Severe CNS involvement in WWOX mutations: Description of five new cases

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.

Loss of fragile WWOX gene leads to senescence escape and genome instability

Induction of DNA damage response (DDR) to ensure accurate duplication of genetic information is crucial for maintaining genome integrity during DNA replication. Cellular senescence is a DDR mechanism that prevents the proliferation of cells with damaged DNA to avoid mitotic anomalies and inheritance of the damage over cell generations. Human WWOX gene resides within a common fragile site FRA16D that is preferentially prone to form breaks on metaphase chromosome upon replication stress. We report here that primary Wwox knockout (Wwox-/-) mouse embryonic fibroblasts (MEFs) and WWOX-knockdown human dermal fibroblasts failed to undergo replication-induced cellular senescence after multiple passages in vitro. Strikingly, by greater than 20 passages, accelerated cell cycle progression and increased apoptosis occurred in these late-passage Wwox-/- MEFs. These cells exhibited γH2AX upregulation and microsatellite instability, indicating massive accumulation of nuclear DNA lesions. Ultraviolet radiation-induced premature senescence was also blocked by WWOX knockdown in human HEK293T cells. Mechanistically, overproduction of cytosolic reactive oxygen species caused p16Ink4a promoter hypermethylation, aberrant p53/p21Cip1/Waf1 signaling axis and accelerated p27Kip1 protein degradation, thereby leading to the failure of senescence induction in Wwox-deficient cells after serial passage in culture. We determined that significantly reduced protein stability or loss-of-function A135P/V213G mutations in the DNA-binding domain of p53 caused defective induction of p21Cip1/Waf1 in late-passage Wwox-/- MEFs. Treatment of N-acetyl-L-cysteine prevented downregulation of cyclin-dependent kinase inhibitors and induced senescence in Wwox-/- MEFs. Our findings support an important role for fragile WWOX gene in inducing cellular senescence for maintaining genome integrity during DDR through alleviating oxidative stress.

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.

Antineoplastic Nature of WWOX in Glioblastoma Is Mainly a Consequence of Reduced Cell Viability and Invasion

Following the discovery of WWOX, research has moved in many directions, including the role of this putative tumor suppressor in the central nervous system and related diseases. The task of determining the nature of WWOX in glioblastoma (GBM) is still considered to be at the initial stage; however, the influence of this gene on the GBM malignant phenotype has already been reported. Because most of the available in vitro research does not consider several cellular GBM models or a wide range of investigated biological assays, the present study aimed to determine the main processes by which WWOX exhibits anticancer properties in GBM, while taking into account the phenotypic heterogeneity between cell lines. Ectopic WWOX overexpression was studied in T98G, DBTRG-05MG, U251MG, and U87MG cell lines that were compared with the use of assays investigating cell viability, proliferation, apoptosis, adhesion, clonogenicity, three-dimensional and anchorage-independent growth, and invasiveness. Observations presenting the antineoplastic properties of WWOX were consistent for T98G, U251MG, and U87MG. Increased proliferation and tumor growth were noted in WWOX-overexpressing DBTRG-05MG cells. A possible explanation for this, arrived at via bioinformatics tools, was linked to the TARDBP transcription factor and expression differences of USP25 and CPNE2 that regulate EGFR surface abundance. Collectively, and despite various cell line-specific circumstances, WWOX exhibits its anticancer nature mainly via a reduction of cell viability and invasiveness of glioblastoma.

WWOX inhibition by Zfra1-31 restores mitochondrial homeostasis and viability of neuronal cells exposed to high glucose

