiepileptic drugs and ACTH therapy, the seizures were intractable. Whole-exome analysis revealed the homozygosity of WWOX(NM_016373.4):c.516+1G>A. The WWOX mRNA sequencing using peripheral blood RNA confirmed that exon 5 was homozygously deleted. Based on these results, the patient was diagnosed with WOREE syndrome at 5 months. The WWOX variant found in this study is novel and has never been reported before. WOREE syndrome being extremely rare, further case series and analyses of its pathophysiology are warranted.

Limbic-predominant age-related TDP-43 encephalopathy (LATE-NC): Co-pathologies and genetic risk factors provide clues about pathogenesis

Limbic-predominant age-related TDP-43 encephalopathy neuropathologic change (LATE-NC) is detectable at autopsy in more than one-third of people beyond age 85 years and is robustly associated with dementia independent of other pathologies. Although LATE-NC has a large impact on public health, there remain uncertainties about the underlying biologic mechanisms. Here, we review the literature from human studies that may shed light on pathogenetic mechanisms. It is increasingly clear that certain combinations of pathologic changes tend to coexist in aging brains. Although "pure" LATE-NC is not rare, LATE-NC often coexists in the same brains with Alzheimer disease neuropathologic change, brain arteriolosclerosis, hippocampal sclerosis of aging, and/or age-related tau astrogliopathy (ARTAG). The patterns of pathologic comorbidities provide circumstantial evidence of mechanistic interactions ("synergies") between the pathologies, and also suggest common upstream influences. As to primary mediators of vulnerability to neuropathologic changes, genetics may play key roles. Genes associated with LATE-NC include TMEM106B, GRN, APOE, SORL1, ABCC9, and others. Although the anatomic distribution of TDP-43 pathology defines the condition, important cofactors for LATE-NC may include Tau pathology, endolysosomal pathways, and blood-brain barrier dysfunction. A review of the human phenomenology offers insights into disease-driving mechanisms, and may provide clues for diagnostic and therapeutic targets.

Behavioral as well as hippocampal transcriptomic and microglial responses differ across sexes in adult mouse offspring exposed to a dual genetic and environmental challenge

INTRODUCTION

A wide range of positive, negative, and cognitive symptoms compose the clinical presentation of schizophrenia. Schizophrenia is a multifactorial disorder in which genetic and environmental risk factors interact for a full emergence of the disorder. Infectious challenges during pregnancy are a well-known environmental risk factor for schizophrenia. Also, genetic variants affecting the function of fractalkine signaling between neurons and microglia were linked to schizophrenia. Translational animal models recapitulating these complex gene-environment associations have a great potential to untangle schizophrenia neurobiology and propose new therapeutic strategies.

METHODS

Given that genetic variants affecting the function of fractalkine signaling between neurons and microglia were linked to schizophrenia, we compared the outcomes of a well-characterized model of maternal immune activation induced using the viral mimetic polyinosinic:polycytidylic acid (Poly I:C) in wild-type versus fractalkine receptor knockout mice. Possible behavioral and immune alterations were assessed in male and female offspring during adulthood. Considering the role of the hippocampus in schizophrenia, microglial analyses and bulk RNA sequencing were performed within this region to assess the neuroimmune dynamics at play. Males and females were examined separately.

RESULTS

Offspring exposed to the dual challenge paradigm exhibited symptoms relevant to schizophrenia and unpredictably to mood disorders. Males displayed social and cognitive deficits related to schizophrenia, while females mainly presented anxiety-like behaviors related to mood disorders. Hippocampal microglia in females exposed to the dual challenge were hypertrophic, indicative of an increased surveillance, whereas those in males showed on the other end of the spectrum blunted morphologies with a reduced phagocytosis. Hippocampal bulk-RNA sequencing further revealed a downregulation in females of genes related to GABAergic transmission, which represents one of the main proposed causes of mood disorders.

CONCLUSIONS

Building on previous results, we identified in the current study distinctive behavioral phenotypes in female mice exposed to a dual genetic and environmental challenge, thus proposing a new model of neurodevelopmentally-associated mood and affective symptoms. This paves the way to future sex-specific investigations into the susceptibility to developmental challenges using animal models based on genetic and immune vulnerability as presented here.

Neuroimaging features of WOREE syndrome: a mini-review of the literature

The WWOX gene encodes a 414-amino-acid protein composed of two N-terminal WW domains and a C-terminal short-chain dehydrogenase/reductase (SDR) domain. WWOX protein is highly conserved among species and mainly expressed in the cerebellum, cerebral cortex, brain stem, thyroid, hypophysis, and reproductive organs. It plays a crucial role in the biology of the central nervous system, and it is involved in neuronal development, migration, and proliferation. Biallelic pathogenic variants in WWOX have been associated with an early infantile epileptic encephalopathy known as WOREE syndrome. Both missense and null variants have been described in affected patients, leading to a reduction in protein function and stability. The most severe WOREE phenotypes have been related to biallelic null/null variants, associated with the complete loss of function of the protein. All affected patients showed brain anomalies on magnetic resonance imaging (MRI), suggesting the pivotal role of WWOX protein in brain homeostasis and developmental processes. We provided a literature review, exploring both the clinical and radiological spectrum related to WWOX pathogenic variants, described to date. We focused on neuroradiological findings to better delineate the WOREE phenotype with diagnostic and prognostic implications.

Identification of compound heterozygous deletion of the WWOX gene in WOREE syndrome

BACKGROUND

Biallelic loss-of-function variants in WWOX cause WWOX-related epileptic encephalopathy (WOREE syndrome), which has been reported in 60 affected individuals to date. In this study, we report on an affected individual with WOREE syndrome who presented with early-onset refractory seizures and global neurodevelopmental delay and died at the age of two and a half years.

