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Two novel PCDH19 mutations in Russian patients with epilepsy with intellectual disability limited to females: a case report.

ABSTRACT: BACKGROUND:Epilepsy with intellectual disability limited to females (Epileptic encephalopathy, early infantile, 9; EIEE9) is a rare early infantile epileptic encephalopathy characterized by an unusual X-linked inheritance: females with heterozygous mutations are affected, while hemizygous males are not. CASE PRESENTATION:We describe the clinical and molecular characteristics of 2 Russian patients with EIEE9 (females, ages 3?years and 7?years). In these patients seizures developed at the age of 3?years. Additionally, for our patients and for cases described in the literature we searched for a possible relationship between the type and localization of the mutation and the EIEE9 clinical phenotype. CONCLUSIONS:We identified two novel PCDH19 mutations in EIEE9 patients: a missense mutation in exon 1 (c.1236C?>?A, p.Asp412Glu) and a frameshift in exon 3 (c.2386_2387insGTCT, p.Thr796fs). We conclude that the age of seizure onset and the presence of intellectual disability may depend not on the type and localization of PCDH19 mutations, but on the X-inactivation status. The study also highlights the need to screen for EIEE9 among young female epilepsy patients.

SUBMITTER: Kozina AA

PROVIDER: S-EPMC7579871 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Two novel PCDH19 mutations in Russian patients with epilepsy with intellectual disability limited to females: a case report.

Kozina Anastasiya Aleksandrovna AA Okuneva Elena Grigorievna EG Baryshnikova Natalia Vladimirovna NV Fedonyuk Inessa Dmitrievna ID Kholin Alexey Aleksandrovich AA Il'ina Elena Stepanovna ES Krasnenko Anna Yurievna AY Stetsenko Ivan Fedorovich IF Plotnikov Nikolay Alekseevich NA Klimchuk Olesia Igorevna OI Surkova Ekaterina Ivanovna EI Ilinsky Valery Vladimirovich VV

BMC medical genetics 20201021 1

<h4>Background</h4>Epilepsy with intellectual disability limited to females (Epileptic encephalopathy, early infantile, 9; EIEE9) is a rare early infantile epileptic encephalopathy characterized by an unusual X-linked inheritance: females with heterozygous mutations are affected, while hemizygous males are not.<h4>Case presentation</h4>We describe the clinical and molecular characteristics of 2 Russian patients with EIEE9 (females, ages 3 years and 7 years). In these patients seizures developed ...[more]

PMID: 33087045

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Project description:RATIONALE:Epilepsy with mental retardation limited to females (EFMR) is a rare type of X-linked epilepsy disorder, affecting heterozygous females disproportionately. The pathogenesis of EFMR has been identified as mutations in the protocadherin 19 (PCDH19) gene. To data, more than 60 different mutations in PCDH19 have been identified. Most of them are located at exon 1, but we describe a novel deletion mutation c.2468delT at exon 3 of PCDH19. PATIENT CONCERNS:The patient was an 11-year-old girl with onset of seizures at the age of 18 months and followed by progressive intellectual disability (ID) later. DIAGNOSIS:The girl was diagnosed as EFMR when a novel deletion mutation c.2468delT at exon 3 of PCDH19 was found. The deletion mutation c.2468delT was predicted to have caused a frameshift mutation of amino acid at position 823 (p.L823fs). There was no family history of seizures or ID. Her father was asymptomatic, but the mutation screening shows that he had a hemizygous mutation c.2468delT at the same site of PCDH19. The secondary structure of PCDH19 (wide type) showed that the sequences undergoing frameshift mutations were located in the cytoplasm and contain 9 phosphorylation sites. The p.L823fs mutation caused a totally different amino sequence after position of 823, thereby resulting in the disappearance of phosphorylation sites. The frameshift mutation of amino acid at position 823 might affect its binding capability with GABAA receptor and results in migration and morphological maturation of hippocampal neurons. INTERVENTIONS:The patient has received antiepileptic treatments, including sodium valproate, carbamazepine, levetiracetam, topiramate and clonazepam et al. OUTCOMES:: The antiepileptic treatment effects were limited. LESSONS:This case report describes a novel PCDH19 gene mutation (c.2468delT) at exon 3 in a girl suffering from EFMR. The deletion mutation was predicted to cause a frameshift mutation-p.L823fs, which is highly conserved across different species.