Diabetes has been associated with an increased risk of cognitive decline and dementia. However, the mechanisms underlying this association remain unclear and no effective therapeutic interventions exist. Accumulating evidence demonstrates that mitochondrial defects are a key feature of diabetes contributing to neurodegenerative events. It has also been demonstrated that the putative tumor suppressor WW domain-containing oxidoreductase 1 (WWOX) can interact with mitochondria in several pathological conditions. However, its role in diabetes-associated neurodegeneration remains unknown. So, this study aimed to evaluate the role of WWOX activation in high glucose-induced neuronal damage and death. Our experiments were mainly performed in differentiated SH-SY5Y neuroblastoma cells exposed to high glucose and treated (or not) with Zfra1-31, the specific inhibitor of WWOX. Several parameters were analyzed namely cell viability, WWOX activation (tyrosine 33 residue phosphorylation), mitochondrial function, reactive oxygen species (ROS) production, biogenesis, and dynamics, autophagy and oxidative stress/damage. The levels of the neurotoxic proteins amyloid β (Aβ) and phosphorylated Tau (pTau) and of synaptic integrity markers were also evaluated. We observed that high glucose increased the levels of activated WWOX. Interestingly, brain cortical and hippocampal homogenates from young (6-month old) diabetic GK rats showed increased levels of activated WWOX compared to older GK rats (12-month old) suggesting that WWOX plays an early role in the diabetic brain. In neuronal cells, high glucose impaired mitochondrial respiration, dynamics and biogenesis, increased mitochondrial ROS production and decreased mitochondrial membrane potential and ATP production. More, high glucose augmented oxidative stress/damage and the levels of Aβ and pTau proteins and affected autophagy, contributing to the loss of synaptic integrity and cell death. Of note, the activation of WWOX preceded mitochondrial dysfunction and cell death. Importantly, the inhibition of WWOX with Zfra1-31 reversed, totally or partially, the alterations promoted by high glucose. Altogether our observations demonstrate that under high glucose conditions WWOX activation contributes to mitochondrial anomalies and neuronal damage and death, which suggests that WWOX is a potential therapeutic target for early interventions. Our findings also support the efficacy of Zfra1-31 in treating hyperglycemia/diabetes-associated neurodegeneration.

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.

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.

Wwox Deficiency Causes Downregulation of Prosurvival ERK Signaling and Abnormal Homeostatic Responses in Mouse Skin

Deficiency of tumor suppressor WW domain-containing oxidoreductase (WWOX) in humans and animals leads to growth retardation and premature death during postnatal developmental stages. Skin integrity is essential for organism survival due to its protection against dehydration and hypothermia. Our previous report demonstrated that human epidermal suprabasal cells express WWOX protein, and the expression is gradually increased toward the superficial differentiated cells prior to cornification. Here, we investigated whether abnormal skin development and homeostasis occur under Wwox deficiency that may correlate with early death. We determined that keratinocyte proliferation and differentiation were decreased, while apoptosis was increased in Wwox^–/– mouse epidermis and primary keratinocyte cultures and WWOX-knockdown human HaCaT cells. Without WWOX, progenitor cells in hair follicle junctional zone underwent massive proliferation in early postnatal developmental stages and the stem/progenitor cell pools were depleted at postnatal day 21. These events lead to significantly decreased epidermal thickness, dehydration state, and delayed hair development in Wwox^–/– mouse skin, which is associated with downregulation of prosurvival MEK/ERK signaling in Wwox^–/– keratinocytes. Moreover, Wwox depletion results in substantial downregulation of dermal collagen contents in mice. Notably, Wwox^–/– mice exhibit severe loss of subcutaneous adipose tissue and significant hypothermia. Collectively, our knockout mouse model supports the validity of WWOX in assisting epidermal and adipose homeostasis, and the involvement of prosurvival ERK pathway in the homeostatic responses regulated by WWOX.

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.

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.

The expanding spectrum of movement disorders in genetic epilepsies

An ever-increasing number of neurogenetic conditions presenting with both epilepsy and atypical movements are now recognized. These disorders within the 'genetic epilepsy-dyskinesia' spectrum are clinically and genetically heterogeneous. Increased clinical awareness is therefore necessary for a rational diagnostic approach. Furthermore, careful interpretation of genetic results is key to establishing the correct diagnosis and initiating disease-specific management strategies in a timely fashion. In this review we describe the spectrum of movement disorders associated with genetically determined epilepsies. We also propose diagnostic strategies and putative pathogenic mechanisms causing these complex syndromes associated with both seizures and atypical motor control. WHAT THIS PAPER ADDS: Implicated genes encode proteins with very diverse functions. Pathophysiological mechanisms by which epilepsy and movement disorder phenotypes manifest are often not clear. Early diagnosis of treatable disorders is essential and next generation sequencing may be required.