METHODS

We present clinical and molecular findings in the affected individual, including biallelic pathogenic variants in the WWOX gene. We employed different molecular approaches, such as whole exome sequencing, quantitative real-time polymerase chain reaction (qPCR), and whole-genome sequencing, to identify the genetic variants. The breakpoints were determined through gap PCR and Sanger sequencing.

RESULT

Whole exome sequencing revealed homozygous exon 6 deletion in the WWOX gene in the proband. Quantitative real-time PCR confirmed that the parents were heterozygous carriers of exon 6 deletion. However, using whole-genome sequencing, we identified three larger deletions (maternal allele with exon 6-8 deletion and paternal allele with two deletions in proximity one in intron 5 and the other in exon 6) involving the WWOX gene in the proband, with deletion sizes of 13,261 bp, 53,904 bp, and 177,200 bp. The exact breakpoints were confirmed through gap PCR and Sanger sequencing. We found that the proband inherited the discontinuous deletion of intron 5 and exon 6 from the father, and the exons 6-8 deletion from the mother using gap PCR.

CONCLUSION

Our findings extend the variant spectrum of WOREE syndrome and support the critical role of the WWOX gene in neural development.

Structural and non-coding variants increase the diagnostic yield of clinical whole genome sequencing for rare diseases

BACKGROUND

Whole genome sequencing is increasingly being used for the diagnosis of patients with rare diseases. However, the diagnostic yields of many studies, particularly those conducted in a healthcare setting, are often disappointingly low, at 25-30%. This is in part because although entire genomes are sequenced, analysis is often confined to in silico gene panels or coding regions of the genome.

METHODS

We undertook WGS on a cohort of 122 unrelated rare disease patients and their relatives (300 genomes) who had been pre-screened by gene panels or arrays. Patients were recruited from a broad spectrum of clinical specialties. We applied a bioinformatics pipeline that would allow comprehensive analysis of all variant types. We combined established bioinformatics tools for phenotypic and genomic analysis with our novel algorithms (SVRare, ALTSPLICE and GREEN-DB) to detect and annotate structural, splice site and non-coding variants.

RESULTS

Our diagnostic yield was 43/122 cases (35%), although 47/122 cases (39%) were considered solved when considering novel candidate genes with supporting functional data into account. Structural, splice site and deep intronic variants contributed to 20/47 (43%) of our solved cases. Five genes that are novel, or were novel at the time of discovery, were identified, whilst a further three genes are putative novel disease genes with evidence of causality. We identified variants of uncertain significance in a further fourteen candidate genes. The phenotypic spectrum associated with RMND1 was expanded to include polymicrogyria. Two patients with secondary findings in FBN1 and KCNQ1 were confirmed to have previously unidentified Marfan and long QT syndromes, respectively, and were referred for further clinical interventions. Clinical diagnoses were changed in six patients and treatment adjustments made for eight individuals, which for five patients was considered life-saving.

CONCLUSIONS

Genome sequencing is increasingly being considered as a first-line genetic test in routine clinical settings and can make a substantial contribution to rapidly identifying a causal aetiology for many patients, shortening their diagnostic odyssey. We have demonstrated that structural, splice site and intronic variants make a significant contribution to diagnostic yield and that comprehensive analysis of the entire genome is essential to maximise the value of clinical genome sequencing.

Redefining cerebral palsies as a diverse group of neurodevelopmental disorders with genetic aetiology

Cerebral palsy is a clinical descriptor covering a diverse group of permanent, non-degenerative disorders of motor function. Around one-third of cases have now been shown to have an underlying genetic aetiology, with the genetic landscape overlapping with those of neurodevelopmental disorders including intellectual disability, epilepsy, speech and language disorders and autism. Here we review the current state of genomic testing in cerebral palsy, highlighting the benefits for personalized medicine and the imperative to consider aetiology during clinical diagnosis. With earlier clinical diagnosis now possible, we emphasize the opportunity for comprehensive and early genomic testing as a crucial component of the routine diagnostic work-up in people with cerebral palsy.

BRAT1-related disorders: phenotypic spectrum and phenotype-genotype correlations from 97 patients

BRAT1 biallelic variants are associated with rigidity and multifocal seizure syndrome, lethal neonatal (RMFSL), and neurodevelopmental disorder associating cerebellar atrophy with or without seizures syndrome (NEDCAS). To date, forty individuals have been reported in the literature. We collected clinical and molecular data from 57 additional cases allowing us to study a large cohort of 97 individuals and draw phenotype-genotype correlations. Fifty-nine individuals presented with BRAT1-related RMFSL phenotype. Most of them had no psychomotor acquisition (100%), epilepsy (100%), microcephaly (91%), limb rigidity (93%), and died prematurely (93%). Thirty-eight individuals presented a non-lethal phenotype of BRAT1-related NEDCAS phenotype. Seventy-six percent of the patients in this group were able to walk and 68% were able to say at least a few words. Most of them had cerebellar ataxia (82%), axial hypotonia (79%) and cerebellar atrophy (100%). Genotype-phenotype correlations in our cohort revealed that biallelic nonsense, frameshift or inframe deletion/insertion variants result in the severe BRAT1-related RMFSL phenotype (46/46; 100%). In contrast, genotypes with at least one missense were more likely associated with NEDCAS (28/34; 82%). The phenotype of patients carrying splice variants was variable: 41% presented with RMFSL (7/17) and 59% with NEDCAS (10/17).

