ZFHX3 variants cause childhood partial epilepsy and infantile spasms with favourable outcomes.

BACKGROUND: The ZFHX3 gene plays vital roles in embryonic development, cell proliferation, neuronal differentiation and neuronal death. This study aims to explore the relationship between ZFHX3 variants and epilepsy. METHODS: Whole-exome sequencing was performed in a cohort of 378 patients with partial (focal) epilepsy. A Drosophila Zfh2 knockdown model was used to validate the association between ZFHX3 and epilepsy. RESULTS: Compound heterozygous ZFHX3 variants were identified in eight unrelated cases. The burden of ZFHX3 variants was significantly higher in the case cohort, shown by multiple/specific statistical analyses. In Zfh2 knockdown flies, the incidence and duration of seizure-like behaviour were significantly greater than those in the controls. The Zfh2 knockdown flies exhibited more firing in excitatory neurons. All patients presented partial seizures. The five patients with variants in the C-terminus/N-terminus presented mild partial epilepsy. The other three patients included one who experienced frequent non-convulsive status epilepticus and two who had early spasms. These three patients had also neurodevelopmental abnormalities and were diagnosed as developmental epileptic encephalopathy (DEE), but achieved seizure-free after antiepileptic-drug treatment without adrenocorticotropic-hormone/steroids. The analyses of temporal expression (genetic dependent stages) indicated that ZFHX3 orthologous were highly expressed in the embryonic stage and decreased dramatically after birth. CONCLUSION: ZFHX3 is a novel causative gene of childhood partial epilepsy and DEE. The patients of infantile spasms achieved seizure-free after treatment without adrenocorticotropic-hormone/steroids implies a significance of genetic diagnosis in precise treatment. The genetic dependent stage provided an insight into the underlying mechanism of the evolutional course of illness.

Clinical and functional consequences of GRIA variants in patients with neurological diseases.

AMPA receptors are members of the glutamate receptor family and mediate a fast component of excitatory synaptic transmission at virtually all central synapses. Thus, their functional characteristics are a critical determinant of brain function. We evaluate intolerance of each GRIA gene to genetic variation using 3DMTR and report here the functional consequences of 52 missense variants in GRIA1-4 identified in patients with various neurological disorders. These variants produce changes in agonist EC50, response time course, desensitization, and/or receptor surface expression. We predict that these functional and localization changes will have important consequences for circuit function, and therefore likely contribute to the patients' clinical phenotype. We evaluated the sensitivity of variant receptors to AMPAR-selective modulators including FDA-approved drugs to explore potential targeted therapeutic options.

Both epilepsy and anti-seizure medications affect bone metabolism in children with self-limited epilepsy with centrotemporal spikes.

OBJECTIVE: Bone metabolism can be influenced by a range of factors. We selected children with self-limited epilepsy with centrotemporal spikes (SeLECTS) and lifestyles similar to those of healthy children to control for the confounding factors that may influence bone metabolism. We aimed to identify the specific effects of epilepsy and/or anti-seizure medications (ASMs) on bone metabolism. METHODS: Patients with SeLECTS were divided into an untreated group and a monotherapy group, and the third group was a healthy control group. We determined the levels of various biochemical markers of bone metabolism, including procollagen type I nitrogenous propeptide (PINP), alkaline phosphatase (ALP), osteocalcin (OC), collagen type I cross-linked C-telopeptide (CTX), calcium, magnesium, phosphorus, parathyroid hormone (PTH), and vitamin D3 (VD3 ). RESULTS: A total of 1487 patients (from 19 centers) were diagnosed with SeLECTS; 1032 were analyzed, including 117 patients who did not receive any ASMs (untreated group), 643 patients who received only one ASM (monotherapy group), and 272 children in the healthy control group. Except for VD3 , other bone metabolism of the three groups were different (p < .001). Bone metabolism was significantly lower in the untreated group than the healthy control group (p < .05). There were significant differences between the monotherapy and healthy control group in the level of many markers. However, when comparing the monotherapy and untreated groups, the results were different; oxcarbazepine, levetiracetam, and topiramate had no significant effect on bone metabolism. Phosphorus and magnesium were significantly lower in the valproic acid group than the untreated group (adjusted p < .05, Cliff's delta .282-.768). CTX was significantly higher in the lamotrigine group than in the untreated group (adjusted p = .012, Cliff's delta = .316). SIGNIFICANCE: Epilepsy can affect many aspects of bone metabolism. After controlling epilepsy and other confounders that affect bone metabolism, we found that the effects of ASMs on bone metabolism differed. Oxcarbazepine, levetiracetam, and topiramate did not affect bone metabolism, and lamotrigine corrected some of the abnormal markers of bone metabolism in patients with epilepsy.