Wwox deficiency leads to neurodevelopmental and degenerative neuropathies and glycogen synthase kinase 3β-mediated epileptic seizure activity in mice

Human WWOX gene resides in the chromosomal common fragile site FRA16D and encodes a tumor suppressor WW domain-containing oxidoreductase. Loss-of-function mutations in both alleles of WWOX gene lead to autosomal recessive abnormalities in pediatric patients from consanguineous families, including microcephaly, cerebellar ataxia with epilepsy, mental retardation, retinal degeneration, developmental delay and early death. Here, we report that targeted disruption of Wwox gene in mice causes neurodevelopmental disorders, encompassing abnormal neuronal differentiation and migration in the brain. Cerebral malformations, such as microcephaly and incomplete separation of the hemispheres by a partial interhemispheric fissure, neuronal disorganization and heterotopia, and defective cerebellar midline fusion are observed in Wwox^−/− mice. Degenerative alterations including severe hypomyelination in the central nervous system, optic nerve atrophy, Purkinje cell loss and granular cell apoptosis in the cerebellum, and peripheral nerve demyelination due to Schwann cell apoptosis correspond to reduced amplitudes and a latency prolongation of transcranial motor evoked potentials, motor deficits and gait ataxia in Wwox^−/− mice. Wwox gene ablation leads to the occurrence of spontaneous epilepsy and increased susceptibility to pilocarpine- and pentylenetetrazol (PTZ)-induced seizures in preweaning mice. We determined that a significantly increased activation of glycogen synthase kinase 3β (GSK3β) occurs in Wwox^−/− mouse cerebral cortex, hippocampus and cerebellum. Inhibition of GSK3β by lithium ion significantly abolishes the onset of PTZ-induced seizure in Wwox^−/− mice. Together, our findings reveal that the neurodevelopmental and neurodegenerative deficits in Wwox knockout mice strikingly recapitulate the key features of human neuropathies, and that targeting GSK3β with lithium ion ameliorates epilepsy.

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.

Novel WWOX deleterious variants cause early infantile epileptic encephalopathy, severe developmental delay and dysmorphism among Yemenite Jews

The human WW Domain Containing Oxidoreductase (WWOX) gene was originally described as a tumor suppressor gene. However, recent reports have demonstrated its cardinal role in the pathogenesis of central nervous systems disorders such as epileptic encephalopathy, intellectual disability, and spinocerebellar ataxia. We report on six patients from three unrelated families of full or partial Yemenite Jewish ancestry exhibiting early infantile epileptic encephalopathy and profound developmental delay. Importantly, four patients demonstrated facial dysmorphism. Exome sequencing revealed that four of the patients were homozygous for a novel WWOX c.517-2A > G splice-site variant and two were compound heterozygous for this variant and a novel c.689A > C, p.Gln230Pro missense variant. Complementary DNA sequencing demonstrated that the WWOX c.517-2A > G splice-site variant causes skipping of exon six. A carrier rate of 1:177 was found among Yemenite Jews. We provide the first detailed description of patients harboring a splice-site variant in the WWOX gene and propose that the clinical synopsis of WWOX related epileptic encephalopathy should be broadened to include facial dysmorphism. The increased frequency of the c.517-2A > G splice-site variant among Yemenite Jews coupled with the severity of the phenotype makes it a candidate for inclusion in expanded preconception screening programs.

The landscape of early infantile epileptic encephalopathy in a consanguineous population

PURPOSE

Epileptic encephalopathies (EE), are a group of age-related disorders characterized by intractable seizures and electroencephalogram (EEG) abnormalities that may result in cognitive and motor delay. Early infantile epileptic encephalopathies (EIEE) manifest in the first year of life. EIEE are highly heterogeneous genetically but a genetic etiology is only identified in half of the cases, typically in the form of de novo dominant mutations.

METHOD

This is a descriptive retrospective study of a consecutive series of patients diagnosed with EIEE from the participating hospitals. A chart review was performed for all patients. The diagnosis of epileptic encephalopathy was confirmed by molecular investigations in commercial labs. In silico study was done for all novel mutations. A systematic search was done for all the types of EIEE and their correlated genes in the literature using the Online Mendelian Inheritance In Man and PubMed databases.

RESULTS

In this case series, we report 72 molecularly characterized EIEE from a highly consanguineous population, and review their clinical course. We identified 50 variants, 26 of which are novel, causing 26 different types of EIEE. Unlike outbred populations, autosomal recessive EIEE accounted for half the cases. The phenotypes ranged from self-limiting and drug-responsive to severe refractory seizures or even death.

CONCLUSIONS

We reported the largest EIEE case series in the region with confirmed molecular testing and detailed clinical phenotyping. The number autosomal recessive predominance could be explained by the society's high consanguinity. We reviewed all the EIEE registered causative genes in the literature and proposed a functional classification.