Whole-Genome Sequencing Among Kazakhstani Children with Early-Onset Epilepsy Revealed New Gene Variants and Phenotypic Variability

In Kazakhstan, there is insufficient data on genetic epilepsy, which has its own clinical and management implications. Thus, this study aimed to use whole genome sequencing to identify and evaluate genetic variants and genetic structure of early onset epilepsy in the Kazakhstani pediatric population. In this study, for the first time in Kazakhstan, whole genome sequencing was carried out among epilepsy diagnosed children. The study involved 20 pediatric patients with early onset epilepsy and no established cause of the disease during the July-December, 2021. The average age at enrolment was 34.5 months, with a mean age at seizure onset of 6 months. Six patients (30%) were male, and 7 were familial cases. We identified pathogenic and likely pathogenic variants in 14 (70%) cases, among them, 6 novel disease gene variants (KCNQ2, CASK, WWOX, MT-CO3, GRIN2D, and SLC12A5). Other genes associated with the disease were SCN1A (x2), SLC2A1, ARX, CACNA1B, PCDH19, KCNT1, and CHRNA2. Identification of the genetic causes in 70% of cases confirms the general structure of the etiology of early onset epilepsy and the necessity of using NGS in diagnostics. Moreover, the study describes new genotype-phenotypic correlations in genetic epilepsy. Despite certain limitations of the study, it can be concluded that the genetic etiology of pediatric epilepsy in Kazakhstan is very broad and requires further research.

WWOX developmental and epileptic encephalopathy: Understanding the epileptology and the mortality risk

OBJECTIVE

WWOX is an autosomal recessive cause of early infantile developmental and epileptic encephalopathy (WWOX-DEE), also known as WOREE (WWOX-related epileptic encephalopathy). We analyzed the epileptology and imaging features of WWOX-DEE, and investigated genotype-phenotype correlations, particularly with regard to survival.

METHODS

We studied 13 patients from 12 families with WWOX-DEE. Information regarding seizure semiology, comorbidities, facial dysmorphisms, and disease outcome were collected. Electroencephalographic (EEG) and brain magnetic resonance imaging (MRI) data were analyzed. Pathogenic WWOX variants from our cohort and the literature were coded as either null or missense, allowing individuals to be classified into one of three genotype classes: (1) null/null, (2) null/missense, (3) missense/missense. Differences in survival outcome were estimated using the Kaplan-Meier method.

RESULTS

All patients experienced multiple seizure types (median onset = 5 weeks, range = 1 day-10 months), the most frequent being focal (85%), epileptic spasms (77%), and tonic seizures (69%). Ictal EEG recordings in six of 13 patients showed tonic (n = 5), myoclonic (n = 2), epileptic spasms (n = 2), focal (n = 1), and migrating focal (n = 1) seizures. Interictal EEGs demonstrated slow background activity with multifocal discharges, predominantly over frontal or temporo-occipital regions. Eleven of 13 patients had a movement disorder, most frequently dystonia. Brain MRIs revealed severe frontotemporal, hippocampal, and optic atrophy, thin corpus callosum, and white matter signal abnormalities. Pathogenic variants were located throughout WWOX and comprised both missense and null changes including five copy number variants (four deletions, one duplication). Survival analyses showed that patients with two null variants are at higher mortality risk (p-value = .0085, log-rank test).

SIGNIFICANCE

Biallelic WWOX pathogenic variants cause an early infantile developmental and epileptic encephalopathy syndrome. The most common seizure types are focal seizures and epileptic spasms. Mortality risk is associated with mutation type; patients with biallelic null WWOX pathogenic variants have significantly lower survival probability compared to those carrying at least one presumed hypomorphic missense pathogenic variant.

WWOX P47T partial loss-of-function mutation induces epilepsy, progressive neuroinflammation, and cerebellar degeneration in mice phenocopying human SCAR12

WWOX gene loss-of-function (LoF) has been associated with neuropathologies resulting in developmental, epileptic, and ataxic phenotypes of varying severity based on the level of WWOX dysfunction. WWOX gene biallelic germline variant p.Pro47Thr (P47T) has been causally associated with a new form of autosomal recessive cerebellar ataxia with epilepsy and intellectual disability (SCAR12, MIM:614322). This mutation affecting the WW1 protein binding domain of WWOX, impairs its interaction with canonical proline-proline-X-tyrosine motifs in partner proteins. We generated a mutant knock-in mouse model of Wwox P47T mutation that phenocopies human SCAR12. WwoxP47T/P47T mice displayed epilepsy, profound social behavior and cognition deficits, and poor motor coordination, and unlike KO models that survive only for 1 month, live beyond 1 year of age. These deficits progressed with age and mice became practically immobile, suggesting severe cerebellar dysfunction. WwoxP47T/P47T mice brains revealed signs of progressive neuroinflammation with elevated astro-microgliosis that increased with age. Cerebellar cortex displayed significantly reduced molecular and granular layer thickness and a strikingly reduced number of Purkinje cells with degenerated dendrites. Transcriptome profiling from various brain regions of WW domain LoF mice highlighted widespread changes in neuronal and glial pathways, enrichment of bioprocesses related to neuroinflammation, and severe cerebellar dysfunction. Our results show significant pathobiological effects and potential mechanisms through which WWOX partial LoF leads to epilepsy, cerebellar neurodegeneration, neuroinflammation, and ataxia. Additionally, the mouse model described here will be a useful tool to understand the role of WWOX in common neurodegenerative conditions in which this gene has been identified as a novel risk factor.

Expansion of the clinical and molecular spectrum of WWOX-related epileptic encephalopathy

WWOX biallelic loss-of-function pathogenic single nucleotide variants (SNVs) and copy number variants (CNVs) including exonic deletions and duplications cause WWOX-related epileptic encephalopathy (WOREE) syndrome. This disorder is characterized by refractory epilepsy, axial hypotonia, peripheral hypertonia, progressive microcephaly, and premature death. Here we report five patients with WWOX biallelic predicted null variants identified by exome sequencing (ES), genome sequencing (GS), and/or chromosomal microarray analysis (CMA). SNVs and intragenic deletions of one or more exons were commonly reported in WOREE syndrome patients which made the genetic diagnosis challenging and required a combination of different diagnostic technologies. These patients presented with severe, developmental and epileptic encephalopathy (DEE), and other cardinal features consistent with WOREE syndrome. This report expands the clinical phenotype associated with this condition, including failure to thrive in most patients and epilepsy that responded to a ketogenic diet in three patients. Dysmorphic features and abnormal prenatal findings were not commonly observed. Additionally, recurrent pancreatitis and sensorineural hearing loss each were observed in single patients. In summary, these phenotypic features broaden the clinical spectrum of WOREE syndrome.

