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Recurrent NEDD4L Variant in Periventricular Nodular Heterotopia, Polymicrogyria and Syndactyly.

ABSTRACT: NEDD4L encodes an ubiquitin ligase which is expressed in the cortex and ventricular zone of the fetal brain. Missense variants in NEDD4L have been reported in nine patients with periventricular nodular heterotopia (PNH), polymicrogyria, cleft palate, and syndactyly. All reported variants are located in the HECT domain, causing deregulation of signaling pathways, including the AKT/mTOR pathway. Here we describe a first familial case with four affected members with a high degree of intra-familial phenotypic variability. Phenotypic features in the proband consisted of severe neurodevelopmental delay, refractory seizures, bilateral PNH, and perisylvian polymicrogyria. The other family members were less severely affected with mild developmental delay and isolated bilateral PNH. All family members had syndactyly. An unrelated patient presented with severe neurodevelopmental delay, seizures, and hypospadias, expanding the phenotypic spectrum. MRI revealed bilateral PNH and perisylvian polymicrogyria. All tested patients carry the recurrent variant c.623G > A, p.(Arg208Gln) in the WW domain of NEDD4L. The variant in the unrelated patient occurred de novo. This is the first report of a NEDD4L variant located in the WW domain which is probably involved in the recognition of substrates for ligation suggesting a loss of function variant.

SUBMITTER: Stouffs K

PROVIDER: S-EPMC7013364 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Recurrent NEDD4L Variant in Periventricular Nodular Heterotopia, Polymicrogyria and Syndactyly.

Stouffs Katrien K Verloo Patrick P Brock Stefanie S Régal Luc L Beysen Diane D Ceulemans Berten B Jansen Anna C AC Meuwissen Marije E C MEC

Frontiers in genetics 20200205

NEDD4L encodes an ubiquitin ligase which is expressed in the cortex and ventricular zone of the fetal brain. Missense variants in NEDD4L have been reported in nine patients with periventricular nodular heterotopia (PNH), polymicrogyria, cleft palate, and syndactyly. All reported variants are located in the HECT domain, causing deregulation of signaling pathways, including the AKT/mTOR pathway. Here we describe a first familial case with four affected members with a high degree of intra-familial ...[more]

PMID: 32117442

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Project description:RationalePeriventricular nodular heterotopia-7 (PVNH7) is a neurodevelopmental disorder associated with improper neuronal migration during neurogenesis in cortex development caused by pathogenic variants in the NEDD4L gene.Patient concernsWe report the case of a polystigmatized 2-year-old boy having significant symptomatologic overlap with PVNH7, such as delayed psychomotor and mental development, seizures and infantile spasms, periventricular nodular heterotopia, polymicrogyria, cleft palate, 2 to 3 toe syndactyly, hypotonia, microretrognathia, strabismus, and absent speech and walking. The patient showed also distinct symptoms falling outside PVNH7 symptomatology, also present in the proband's older brother, such as blue sclerae, hydronephrosis, transversal palmar crease (found also in their father), and bilateral talipes equinovarus. In addition, the patient suffered from many other symptoms.DiagnosesThe boy, his brother and their parents were subjected to whole-exome sequencing. Because of uncertainties in symptomatology and inheritance pattern, the top-down approach was hard to apply. Using the bottom-up approach, we identified a known pathogenic variant, NM_001144967.2(NEDD4L):c.2677G>A:p.Glu893Lys, in the proband's genome that absented in any other analyzed family member, suggesting its de novo origin.Interventions and outcomesThe patient was treated with Convulex 300 mg/mL for the successful seizure control and Euthyrox 25mg for the treatment of thyroid malfunction. He also took various supplements for the metabolism support and digestion regulation. Moreover, the patient underwent the corrective surgeries of cleft palate and talipes equinovarus.LessonsWe successfully identified the causative mutation NM_001144967.2(NEDD4L):c.2677G>A:p.Glu893Lys explaining symptoms overlapping those reported for PVNH7. Symptoms shared with the brother were not explained by this variant, since he was not a carrier of the pathogenic NEDD4L variant. These are most likely not extended phenotypes of PVNH7, rather an independent clinical entity caused by a yet unidentified genetic factor in the family, highlighting thus the importance of thorough evaluation of symptomatology and genomic findings in affected and unaffected family members, when such data are available.