Novel Homozygous Mutation in the WWOX Gene Causes Seizures and Global Developmental Delay: Report and Review

The WWOX gene has a WW domain containing oxidoreductase, which is located at the common fragile site FRA16D at chromosome 16q23. WWOX is a tumor suppressor gene that has been associated with several types of cancer such as hepatic, breast, lung, prostate, gastric, and ovarian. Recently WWOX has been implicated in epilepsy, where studies show homozygous loss-of-function mutation lead to early-infantile epileptic encephalopathy, spinocerebellar ataxia, intractable seizures and developmental delay, and early lethal microcephaly syndrome with epilepsy. Here we investigate two consanguineous Saudi families and we identified three probands with epileptic encephalopathy. Whole exome sequencing revealed a novel homozygous mutation in the WWOX gene in one proband. In addition, we identified a previously reported WWOX mutation in two probands. Later on these findings were confirmed with Sanger sequencing. The underlying mechanism on how WWOX mutations lead to seizure remains elusive. To date very few WWOX mutations have been associated with neurological disorder and our newly identified mutations support the notion that WWOX play an important role in neurons and will aid in better diagnosis and genetic counseling.

WWOX, the FRA16D gene: A target of and a contributor to genomic instability

WWOX is one of the largest human genes spanning over 1.11 Mbp in length at chr16q23.1-q23.2 and containing FRA16D, the second most common chromosomal fragile site. FRA16D is a hot spot of genomic instability, prone to breakage and for causing germline and somatic copy number variations (CNVs). Consequentially WWOX is frequent target for deletions in cancer. Esophageal, stomach, colon, bladder, ovarian, and uterine cancers are those most commonly affected by WWOX deep focal deletions. WWOX deletions significantly correlate with various clinicopathological features in esophageal carcinoma. WWOX is also a common target for translocations in multiple myeloma. By mapping R-loop (RNA:DNA hybrid) forming sequences (RFLS) we observe this to be a consistent feature aligning with germline and somatic CNV break points at the edges and core of FRA16D spanning from introns 5 to 8 of WWOX. Germline CNV polymorphisms affecting WWOX are extremely common in humans across different ethnic groups. Importantly, structural variants datasets allowed us to identify a specific hot spot for germline duplications and deletions within intron 5 of WWOX coinciding with the 5' edge of the FRA16D core and various RFLS. Recently, multiple pathogenic CNVs spanning WWOX have been identified associated with neurological conditions such as autism spectrum disorder, infantile epileptic encephalopathies, and other developmental anomalies. Loss of WWOX function has recently been associated with DNA damage repair abnormalities, increased genomic instability, and resistance to chemoradiotherapy. The described observations place WWOX both as a target of and a contributor to genomic instability. Both of these aspects will be discussed in this review.

Early infantile-onset epileptic encephalopathy 28 due to a homozygous microdeletion involving the WWOX gene in a region of uniparental disomy

The genetic etiologies of many rare disorders, including early infantile epileptic encephalopathies, are largely undiagnosed. A 6-year-old girl was admitted to the National Institutes of Health Undiagnosed Diseases Program with profound intellectual disability, infantile-onset seizures, chronic respiratory failure, facial dysmorphisms, skeletal abnormalities, and atrial septum defect. A large region of homozygosity was discovered on chromosome 16, spanning 16q22.1-16q24.3' caused by uniparental disomy (UPD) that included a maternally inherited homozygous microdeletion covering exon 6 of WWOX (NM_016373.3). mRNA expression analysis revealed that the deletion led to nonsense-mediated decay of the NM_016373.3 transcript; the exon 6 of an alternative transcript (NM_130791.3), lacking the short-chain dehydrogenase, was utilized. The microdeletion in WWOX explains the seizures and intellectual disability, while pathogenic variants in another gene, HSPG2, are likely responsible for the patient's skeletal abnormalities. This report describes a rare autosomal recessive disorder with multiple genetic etiologies, one of which involves UPD.

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

Purpose

Germline WWOX pathogenic variants have been associated with disorder of sex differentiation (DSD), spinocerebellar ataxia (SCA), and WWOX-related epileptic encephalopathy (WOREE syndrome). We review clinical and molecular data on WWOX-related disorders, further describing WOREE syndrome and phenotype/genotype correlations.

Methods

We report clinical and molecular findings in 20 additional patients from 18 unrelated families with WOREE syndrome and biallelic pathogenic variants in the WWOX gene. Different molecular screening approaches were used (quantitative polymerase chain reaction/multiplex ligation-dependent probe amplification [qPCR/MLPA], array comparative genomic hybridization [array-CGH], Sanger sequencing, epilepsy gene panel, exome sequencing), genome sequencing.