WWOX and metabolic regulation in normal and pathological conditions

WW domain-containing oxidoreductase (WWOX) spans the common fragile site FRA16D. There is evidence that translocations and deletions affecting WWOX accompanied by loss of expression are frequent in many cancers and often correlate with a worse prognosis. Additionally, WWOX germline mutations were also found to be the cause of pathologies of brain development. Because WWOX binds to some transcription factors, it is a modulator of many cellular processes, including metabolic processes. Recently, studies have linked WWOX to familial dyslipidemias, osteopenia, metabolic syndrome, and gestational diabetes, confirming its role as a regulator of steroid, cholesterol, glucose, and normal bone metabolism. The WW domain of WWOX is directly engaged in the control of the activity of transcription factors such as HIF1α and RUNX2; therefore, WWOX gene alterations are associated with some metabolic abnormalities. Presently, most interest is devoted to the associations between WWOX and glucose and basic energy metabolism disturbances. In particular, its involvement in the initiation of the Warburg effect in cancer or gestational diabetes and type II diabetes is of interest. This review is aimed at systematically and comprehensively presenting the current state of knowledge about the participation of WWOX in the metabolism of healthy and diseased organisms.

A Phenotypic-Driven Approach for the Diagnosis of WOREE Syndrome

BACKGROUND

WOREE syndrome is a rare neurodevelopmental disorder featuring drug-resistant epilepsy and global developmental delay. The disease, caused by biallelic pathogenic variants in the WWOX gene, usually leads to severe disability or death within the first years of life. Clinicians have become more confident with the phenotypic picture of WOREE syndrome, allowing earlier clinical diagnosis. We report a boy with a peculiar clinic-radiological pattern supporting the diagnosis of WOREE syndrome.

METHODS

DNA was extracted from blood samples of the proband and his parents and subjected to Exome Sequencing (ES). Agarose gel electrophoresis, real-time quantitative PCR (Q-PCR), and array-CGH 180K were also performed.

RESULTS

ES detected a pathogenic stop variant (c.790C > T, p.Arg264*) in one allele of WWOX in the proband and his unaffected mother. A 180K array-CGH analysis revealed a 84,828-bp (g.chr16:78,360,803-78,445,630) deletion encompassing exon 6. The Q-PCR product showed that the proband and his father harbored the same deleted fragment, fusing exons 5 and 7 of WWOX.

CONCLUSIONS

Genetic testing remains crucial in establishing the definitive diagnosis of WOREE syndrome and allows prenatal interventions/parental counseling. However, our findings suggest that targeted Next Generation Sequencing-based testing may occasionally show technical pitfalls, prompting further genetic investigation in selected cases with high clinical suspicion.

Neonatal neuronal WWOX gene therapy rescues Wwox null phenotypes

WW domain-containing oxidoreductase (WWOX) is an emerging neural gene-regulating homeostasis of the central nervous system. Germline biallelic mutations in WWOX cause WWOX-related epileptic encephalopathy (WOREE) syndrome and spinocerebellar ataxia and autosomal recessive 12 (SCAR12), two devastating neurodevelopmental disorders with highly heterogenous clinical outcomes, the most common being severe epileptic encephalopathy and profound global developmental delay. We recently demonstrated that neuronal ablation of murine Wwox recapitulates phenotypes of Wwox-null mice leading to intractable epilepsy, hypomyelination, and postnatal lethality. Here, we designed and produced an adeno-associated viral vector (AAV9) harboring murine Wwox or human WWOX cDNA and driven by the human neuronal Synapsin I promoter (AAV-SynI-WWOX). Testing the efficacy of AAV-SynI-WWOX delivery in Wwox-null mice demonstrated that specific neuronal restoration of WWOX expression rescued brain hyperexcitability and seizures, hypoglycemia, myelination deficits, and the premature lethality and behavioral deficits of Wwox-null mice. These findings provide a proof-of-concept for WWOX gene therapy as a promising approach to curing children with WOREE and SCAR12.

Altered neocortical oscillations and cellular excitability in an in vitro Wwox knockout mouse model of epileptic encephalopathy

Loss of function mutations of the WW domain-containing oxidoreductase (WWOX) gene are associated with severe and fatal drug-resistant pediatric epileptic encephalopathy. Epileptic seizures are typically characterized by neuronal hyperexcitability; however, the specific contribution of WWOX to that hyperexcitability has yet to be investigated. Using a mouse model of neuronal Wwox-deletion that exhibit spontaneous seizures, in vitro whole-cell and field potential electrophysiological characterization identified spontaneous bursting activity in the neocortex, a marker of the underlying network hyperexcitability. Spectral analysis of the neocortical bursting events highlighted increased phase-amplitude coupling, and a propagation from layer II/III to layer V. These bursts were NMDAR and gap junction dependent. In layer II/III pyramidal neurons, Wwox knockout mice demonstrated elevated amplitude of excitatory post-synaptic currents, whereas the frequency and amplitude of inhibitory post-synaptic currents were reduced, as compared to heterozygote and wild-type littermate controls. Furthermore, these neurons were depolarized and demonstrated increased action potential frequency, sag current, and post-inhibitory rebound. These findings suggest WWOX plays an essential role in balancing neocortical excitability and provide insight towards developing therapeutics for those suffering from WWOX disorders.