Efficacy and safety of switching from brand-name to domestic generic levetiracetam in children with epilepsy. / å·¦ä¹™æ‹‰è¥¿å¦çš„å›½äº§ä»¿åˆ¶è¯æ›¿æ¢æ²»ç–—å„¿ç«¥ç™«ç—«çš„ç–—æ•ˆåŠå®‰å ¨æ€§ç ”ç©¶.

OBJECTIVES: To study the efficacy and safety of domestic generic levetiracetam in replacement of brand-name levetiracetam in the treatment of children with epilepsy. METHODS: A retrospective analysis was performed on the medical data of 154 children with epilepsy who received domestic generic levetiracetam in the inpatient or outpatient service of Guangdong Provincial People's Hospital from May 2019 to December 2020. Domestic generic levetiracetam and brand-name levetiracetam were compared in terms of efficacy and safety. RESULTS: For these 154 children, the epilepsy control rate was 77.3% (119/154) at baseline. At 6 months after switching to domestic generic levetiracetam, the epilepsy control rate reached 83.8% (129/154), which showed a significant increase (P<0.05). There was no significant change in the frequency of seizures from baseline to 6 months after switching (P>0.05). The incidence of refractory epilepsy in children with no response after switching treatment was significantly higher than that in children with response (P<0.05). Before switching, only 1 child (0.6%) experienced somnolence, while after switching, 3 children (1.9%) experienced mild adverse drug reactions, including dizziness, somnolence, irritability, and bad temper. CONCLUSIONS: Switching from brand-name to generic levetiracetam is safe and effective and holds promise for clinical application, but more prospective randomized controlled trials are required in future.

[Effect of Ilepcimide Combined Western Drugs on Serum Level of Neuron Specific Enolase in Treating Epilepsy Children Patients].

Objective To observe changes of serum neuron specific enolase (NSE) level in children patients with epilepsy by additional use of ilepcimide (piperine derivative). Methods Totally 107 epilepsy children patients were assigned to the test group (77 cases) and the control group (30 cases) ac- cording to random digit table. Children patients in the control group received anti-epileptic Western drugs only. Those in the test group additionally took ilepcimide, 5 mg/kg per day as initial dose, taken in two times. The dose was gradually added to those without control of epilepsy attack. Added dose within a week should not exceed 10 mg/kg per day. The therapeutic course for all was one year. Electoencephalo- gram (EEG) was performed before treatment, half a year after treatment, and one year after treatment, respectively. Serum NSE level was detected using electrochemiluminescence. Efficacy was assessed after 1-year treatment. Results The total effective rate was 65. 0% (50177) in the test group, with statistical difference as compared with that in the control group [30. 0% (9/30), P <0. 01 ]. Compared with before treatment, serum NES-level obviously decreased in the test group after 0. 5-year treatment and 1- year treatment respectively (P <0. 05, P <0. 01). Besides, serum NES level was lower after 1-year treatment than after 0. 5-year treatment (P <0. 05, P <0. 01). There was no statistical difference in serum NES level between the test group and the control group at each time point (P >0. 05). Results of EEG were obviously superior in the test group (3 with normal range EEG, 5 critically abnormal EEG, 69 abnormal EEG) to the control group (2 with normal range EEG and 75 abnormal EEG) after 1-year treatment, with statistical difference (Z= -2. 33, P <0. 05). There was no statistical difference in EEG results of the control group between before treatment (all abnormal EEG) and after 1-year treatment (3 critically abnormal EEG and 27 abnormal EEG) (Z = -1. 732, P > 0. 05). Conclusion Adding ilepcimide (piperine derivative) for epilepsy children patients could lower serum NSE level and the frequency of seizures, and improve results of EEG.

[Clinical analysis of 15 pediatric patients with tuberous sclerosis complex complicated by cardiac rhabdomyomas].

