Friday, July 17, 2020

WWOX epileptic encephalopathy

Inspired by a patient

Tarta-Arsene O, Barca D, Craiu D, Iliescu C. Practical clues for diagnosing WWOX encephalopathy. Epileptic Disord. 2017;19(3):357-361. doi:10.1684/epd.2017.0924

The WW domain-containing oxidoreductase gene is implicated in autosomal recessive disorders of the central nervous system, expressed either as spinocerebellar ataxia or as a severe form with early-infantile epileptic encephalopathy. Here, we describe the electroclinical evolution of these disorders, adding new diagnostic clues based on a case study. The patient, a boy with early-onset epilepsy, presented with profound global developmental delay, persistent hypsarrhythmia, and epileptic spasms, associated with progressive cerebral atrophy without microcephaly. Metabolic disease was excluded. Whole-exome sequencing showed mutations in the WW domain-containing oxidoreductase gene. Our findings extend the phenotypic traits of this aggressive epileptic encephalopathy, with persistent epileptic spasms and hypsarhythmia as a part of the electroclinical phenotype, demonstrating that microcephaly is not mandatory for diagnosis, even when associated with progressive cerebral atrophy. These mutations might be more frequent than expected among early-onset epileptic encephalopathies. We present practical clues for the diagnosis of WWOX encephalopathy in order to avoid unnecessary investigations and ensure appropriate genetic counselling for the families.

Iacomino M, Baldassari S, Tochigi Y, et al. Loss of Wwox Perturbs Neuronal Migration and Impairs Early Cortical Development. Front Neurosci. 2020;14:644. Published 2020 Jun 11. doi:10.3389/fnins.2020.00644

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.

Kośla K, Kałuzińska Ż, Bednarek AK. The WWOX gene in brain development and pathology [published online ahead of print, 2020 May 9]. Exp Biol Med (Maywood). 2020;1535370220924618. doi:10.1177/1535370220924618

WW domain-containing oxidoreductase encoded by the WWOX gene is a transcription regulator and a key player in a number of cellular and biological processes such as tumor suppression, cell proliferation, apoptosis induction, steroid metabolism, and central nervous system development. This review provides a comprehensive summary of currently known roles and discusses the importance of WWOX gene for CNS development and functioning.

Weisz-Hubshman M, Meirson H, Michaelson-Cohen R, et al. Novel WWOX deleterious variants cause early infantile epileptic encephalopathy, severe developmental delay and dysmorphism among Yemenite Jews. Eur J Paediatr Neurol. 2019;23(3):418-426. doi:10.1016/j.ejpn.2019.02.003

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.

Yang C, Zhang Y, Song Z, Yi Z, Li F. Novel compound heterozygous mutations in the WWOX gene cause early infantile epileptic encephalopathy. Int J Dev Neurosci. 2019;79:45-48. doi:10.1016/j.ijdevneu.2019.10.003

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.

Serin HM, Simsek E, Isik E, Gokben S. WWOX-associated encephalopathies: identification of the phenotypic spectrum and the resulting genotype-phenotype correlation. Neurol Sci. 2018;39(11):1977-1980. doi:10.1007/s10072-018-3528-6

Epileptic encephalopathies are a group of disorders in which epileptiform abnormalities cause progressive deterioration in cerebral function. Genetic causes have been described in several of the epileptic encephalopathies, and many previously unknown genes have been identified. WW domain-containing oxidoreductase (WWOX) has recently been implicated in autosomal recessive spinocerebellar ataxia type 12 (SCAR12) and severe early-onset epileptic encephalopathy. With whole-exome sequencing, we identified a homozygous WWOX missense mutation, p.Leu239Arg, in a girl from a consanguineous family with psychomotor developmental delay, acquired microcephaly, and epileptic seizures. WWOX-related epileptic encephalopathy is a rare condition but it should be considered in cases having early epileptic spasms and parental consanguinity.

1 comment:

  1. Piard J, Hawkes L, Milh M, et al. The phenotypic spectrum of WWOX-related disorders: 20 additional cases of WOREE syndrome and review of the literature [published correction appears in Genet Med. 2019 Feb 20;:]. Genet Med. 2019;21(6):1308-1318. doi:10.1038/s41436-018-0339-3

    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.