Diagnostic yield of microarrays in individuals with non-syndromic developmental delay and intellectual disability

BACKGROUND

Intellectual disability (ID), or developmental delay (DD) when the individual is yet under 5 years of age, is evident before 18 years of age and is characterised by significant limitations in both intellectual functioning and adaptive behaviour. ID/DD may be clinically classified as syndromic or non-syndromic. Genomic copy number variations (CNVs) constitute a well-established aetiological subgroup of ID/DD. Overall diagnostic yield of microarrays is estimated at 10-25% for ID/DD, especially higher when particular clinical features that render the condition syndromic accompany.

METHODS

In this study, we aimed to investigate the diagnostic yield of microarrays in the subgroup of individuals with non-syndromic ID/DD (NSID/NSDD). A total of 302 NSID/NSDD individuals who have undergone microarray analysis between October 2013 and April 2020 were included. Accompanying clinical data, including head circumference, delayed developmental areas, seizures and behavioural problems were collected and analysed separately in NSID and NSDD subgroups.

RESULTS

The diagnostic yield of microarray analyses in NSID/NSDD was determined as 10.9% in NSID (10.7%) and in NSDD (11.1%). Presence of behavioural and epileptic problems did not contribute to the diagnostic yield. However, in the presence of macrocephaly, the contribution to diagnostic yield was statistically significant particularly in NSDD group. The most common pathogenic CNVs involved chromosomes 16, 15 and X. Lastly, we propose a Xq21.32q22.1 deletion as likely pathogenic in a child with isolated language delay and accompanying seizures.

CONCLUSIONS

Particularly in neurodevelopmental diseases, microarrays are useful for establishing the diagnosis and detecting novel susceptibility regions. Future studies would accurately classify the herein presented variants of uncertain significance CNVs as pathogenic or benign.

WWOX-Related Neurodevelopmental Disorders: Models and Future Perspectives

The WW domain-containing oxidoreductase (WWOX) gene was originally discovered as a putative tumor suppressor spanning the common fragile site FRA16D, but as time has progressed the extent of its pleiotropic function has become apparent. At present, WWOX is a major source of interest in the context of neurological disorders, and more specifically developmental and epileptic encephalopathies (DEEs). This review article aims to introduce the many model systems used through the years to study its function and roles in neuropathies. Similarities and fundamental differences between rodent and human models are discussed. Finally, future perspectives and promising research avenues are suggested.

Modeling genetic epileptic encephalopathies using brain organoids

Developmental and epileptic encephalopathies (DEE) are a group of disorders associated with intractable seizures, brain development, and functional abnormalities, and in some cases, premature death. Pathogenic human germline biallelic mutations in tumor suppressor WW domain-containing oxidoreductase (WWOX) are associated with a relatively mild autosomal recessive spinocerebellar ataxia-12 (SCAR12) and a more severe early infantile WWOX-related epileptic encephalopathy (WOREE). In this study, we generated an in vitro model for DEEs, using the devastating WOREE syndrome as a prototype, by establishing brain organoids from CRISPR-engineered human ES cells and from patient-derived iPSCs. Using these models, we discovered dramatic cellular and molecular CNS abnormalities, including neural population changes, cortical differentiation malfunctions, and Wnt pathway and DNA damage response impairment. Furthermore, we provide a proof of concept that ectopic WWOX expression could potentially rescue these phenotypes. Our findings underscore the utility of modeling childhood epileptic encephalopathies using brain organoids and their use as a unique platform to test possible therapeutic intervention strategies.

Molecular Biology of the WWOX Gene That Spans Chromosomal Fragile Site FRA16D

It is now more than 20 years since the FRA16D common chromosomal fragile site was characterised and the WWOX gene spanning this site was identified. In this time, much information has been discovered about its contribution to disease; however, the normal biological role of WWOX is not yet clear. Experiments leading to the identification of the WWOX gene are recounted, revealing enigmatic relationships between the fragile site, its gene and the encoded protein. We also highlight research mainly using the genetically tractable model organism Drosophila melanogaster that has shed light on the integral role of WWOX in metabolism. In addition to this role, there are some particularly outstanding questions that remain regarding WWOX, its gene and its chromosomal location. This review, therefore, also aims to highlight two unanswered questions. Firstly, what is the biological relationship between the WWOX gene and the FRA16D common chromosomal fragile site that is located within one of its very large introns? Secondly, what is the actual substrate and product of the WWOX enzyme activity? It is likely that understanding the normal role of WWOX and its relationship to chromosomal fragility are necessary in order to understand how the perturbation of these normal roles results in disease.

Normal cells repel WWOX-negative or -dysfunctional cancer cells via WWOX cell surface epitope 286-299

Metastatic cancer cells are frequently deficient in WWOX protein or express dysfunctional WWOX (designated WWOXd). Here, we determined that functional WWOX-expressing (WWOXf) cells migrate collectively and expel the individually migrating WWOXd cells. For return, WWOXd cells induces apoptosis of WWOXf cells from a remote distance. Survival of WWOXd from the cell-to-cell encounter is due to activation of the survival IκBα/ERK/WWOX signaling. Mechanistically, cell surface epitope WWOX286-299 (repl) in WWOXf repels the invading WWOXd to undergo retrograde migration. However, when epitope WWOX7-21 (gre) is exposed, WWOXf greets WWOXd to migrate forward for merge. WWOX binds membrane type II TGFβ receptor (TβRII), and TβRII IgG-pretreated WWOXf greet WWOXd to migrate forward and merge with each other. In contrast, TβRII IgG-pretreated WWOXd loses recognition by WWOXf, and WWOXf mediates apoptosis of WWOXd. The observatons suggest that normal cells can be activated to attack metastatic cancer cells. WWOXd cells are less efficient in generating Ca²⁺ influx and undergo non-apoptotic explosion in response to UV irradiation in room temperature. WWOXf cells exhibit bubbling cell death and Ca²⁺ influx effectively caused by UV or apoptotic stress. Together, membrane WWOX/TβRII complex is needed for cell-to-cell recognition, maintaining the efficacy of Ca²⁺ influx, and control of cell invasiveness.