Project description:We identified six novel de novo human KCNQ5 variants in children with motor/language delay, intellectual disability (ID), and/or epilepsy by whole exome sequencing. These variants, comprising two nonsense and four missense alterations, were functionally characterized by electrophysiology in HEK293/CHO cells, together with four previously reported KCNQ5 missense variants (Lehman A, Thouta S, Mancini GM, Naidu S, van Slegtenhorst M, McWalter K, Person R, Mwenifumbo J, Salvarinova R; CAUSES Study; EPGEN Study; Guella I, McKenzie MB, Datta A, Connolly MB, Kalkhoran SM, Poburko D, Friedman JM, Farrer MJ, Demos M, Desai S, Claydon T. Am J Hum Genet 101: 65-74, 2017). Surprisingly, all eight missense variants resulted in gain of function (GOF) due to hyperpolarized voltage dependence of activation or slowed deactivation kinetics, whereas the two nonsense variants were confirmed to be loss of function (LOF). One severe GOF allele (P369T) was tested and found to extend a dominant GOF effect to heteromeric KCNQ5/3 channels. Clinical presentations were associated with altered KCNQ5 channel gating: milder presentations with LOF or smaller GOF shifts in voltage dependence [change in voltage at half-maximal conduction (ΔV50) = ∼-15 mV] and severe presentations with larger GOF shifts in voltage dependence (ΔV50 = ∼-30 mV). To examine LOF pathogenicity, two Kcnq5 LOF mouse lines were created with CRISPR/Cas9. Both lines exhibited handling- and thermal-induced seizures and abnormal cortical EEGs consistent with epileptiform activity. Our study thus provides evidence for in vivo KCNQ5 LOF pathogenicity and strengthens the contribution of both LOF and GOF mutations to global pediatric neurological impairment, including ID/epilepsy.NEW & NOTEWORTHY Six novel de novo human KCNQ5 variants were identified from children with neurodevelopmental delay, intellectual disability, and/or epilepsy. Expression of these variants along with four previously reported KCNQ5 variants from a similar cohort revealed GOF potassium channels, negatively shifted in V50 of activation and/or delayed deactivation kinetics. GOF is extended to KCNQ5/3 heteromeric channels, making these the predominant channels affected in heterozygous de novo patients. Kcnq5 LOF mice exhibited seizures, consistent with in vivo pathogenicity.

Project description:UNLABELLED: BACKGROUND: Array comparative genomic hybridization (CGH) has been repeatedly shown to be a successful tool for the identification of genomic variations in a clinical population. During the last decade, the implementation of array CGH has resulted in the identification of new causative submicroscopic chromosome imbalances and copy number variations (CNVs) in neuropsychiatric (neurobehavioral) diseases. Currently, array-CGH-based technologies have become an integral part of molecular diagnosis and research in individuals with neuropsychiatric disorders and children with intellectual disability (mental retardation) and congenital anomalies. Here, we introduce the Russian cohort of children with intellectual disability, autism, epilepsy and congenital anomalies analyzed by BAC array CGH and a novel bioinformatic strategy. RESULTS: Among 54 individuals highly selected according to clinical criteria and molecular and cytogenetic data (from 2426 patients evaluated cytogenetically and molecularly between November 2007 and May 2012), chromosomal imbalances were detected in 26 individuals (48%). In two patients (4%), a previously undescribed condition was observed. The latter has been designated as meiotic (constitutional) genomic instability resulted in multiple submicroscopic rearrangements (including CNVs). Using bioinformatic strategy, we were able to identify clinically relevant CNVs in 15 individuals (28%). Selected cases were confirmed by molecular cytogenetic and molecular genetic methods. Eight out of 26 chromosomal imbalances (31%) have not been previously reported. Among them, three cases were co-occurrence of subtle chromosome 9 and 21 deletions. CONCLUSIONS: We conducted an array CGH study of Russian patients suffering from intellectual disability, autism, epilepsy and congenital anomalies. In total, phenotypic manifestations of clinically relevant genomic variations were found to result from genomic rearrangements affecting 1247 disease-causing and pathway-involved genes. Obviously, a significantly lesser part of them are true candidates for intellectual disability, autism or epilepsy. The success of our preliminary array CGH and bioinformatic study allows us to expand the cohort. According to the available literature, this is the first comprehensive array CGH evaluation of a Russian cohort of children with neuropsychiatric disorders and congenital anomalies.

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Two novel PCDH19 mutations in Russian patients with epilepsy with intellectual disability limited to females: a case report.

Publications

Two novel PCDH19 mutations in Russian patients with epilepsy with intellectual disability limited to females: a case report.

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