Results

Two copy-number variations (CNVs) or two single-nucleotide variations (SNVs) were found respectively in four and nine families, with compound heterozygosity for one SNV and one CNV in five families. Eight novel missense pathogenic variants have been described. By aggregating our patients with all cases reported in the literature, 37 patients from 27 families with WOREE syndrome are known. This review suggests WOREE syndrome is a very severe epileptic encephalopathy characterized by absence of language development and acquisition of walking, early-onset drug-resistant seizures, ophthalmological involvement, and a high likelihood of premature death. The most severe clinical presentation seems to be associated with null genotypes.

Conclusion

Germline pathogenic variants in WWOX are clearly associated with a severe early-onset epileptic encephalopathy. We report here the largest cohort of individuals with WOREE syndrome.

Modeling WWOX Loss of Function in vivo: What Have We Learned?

The WW domain–containing oxidoreductase (WWOX) gene encompasses a common fragile sites (CFS) known as FRA16D, and is implicated in cancer. WWOX encodes a 46kDa adaptor protein, which contains two N-terminal WW–domains and a catalytic domain at its C–terminus homologous to short–chain dehydrogenase/reductase (SDR) family proteins. A high sequence conservation of WWOX orthologues from insects to rodents and ultimately humans suggest its significant role in physiology and homeostasis. Indeed, data obtained from several animal models including flies, fish, and rodents demonstrate WWOX in vivo requirement and that its deregulation results in severe pathological consequences including growth retardation, post–natal lethality, neuropathy, metabolic disorders, and tumorigenesis. Altogether, these findings set WWOX as an essential protein that is necessary to maintain normal cellular/physiological homeostasis. Here, we review and discuss lessons and outcomes learned from modeling loss of WWOX expression in vivo.

Wwox deletion leads to reduced GABA-ergic inhibitory interneuron numbers and activation of microglia and astrocytes in mouse hippocampus

The association of WW domain-containing oxidoreductase WWOX gene loss of function with central nervous system (CNS) related pathologies is well documented. These include spinocerebellar ataxia, epilepsy and mental retardation (SCAR12, OMIM: 614322) and early infantile epileptic encephalopathy (EIEE28, OMIM: 616211) syndromes. However, there is complete lack of understanding of the pathophysiological mechanisms at play. In this study, using a Wwox knockout (Wwox KO) mouse model (2 weeks old, both sexes) and stereological studies we observe that Wwox deletion leads to a significant reduction in the number of hippocampal GABA-ergic (γ-aminobutyric acid) interneurons. Wwox KO mice displayed significantly reduced numbers of calcium-binding protein parvalbumin (PV) and neuropeptide Y (NPY) expressing interneurons in different subfields of the hippocampus in comparison to Wwox wild-type (WT) mice. We also detected decreased levels of Glutamic Acid Decarboxylase protein isoforms GAD65/67 expression in Wwox null hippocampi suggesting lower levels of GABA synthesis. In addition, Wwox deficiency was associated with signs of neuroinflammation such as evidence of activated microglia, astrogliosis, and overexpression of inflammatory cytokines Tnf-a and Il6. We also performed comparative transcriptome-wide expression analyses of neural stem cells grown as neurospheres from hippocampi of Wwox KO and WT mice thus identifying 283 genes significantly dysregulated in their expression. Functional annotation of transcriptome profiling differences identified 'neurological disease' and 'CNS development related functions' to be significantly enriched. Several epilepsy-related genes were found differentially expressed in Wwox KO neurospheres. This study provides the first genotype-phenotype observations as well as potential mechanistic clues associated with Wwox loss of function in the brain.

A novel missense variant in the SDR domain of the WWOX gene leads to complete loss of WWOX protein with early-onset epileptic encephalopathy and severe developmental delay

The human WWOX (WW domain-containing oxidoreductase) gene, originally known as a tumor suppressor gene, has been shown to be important for brain function and development. In recent years, mutations in WWOX have been associated with a wide phenotypic spectrum of autosomal recessively inherited neurodevelopmental disorders. Whole exome sequencing was completed followed by Sanger sequencing to verify segregation of the identified variants. Functional WWOX analysis was performed in fibroblasts of one patient. Transcription and translation were assessed by quantitative real-time PCR and Western blotting. We report two related patients who presented with early epilepsy refractory to treatment, progressive microcephaly, profound developmental delay, and brain MRI abnormalities. Additionally, one of the patients showed bilateral optic atrophy. Whole exome sequencing revealed homozygosity for a novel missense variant affecting the evolutionary conserved amino acid Gln230 in the catalytic short-chain dehydrogenase/reductase (SDR) domain of WWOX in both girls. Functional studies showed normal levels of WWOX transcripts but absence of WWOX protein. To our knowledge, our patients are the first individuals presenting the more severe end of the phenotypic spectrum of WWOX deficiency, although they were only affected by a single missense variant of WWOX. This could be explained by the functional data indicating an impaired translation or premature degradation of the WWOX protein.