Recently defined epileptic encephalopathy related to WWOX gene mutation: six patients and new mutations

Purpose: Pathogenic variants of the WWOX gene have been linked to sexual differentiation disorders, spinocerebellar ataxia, and epileptic encephalopathy (EE). We evaluated the clinical and molecular data from six newly diagnosed patients with WWOX-related EE.Methods: Clinical and molecular findings in six patients with EE were investigated, and biallelic pathogenic variants in the WWOX gene were identified. Clinical exome sequencing and Sanger sequencing were performed.Results: Three variations, as well as two novel mutations, in the WWOX gene were detected.Conclusion: Pathogenic WWOX mutations are associated with early-onset EE. Here, we report the case of six children with WWOX-related EE.

Molecular Functions of WWOX Potentially Involved in Cancer Development

The WW domain-containing oxidoreductase gene (WWOX) was cloned 21 years ago as a putative tumor suppressor gene mapping to chromosomal fragile site FRA16D. The localization of WWOX in a chromosomal region frequently altered in human cancers has initiated multiple current studies to establish its role in this disease. All of this work suggests that WWOX, due to its ability to interact with a large number of partners, exerts its tumor suppressive activity through a wide variety of molecular actions that are mostly cell specific.

Neuronal deletion of Wwox, associated with WOREE syndrome, causes epilepsy and myelin defects

WOREE syndrome caused by human germline biallelic mutations in WWOX is a neurodevelopmental disorder characterized by intractable epilepsy, severe developmental delay, ataxia and premature death at the age of 2-4 years. The underlying mechanisms of WWOX actions are poorly understood. In the current study, we show that specific neuronal deletion of murine Wwox produces phenotypes typical of the Wwox-null mutation leading to brain hyperexcitability, intractable epilepsy, ataxia and postnatal lethality. A significant decrease in transcript levels of genes involved in myelination was observed in mouse cortex and hippocampus. Wwox-mutant mice exhibited reduced maturation of oligodendrocytes, reduced myelinated axons and impaired axonal conductivity. Brain hyperexcitability and hypomyelination were also revealed in human brain organoids with a WWOX deletion. These findings provide cellular and molecular evidence for myelination defects and hyperexcitability in the WOREE syndrome linked to neuronal function of WWOX.

Genetic Neonatal-Onset Epilepsies and Developmental/Epileptic Encephalopathies with Movement Disorders: A Systematic Review

Despite expanding next generation sequencing technologies and increasing clinical interest into complex neurologic phenotypes associating epilepsies and developmental/epileptic encephalopathies (DE/EE) with movement disorders (MD), these monogenic conditions have been less extensively investigated in the neonatal period compared to infancy. We reviewed the medical literature in the study period 2000–2020 to report on monogenic conditions characterized by neonatal onset epilepsy and/or DE/EE and development of an MD, and described their electroclinical, genetic and neuroimaging spectra. In accordance with a PRISMA statement, we created a data collection sheet and a protocol specifying inclusion and exclusion criteria. A total of 28 different genes (from 49 papers) leading to neonatal-onset DE/EE with multiple seizure types, mainly featuring tonic and myoclonic, but also focal motor seizures and a hyperkinetic MD in 89% of conditions, with neonatal onset in 22%, were identified. Neonatal seizure semiology, or MD age of onset, were not always available. The rate of hypokinetic MD was low, and was described from the neonatal period only, with WW domain containing oxidoreductase (WWOX) pathogenic variants. The outcome is characterized by high rates of associated neurodevelopmental disorders and microcephaly. Brain MRI findings are either normal or nonspecific in most conditions, but serial imaging can be necessary in order to detect progressive abnormalities. We found high genetic heterogeneity and low numbers of described patients. Neurological phenotypes are complex, reflecting the involvement of genes necessary for early brain development. Future studies should focus on accurate neonatal epileptic phenotyping, and detailed description of semiology and time-course, of the associated MD, especially for the rarest conditions.

Neurological Disorders Associated with WWOX Germline Mutations-A Comprehensive Overview

The transcriptional regulator WW domain-containing oxidoreductase (WWOX) is a key player in a number of cellular and biological processes including tumor suppression. Recent evidence has emerged associating WWOX with non-cancer disorders. Patients harboring pathogenic germline bi-allelic WWOX variants have been described with the rare devastating neurological syndromes autosomal recessive spinocerebellar ataxia 12 (SCAR12) (6 patients) and WWOX-related epileptic encephalopathy (DEE28 or WOREE syndrome) (56 patients). Individuals with these syndromes present with a highly heterogenous clinical spectrum, the most common clinical symptoms being severe epileptic encephalopathy and profound global developmental delay. Knowledge of the underlying pathophysiology of these syndromes, the range of variants of the WWOX gene and its genotype-phenotype correlations is limited, hampering therapeutic efforts. Therefore, there is a critical need to identify and consolidate all the reported variants in WWOX to distinguish between disease-causing alleles and their associated severity, and benign variants, with the aim of improving diagnosis and increasing therapeutic efforts. Here, we provide a comprehensive review of the literature on WWOX, and analyze the pathogenic variants from published and unpublished reports by collecting entries from the ClinVar, DECIPHER, VarSome, and PubMed databases to generate the largest dataset of WWOX pathogenic variants. We estimate the correlation between variant type and patient phenotype, and delineate the impact of each variant, and used GnomAD to cross reference these variants found in the general population. From these searches, we generated the largest published cohort of WWOX individuals. We conclude with a discussion on potential personalized medicine approaches to tackle the devastating disorders associated with WWOX mutations.