OBJECTIVE: To investigate the clinical features in children with tuberous sclerosis complex (TSC)-associated cardiac rhabdomyomas (CRM). METHODS: The clinical data of 15 children with TSC complicated by CRM were collected. The clinical features of the patients were analyzed, and TSC gene mutations were detected. RESULTS: Eleven cases (73%) developed multiple CRM. The majority of the tumors were located in the left and right ventricles. Most tumors presented as a round-like hyperechogenic mass with a clear margin on echocardiography. Arrhythmias occurred in 3 patients and 2 patients experienced heart failure. Gene mutation tests were performed in 2 patients, and pathogenic mutations were detected in both patients, which were TSC1 mutation and TSC2 mutation, respectively. Three patients were followed up for 6 to 38 months, and their CRM shrank or regressed spontaneously. CONCLUSIONS: TSC-associated CRM is generally multiple. Heart failure and arrhythmias may occur in some patients. Echocardiography is important for diagnosis of CRM. TSC-associated CRM has an inclination to spontaneous regression. TSC can be diagnosed at a molecular genetic level by TSC gene mutation detection.

Correlation between interictal cerebral glucose hypometabolism and IQ in children with epilepsy.

The aim of this study was to understand the relationship between IQ and glucose metabolism in brain cells in a wide variety of subjects with epilepsy. The study participants were 78 children with epilepsy and 15 healthy children for comparison. All participants were administered the Chinese Wechsler Intelligence Scale for Children (C-WISC). The verbal intelligence quotient (VIQ), performance intelligence quotient (PIQ), and full-scale intelligence quotient (FIQ) were compared between children with epilepsy and typically developing children. Seventy-eight patients underwent interictal positron emission computed tomography (PET) using 2-deoxy-2[(18)F]fluoro-d-glucose (FDG) as the tracer for evaluating brain glucose metabolism. Verbal intelligence quotient, PIQ, and FIQ based on the C-WISC were significantly lower in children with epilepsy than those in the healthy comparison group (P<0.001, P=0.001, and P<0.001, respectively). The IQ of patients with normal metabolism, unifocal abnormal hypometabolism, and multifocal abnormal hypometabolism determined by PET differed significantly. The extent of the abnormal hypometabolism was negatively correlated with the FIQ (rs=-0.549, P<0.001). In patients with lateralized hypometabolism based on PET, the VIQ/PIQ discrepancy scores (|VIQ-PIQ|≥15 points) differed significantly between the left hemisphere abnormal hypometabolism and right hemisphere abnormal hypometabolism subgroups, with negative values in the left and positive values in the right subgroups (P=0.004). In conclusion, brain metabolic abnormalities are correlated with IQ, and performing interictal PET along with C-WISC can better assess the extent of severity of cognitive impairment and VIQ/PIQ discrepancy.

CABP4 mutation in mice shows alteration in protein expression level and neuron discharge frequency.

Background: The calcium-binding protein 4 (CABP4) gene is a newly identified epilepsy-related gene that might be associated with a rare type of genetic focal epilepsy; that is, autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). In vitro, mutant CABP4 causes an increased inward flow voltage of calcium ions and a significant increase in the electrical signal discharge in hippocampus neurons; however, the role of CABP4 in epilepsy has not yet been specifically described, and there is not yet a CABP4 mutant animal model recapitulating the epilepsy phenotype. Methods: We introduced a human CABP4 missense mutation into the C57BL/6J mouse genome and generated a knock-in strain carrying a glycine-to-aspartic acid mutation in the gene. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot were performed to evaluate the CABP4 expression level. Slice patch-clamp recording was carried out on pyramidal cells of prefrontal cortex layers II and III. Results: The CABP4G155D/+ mutant mice were viable and born at an expected Mendelian ratio. Surprisingly, the heterozygous (HE) mice did not display either an abnormal appearance or an overt seizure phenotype, and there was no statistically significant difference between the HE and wild-type (WT) mice in terms of overall messenger RNA (mRNA) and protein expression. However, the HE mutant mice showed an imbalance in the amount of protein expressed in the brain regions. Additionally, the patch-clamp recordings from the HE mouse layer II/III cortical pyramidal cells revealed an increase in the frequency of micro-excitatory post-synaptic currents (mEPSCs) but no change in the amplitude was observed. Conclusions: The findings of this study suggest that the CABP4 p.G155D mutation might be one of the mechanisms underlying seizure onset.

DYNC1H1 variants associated with infant-onset epilepsy without neurodevelopmental disorders.