Project description:BackgroundNeurodevelopmental disorders associated with periventricular nodular heterotopia (PVNH) are characterized by phenotypic and genetic heterogeneity. NEDD4L mutation can lead to PVNH7. However, at present, only eight NEDD4L pathogenic variants have been identified across 15 cases of PVNH7 worldwide. Given this dearth of evidence, the precise correlations between genetic pathogenesis and phenotypes remain to be determined.MethodsThis report discusses the case of a 19-month-old male child with cleft palate, seizures, psychomotor retardation, and hypotonia, for whom we verified the genetic etiology using Trio-whole-exome and Sanger sequencing to analyze the potential pathogenicity of the mutant protein structure. Mutant plasmids were constructed for in vitro analyses. After transfection into human 293 T cells, the mutant transcription process was analyzed using real-time PCR (RT-PCR), and levels of mutant protein expression were examined using western blotting (WB) and immunofluorescence (IF) experiments.ResultsGenetic analyses revealed a novel missense mutation Gln900Arg, located in the homologous to E6-APC terminal (HECT) domain of NEDD4L and that the parents were wild-type, suggestive of a de novo mutation. The variant was predicted to be pathogenic by bioinformatics software, which also suggested alterations in the structural stability of the mutant protein. RT-PCR results indicated that the mutation did not affect mRNA expression, whereas WB and IF results indicated that the level of mutant protein was significantly reduced by 41.07%.ConclusionFunctional experiments demonstrated that Gln900Arg probably did not lead to transcriptional abnormalities in this patient, instead leading to increased ubiquitination activity owing to the constitutive activation of the HECT domain, thereby promoting protein degradation. Extensive clinical reports should be generated for patients presenting with PVNH and/or polymicrogyria, developmental delay, syndactyly, and hypotonia to increase the pool of evidence related to NEDD4L.

Project description:Heterozygous loss of function mutations within the Filamin A gene in Xq28 are the most frequent cause of bilateral neuronal periventricular nodular heterotopia (PVNH). Most affected females are reported to initially present with difficult to treat seizures at variable age of onset. Psychomotor development and cognition may be normal or mildly to moderately impaired. Distinct associated extracerebral findings have been observed and may help to establish the diagnosis including patent ductus arteriosus Botalli, progressive dystrophic cardiac valve disease and aortic dissection, chronic obstructive lung disease or chronic constipation. Genotype-phenotype correlations could not yet be established.Sanger sequencing and MLPA was performed for a large cohort of 47 patients with Filamin A associated PVNH (age range 1 to 65 years). For 34 patients more detailed clinical information was available from a structured questionnaire and medical charts on family history, development, epileptologic findings, neurological examination, cognition and associated clinical findings. Available detailed cerebral MR imaging was assessed for 20 patients.Thirty-nine different FLNA mutations were observed, they are mainly truncating (37/39) and distributed throughout the entire coding region. No obvious correlation between the number and extend of PVNH and the severity of the individual clinical manifestation was observed. 10 of the mutation carriers so far are without seizures at a median age of 19.7 years. 22 of 24 patients with available educational data were able to attend regular school and obtain professional education according to age.We report the clinical and mutation spectrum as well as MR imaging for a large cohort of 47 patients with Filamin A associated PVNH including two adult males. Our data are reassuring in regard to psychomotor and cognitive development, which is within normal range for the majority of patients. However, a concerning median diagnostic latency of 17 to 20 years was noted between seizure onset and the genetic diagnosis, intensely delaying appropriate medical surveillance for potentially life threatening cardiovascular complications as well as genetic risk assessment and counseling prior to family planning for this X-linked dominant inherited disorder with high perinatal lethality in hemizygous males.

Project description:BACKGROUND: X-linked periventricular nodular heterotopia is a disorder of neuronal migration resulting from mutations in the filamin A gene. This is an X-linked dominant condition where most affected patients are female and present with seizures. Extra-cerebral features such as cardiac abnormalities and thrombocytopenia have also been documented. Loss of function mutations in filamin A are predicted to result in prenatal lethality in males. Somatic mosaicism and mutations that lead to partial loss of function of the protein are hypothesized to explain viability of males reported in the literature. We report the first case of germline mosaicism involving a loss of function mutation in filamin A in a family where brain MRI, clinical exam, and mutation analysis is normal in both biological parents. CASE PRESENTATION: The index patient, a 39 year old female with normal development, had her first seizure at 24 years with no evidence of any precipitating factors. Brain MRI shows bilateral periventricular nodular heterotopia. She has thrombocytopenia and an echocardiogram at age 32 years revealed a mildly dilated aortic root and ascending aorta with mild aortic regurgitation. The second patient, the 36 year old younger sister of the index case, is currently healthy with no evidence of seizures or cardiac abnormalities. Her brain MRI is consistent with bilateral periventricular nodular heterotopia. The mother is healthy at 57 years of age with a normal brain MRI. The father is healthy at 59 years of age with a normal brain MRI. DNA sequencing of lymphocyte extracted DNA from the two sisters shows a c.2002C?>?T transition in exon 13 of filamin A resulting in a p.Gln668Ter mutation. This nonsense mutation was not detected in peripheral blood lymphocytes from the unaffected parents. CONCLUSION: This report provides evidence for germline mosaicism in filamin A-associated periventricular nodular heterotopia. This case must now be considered when providing genetic counseling to families where a proband presents as an isolated case and parental investigations are unremarkable.

Dataset Information

Recurrent NEDD4L Variant in Periventricular Nodular Heterotopia, Polymicrogyria and Syndactyly.

Publications

Recurrent NEDD4L Variant in Periventricular Nodular Heterotopia, Polymicrogyria and Syndactyly.

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