Rapid exome sequencing: revolutionises the management of acutely unwell neonates

Diagnosing acutely unwell infants with a potential genetic diagnosis can be challenging for healthcare professionals. Evidence suggests that up to 13% of critically unwell infants on the neonatal intensive care unit (NICU) have an underlying molecular diagnosis and when identified directly affects treatment decisions in 83%. On 1st October 2019, the National Health Service England (NHSE) launched a nationally commissioned service so that rapid whole-exome sequencing can be offered to critically unwell babies and children with a likely monogenic disorder who are admitted to NICU and paediatric intensive care unit (PICU). We present 7 cases from two neonatal units in the West Midlands (UK), where rapid exome sequencing has revealed a genetic diagnosis. Early genetic diagnosis in this cohort has influenced management in all (100%) cases, and in 57% (4 in 7 cases), it has helped in the decision to reorientate care. In some cases, early diagnosis has reduced the need for invasive and unnecessary investigations and avoided the need for post-mortem investigations. The genetic diagnosis has helped in counselling the families regarding the recurrence risk for future pregnancies. In some cases, this has provided parents with the reassurance of a low recurrence. In others, it has resulted in the offer of prenatal diagnosis or assisted conception technologies. What is Known: • Rapid whole-exome sequencing was commissioned in the UK in October 2019. • It is available for critically unwell babies with a likely monogenic aetiology. What is New: • It helps management planning for rare genetic disorders and future pregnancies counselling. • It can reduce the need for invasive investigations and overall intensive care costs.

WWOX Loss of Function in Neurodevelopmental and Neurodegenerative Disorders

The WWOX gene was initially discovered as a putative tumor suppressor. More recently, its association with multiple central nervous system (CNS) pathologies has been recognized. WWOX biallelic germline pathogenic variants have been implicated in spinocerebellar ataxia type 12 (SCAR12; MIM:614322) and in early infantile epileptic encephalopathy (EIEE28; MIM:616211). WWOX germline copy number variants have also been associated with autism spectrum disorder (ASD). All identified germline genomic variants lead to partial or complete loss of WWOX function. Importantly, large-scale genome-wide association studies have also identified WWOX as a risk gene for common neurodegenerative conditions such as Alzheimer's disease (AD) and multiple sclerosis (MS). Thus, the spectrum of CNS disorders associated with WWOX is broad and heterogeneous, and there is little understanding of potential mechanisms at play. Exploration of gene expression databases indicates that WWOX expression is comparatively higher in the human cerebellar cortex than in other CNS structures. However, RNA in-situ hybridization data from the Allen Mouse Brain Atlas show that specific regions of the basolateral amygdala (BLA), the medial entorhinal cortex (EC), and deep layers of the isocortex can be singled out as brain regions with specific higher levels of Wwox expression. These observations are in close agreement with single-cell RNA-seq data which indicate that neurons from the medial entorhinal cortex, Layer 5 from the frontal cortex as well as GABAergic basket cells and granule cells from cerebellar cortex are the specific neuronal subtypes that display the highest Wwox expression levels. Importantly, the brain regions and cell types in which WWOX is most abundantly expressed, such as the EC and BLA, are intimately linked to pathologies and syndromic conditions in turn associated with this gene, such as epilepsy, intellectual disability, ASD, and AD. Higher Wwox expression in interneurons and granule cells from cerebellum points to a direct link to the described cerebellar ataxia in cases of WWOX loss of function. We now know that total or partial impairment of WWOX function results in a wide and heterogeneous variety of neurodegenerative conditions for which the specific molecular mechanisms remain to be deciphered. Nevertheless, these observations indicate an important functional role for WWOX in normal development and function of the CNS. Evidence also indicates that disruption of WWOX expression at the gene or protein level in CNS has significant deleterious consequences.

Loss of Wwox Perturbs Neuronal Migration and Impairs Early Cortical Development

Mutations in the WWOX gene cause a broad range of ultra-rare neurodevelopmental and brain degenerative disorders, associated with a high likelihood of premature death in animal models as well as in humans. The encoded Wwox protein is a WW domain-containing oxidoreductase that participates in crucial biological processes including tumor suppression, cell growth/differentiation and regulation of steroid metabolism, while its role in neural development is less understood. We analyzed the exomes of a family affected with multiple pre- and postnatal anomalies, including cerebellar vermis hypoplasia, severe neurodevelopmental impairment and refractory epilepsy, and identified a segregating homozygous WWOX mutation leading to a premature stop codon. Abnormal cerebral cortex development due to a defective architecture of granular and molecular cell layers was found in the developing brain of a WWOX-deficient human fetus from this family. A similar disorganization of cortical layers was identified in lde/lde rats (carrying a homozygous truncating mutation which disrupts the active Wwox C-terminal domain) investigated at perinatal stages. Transcriptomic analyses of Wwox-depleted human neural progenitor cells showed an impaired expression of a number of neuronal migration-related genes encoding for tubulins, kinesins and associated proteins. These findings indicate that loss of Wwox may affect different cytoskeleton components and alter prenatal cortical development, highlighting a regulatory role of the WWOX gene in migrating neurons across different species.

The WWOX gene in brain development and pathology

Shortly after its discovery in 2000, WWOX was hailed as a tumor suppressor gene. In subsequent years of research, this function was confirmed indisputably. Majority of tumors show high rate of loss of heterozygosity and decreased expression of WWOX. Nevertheless, over the years, the range of its known functions, at the cellular, organ and system levels, has expanded to include metabolism and endocrine system control and CNS differentiation and functioning. Despite of its function as a tumor suppressor gene, WWOX genetic alternations were found in a number of metabolic and neural diseases. A lack of WWOX protein as a consequence of germline mutations results in brain development disturbances and malfunctions.