OBJECTIVES: The DYNC1H1 variants are associated with abnormal brain morphology and neuromuscular disorders that are accompanied by epilepsy. This study aimed to explore the relationship between DYNC1H1 variants and epilepsy. MATERIALS AND METHODS: Trios-based whole-exome sequencing was performed on patients with epilepsy. Previously reported epilepsy-related DYNC1H1 variants were systematically reviewed to analyse genotype-phenotype correlation. RESULTS: The DYNC1H1 variants were identified in four unrelated cases of infant-onset epilepsy, including two de novo and two biallelic variants. Two patients harbouring de novo missense variants located in the stem and stalk domains presented with refractory epilepsies, whereas two patients harbouring biallelic variants located in the regions between functional domains had mild epilepsy with infrequent focal seizures and favourable outcomes. One patient presented with pachygyria and neurodevelopmental abnormalities, and the other three patients presented with normal development. These variants have no or low frequencies in the Genome Aggregation Database. All the missense variants were predicted to be damaging using silico tools. Previously reported epilepsy-related variants were monoallelic variants, mainly de novo missense variants, and all the patients presented with severe epileptic phenotypes or developmental delay and malformations of cortical development. Epilepsy-related variants were clustered in the dimerization and stalk domains, and generalized epilepsy-associated variants were distributed in the stem domain. CONCLUSION: This study suggested that DYNC1H1 variants are potentially associated with infant-onset epilepsy without neurodevelopmental disorders, expanding the phenotypic spectrum of DYNC1H1. The genotype-phenotype correlation helps to understand the underlying mechanisms of phenotypic variation.

MED12 variants associated with X-linked recessive partial epilepsy without intellectual disability.

OBJECTIVES: The MED12 gene encodes mediator complex subunit 12, which is a component of the mediator complex involved in the transcriptional regulation of nearly all RNA polymerase II-dependent genes. MED12 variants have previously been associated with developmental disorders with or without nonspecific intellectual disability. This study aims to explore the association between MED12 variants and epilepsy. MATERIALS AND METHODS: Trios-based whole-exome sequencing was performed in a cohort of 349 unrelated cases with partial (focal) epilepsy without acquired causes. The genotype-phenotype correlations of MED12 variants were analyzed. RESULTS: Five hemizygous missense MED12 variants, including c.958A>G/p.Ile320Val, c.1757G>A/p.Ser586Asn, c.2138C>T/p.Pro713Leu, c.3379T>C/p.Ser1127Pro, and c.4219A>C/p.Met1407Leu were identified in five unrelated males with partial epilepsy. All patients showed infrequent focal seizures and achieved seizure free without developmental abnormalities or intellectual disability. All the hemizygous variants were inherited from asymptomatic mothers (consistent with the X-linked recessive inheritance pattern) and were absent in the general population. The two variants with damaging hydrogen bonds were associated with early-onset seizures. Further genotype-phenotype analysis revealed that congenital anomaly disorder (Hardikar syndrome) was associated with (de novo) destructive variants in an X-linked dominant inheritance pattern, whereas epilepsy was associated with missense variants in an X-linked recessive inheritance pattern. Phenotypic features of intellectual disability appeared as the intermediate phenotype in terms of both genotype and inheritance. Epilepsy-related variants were located at the MED12-LCEWAV domain and the regions between MED12-LCEWAV and MED12-POL. CONCLUSION: MED12 is a potentially causative gene for X-linked recessive partial epilepsy without developmental or intellectual abnormalities. The genotype-phenotype correlation of MED12 variants explains the phenotypic variations and can help the genetic diagnosis.

Corrigendum: ATP6V0C is associated with febrile seizures and epilepsy with febrile seizures plus.

[This corrects the article DOI: 10.3389/fnmol.2022.889534.].

Reprint of: Recessive APC2 missense variants associated with epilepsies without neurodevelopmental disorders.