Imaging structural and functional brain development in early childhood

In humans, the period from term birth to ∼2 years of age is characterized by rapid and dynamic brain development and plays an important role in cognitive development and risk of disorders such as autism and schizophrenia. Recent imaging studies have begun to delineate the growth trajectories of brain structure and function in the first years after birth and their relationship to cognition and risk of neuropsychiatric disorders. This Review discusses the development of grey and white matter and structural and functional networks, as well as genetic and environmental influences on early-childhood brain development. We also discuss initial evidence regarding the usefulness of early imaging biomarkers for predicting cognitive outcomes and risk of neuropsychiatric disorders.

Zfra restores memory deficits in Alzheimer's disease triple-transgenic mice by blocking aggregation of TRAPPC6AΔ, SH3GLB2, tau, and amyloid β, and inflammatory NF-κB activation

Introduction

Zinc finger-like protein that regulates apoptosis (Zfra) is a naturally occurring 31-amino-acid protein. Synthetic peptides Zfra1–31 and Zfra4–10 are known to effectively block the growth of many types of cancer cells.

Methods

Ten-month-old triple-transgenic (3×Tg) mice for Alzheimer's disease (AD) received synthetic Zfra peptides via tail vein injections, followed by examining restoration of memory deficits.

Results

Zfra significantly downregulated TRAPPC6AΔ, SH3GLB2, tau, and amyloid β (Αβ) aggregates in the brains of 3×Tg mice and effectively restored their memory capabilities. Zfra inhibited melanoma-induced neuronal death in the hippocampus and plaque formation in the cortex. Mechanistically, Zfra blocked the aggregation of amyloid β 42 and many serine-containing peptides in vitro, suppressed tumor necrosis factor–mediated NF-κB activation, and bound cytosolic proteins for accelerating their degradation in ubiquitin/proteasome-independent manner.

Discussion

Zfra peptides exhibit a strong efficacy in blocking tau aggregation and amyloid Αβ formation and restore memory deficits in 3×Tg mice, suggesting its potential for treatment of AD.

Novel mutations in WWOX, RARS2, and C10orf2 genes in consanguineous Arab families with intellectual disability

Intellectual disability is a heterogeneous disease with many genes and mutations influencing the phenotype. Consanguineous families constitute a rich resource for the identification of rare variants causing autosomal recessive disease, due to the effects of inbreeding. Here, we examine three consanguineous Arab families, recruited in a quest to identify novel genes/mutations. All the families had multiple offspring with non-specific intellectual disability. We identified homozygosity (autozygosity) intervals in those families through SNP genotyping and whole exome sequencing, with variants filtered using Ingenuity Variant Analysis (IVA) software. The families showed heterogeneity and novel mutations in three different genes known to be associated with intellectual disability. These mutations were not found in 514 ethnically matched control chromosomes. p.G410C in WWOX, p.H530Y in RARS2, and p.I69F in C10orf2 are novel changes that affect protein function and could give new insights into the development and function of the central nervous system.

Pleiotropic Functions of Tumor Suppressor WWOX in Normal and Cancer Cells

WW domain-containing oxidoreductase (WWOX), originally marked as a likely tumor suppressor gene, has over the years become recognized for its role in a much wider range of cellular activities. Phenotypic effects displayed in animal studies, along with resolution of WWOX's architecture, fold, and binding partners, point to the protein's multifaceted biological functions. Results from a series of complementary experiments seem to indicate WWOX's involvement in metabolic regulation. More recently, clinical studies involving cases of severe encephalopathy suggest that WWOX also plays a part in controlling CNS development, further expanding our understanding of the breadth and complexity of WWOX behavior. Here we present a short overview of the various approaches taken to study this dynamic gene, emphasizing the most recent findings regarding WWOX's metabolic- and CNS-associated functions and their underlying molecular basis.