The Genetic Landscape of Epilepsy of Infancy with Migrating Focal Seizures

OBJECTIVE

Epilepsy of infancy with migrating focal seizures (EIMFS) is one of the most severe developmental and epileptic encephalopathies. We delineate the genetic causes and genotype-phenotype correlations of a large EIMFS cohort.

METHODS

Phenotypic and molecular data were analyzed on patients recruited through an international collaborative study.

RESULTS

We ascertained 135 patients from 128 unrelated families. Ninety-three of 135 (69%) had causative variants (42/55 previously reported) across 23 genes, including 9 novel EIMFS genes: de novo dominant GABRA1, GABRB1, ATP1A3; X-linked CDKL5, PIGA; and recessive ITPA, AIMP1, KARS, WWOX. The most frequently implicated genes were KCNT1 (36/135, 27%) and SCN2A (10/135, 7%). Mosaicism occurred in 2 probands (SCN2A, GABRB3) and 3 unaffected mothers (KCNT1). Median age at seizure onset was 4 weeks, with earlier onset in the SCN2A, KCNQ2, and BRAT1 groups. Epileptic spasms occurred in 22% patients. A total of 127 patients had severe to profound developmental impairment. All but 7 patients had ongoing seizures. Additional features included microcephaly, movement disorders, spasticity, and scoliosis. Mortality occurred in 33% at median age 2 years 7 months.

INTERPRETATION

We identified a genetic cause in 69% of patients with EIMFS. We highlight the genetic heterogeneity of EIMFS with 9 newly implicated genes, bringing the total number to 33. Mosaicism was observed in probands and parents, carrying critical implications for recurrence risk. EIMFS pathophysiology involves diverse molecular processes from gene and protein regulation to ion channel function and solute trafficking. ANN NEUROL 2019;86:821-831.

Early onset epileptic encephalopathy caused by novel compound heterozygous mutation of WWOX gene

The human WW domain containing oxidoreductase (WWOX) gene has been identified as a tumor suppressor gene. However, recent reports have demonstrated its dominant role in autosomal recessive disorders of the central nervous system, especially in early onset epileptic encephalopathy. Here, we report a Chinese case with novel compound heterozygous mutation of WWOX gene (c.229_230+2del mutation originated from her mother and c.1065dup (p.Ala356Serfs*173) variation from her father), and compare them to previously reported 59 WWOX-related epileptic encephalopathy (WOREE). Early onset and frequent epileptic seizures in the postnatal period, hypsarrhythmia patterns in EEG background and retarded development are the most important characteristics of WOREE in infants. Although the seizures in our case can be controlled by phenobarbital and topiramate, the prognosis of WOREE is poor.

Novel compound heterozygous mutations in the WWOX gene cause early infantile epileptic encephalopathy

Defects of WW domain-containing oxidoreductase (WWOX) has been associated with autosomal recessive spinocerebellar ataxia type 12 (SCAR12) and severe early-onset epileptic encephalopathy. The mutations in this gene can lead to global developmental delay, acquired microcephaly, and epilepsy. We report an infant with an autosomal recessive severe early-onset epileptic encephalopathy. Whole exome sequencing analysis was applied to the patient. Novel compound heterozygous mutations in the WWOX gene, c.173-2A > G and c.775 T > C (p.Ser259Pro), were identified. The present study expands our knowledge of WWOX mutations and related phenotypes, and provides new information on the genetic defects associated with this disease for clinical diagnosis.

The WWOX Gene Influences Cellular Pathways in the Neuronal Differentiation of Human Neural Progenitor Cells

The brain is the most functionally organized structure of all organs. It manages behavior, perception and higher cognitive functions. The WWOX gene is non-classical tumor suppressor gene, which has been shown to have an impact on proliferation, apoptosis and migration processes. Moreover, genetic aberrations in WWOX induce severe neuropathological phenotypes in humans and rodents. The aim of the present study was to investigate in detail the impact of WWOX on human neural progenitor cell (hNPC) maintenance and how depletion of WWOX disturbs signaling pathways playing a pivotal role in neuronal differentiation and central nervous system (CNS) organogenesis. hNPC with a silenced WWOX gene exhibited lowered mitochondrial redox potential, enhanced adhesion to fibronectin and extracellular matrix protein mixture, downregulation of MMP2/9 expression and impaired 3D growth. Global transcriptome analysis using cap analysis of gene expression (CAGE) found that WWOX downregulation significantly changes the expression of multiple genes engaged in cytoskeleton organization, adhesion, cell signaling and chromatin remodeling. The massive changes in gene expression caused by WWOX silencing may strongly affect the differentiation and migration of neurons in organogenesis, brain injury, cancerogenesis or neurodifferentiation. WWOX gene appears to be an important regulator of neural tissue architecture and function.

Loss of Wwox Causes Defective Development of Cerebral Cortex with Hypomyelination in a Rat Model of Lethal Dwarfism with Epilepsy

WW domain-containing oxidoreductase (Wwox) is a putative tumor suppressor. Several germline mutations of Wwox have been associated with infant neurological disorders characterized by epilepsy, growth retardation, and early death. Less is known, however, about the pathological link between Wwox mutations and these disorders or the physiological role of Wwox in brain development. In this study, we examined age-related expression and histological localization of Wwox in forebrains as well as the effects of loss of function mutations in the Wwox gene in the immature cortex of a rat model of lethal dwarfism with epilepsy (lde/lde). Immunostaining revealed that Wwox is expressed in neurons, astrocytes, and oligodendrocytes. lde/lde cortices were characterized by a reduction in neurite growth without a reduced number of neurons, severe reduction in myelination with a reduced number of mature oligodendrocytes, and a reduction in cell populations of astrocytes and microglia. These results indicate that Wwox is essential for normal development of neurons and glial cells in the cerebral cortex.