OBJECTIVES: The APC2 gene, encoding adenomatous polyposis coli protein-2, is involved in cytoskeletal regulation in neurons responding to endogenous extracellular signals and plays an important role in brain development. Previously, the APC2 variants have been reported to be associated with cortical dysplasia and intellectual disability. This study aims to explore the association between APC2 variants and epilepsy. METHODS: Whole-exome sequencing (WES) was performed in cases (trios) with epilepsies of unknown causes. The damaging effects of variants were predicted by protein modeling and in silico tools. Previously reported APC2 variants were reviewed to analyze the genotype-phenotype correlations. RESULTS: Four pairs of compound heterozygous missense variants were identified in four unrelated patients with epilepsy without brain malformation/intellectual disability. All variants presented no or low allele frequencies in the controls. The missense variants were predicted to be damaging by silico tools, and affect hydrogen bonding with surrounding amino acids or decreased protein stability. Patients with variants that resulted in significant changes in protein stability exhibited more severe and intractable epilepsy, whereas patients with variants that had minor effect on protein stability exhibited relatively mild phenotypes. The previously reported APC2 variants in patients with complex cortical dysplasia with other brain malformations-10 (CDCBM10; MIM: 618677) were all truncating variants; in contrast, the variants identified in epilepsy in this study were all missense variants, suggesting a potential genotype-phenotype correlation. SIGNIFICANCE: This study suggests that APC2 is potentially associated with epilepsy without brain malformation/intellectual disability. The genotype-phenotype correlation helps to understand the underlying mechanisms of phenotypic heterogeneity.

Expanding the genetic and phenotypic relevance of CLCN4 variants in neurodevelopmental condition: 13 new patients.

OBJECTIVES: CLCN4 variations have recently been identified as a genetic cause of X-linked neurodevelopmental disorders. This study aims to broaden the phenotypic spectrum of CLCN4-related condition and correlate it with functional consequences of CLCN4 variants. METHODS: We described 13 individuals with CLCN4-related neurodevelopmental disorder. We analyzed the functional consequence of the unreported variants using heterologous expression, biochemistry, confocal fluorescent microscopy, patch-clamp electrophysiology, and minigene splicing assay. RESULTS: We identified five novel (p.R41W, p.L348V, p.G480R, p.R603W, c.1576 + 5G > A) and three known (p.T203I, p.V275M, p.A555V) pathogenic CLCN4 variants in 13 Chinese patients. The p.V275M variant is found at high frequency and seen in four unrelated individuals. All had global developmental delay (GDD)/intellectual disability (ID). Seizures were present in eight individuals, and 62.5% of them developed refractory epilepsy. Five individuals without seizures showed moderate to severe GDD/ID. Developmental delay precedes seizure onset in most patients. The variants p.R41W, p.L348V, and p.R603W compromise the anion/exchange function of ClC-4. p.R41W partially impairs ClC-3/ClC-4 association. p.G480R reduces ClC-4 expression levels and impairs the heterodimerization with ClC-3. The c.1576 + 5G > A variant causes 22 bp deletion of exon 10. CONCLUSIONS: We further define and broaden the clinical and mutational spectrum of CLCN4-related neurodevelopmental conditions. The p.V275M variant may be a potential hotspot CLCN4 variant in Chinese patients. The five novel variants cause loss of function of ClC-4. Transport dysfunction, protein instability, intracellular trafficking defect, or failure of ClC-4 to oligomerize may contribute to the pathophysiological events leading to CLCN4-related neurodevelopmental disorder.

[Clinical features and mutation analysis of CHRNA4 gene for families and sporadic cases affected with autosomal dominant nocturnal frontal lobe epilepsy].

OBJECTIVE: To investigate mutations of CHRNA4 gene in Chinese patients with autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). METHODS: Two hundred and fifty-seven patients (including 215 sporadic and 42 familial cases) were analyzed. Mutational screening was performed by sequencing all of the 6 exons of the CHRNA4 gene including the donor and acceptor splice sites. RESULTS: The results have excluded the involvement of any known mutations of the CHRNA4 gene. A novel synonymous mutation c.570C>T(D190D) and 6 single nucleotide polymorphisms (SNPs) of the CHRNA4 gene were detected in 6 sporadic cases, including c.639T/C, c.678T/C, c.1209G/T, c.1227T/C, c.1659G/A, and c.1629C/T. The SNP D190D was hererozygous and absent in 200 healthy controls. CONCLUSION: This results suggested that mutations of the CHRNA4 gene may be rare in southern Chinese population with ADNFLE. The synonymous mutation D190D has not been reported previously. Its impact on the pathogenesis of ADNFLE warrant further study.

Recessive APC2 missense variants associated with epilepsies without neurodevelopmental disorders.

OBJECTIVES: The APC2 gene, encoding adenomatous polyposis coli protein-2, is involved in cytoskeletal regulation in neurons responding to endogenous extracellular signals and plays an important role in brain development. Previously, the APC2 variants have been reported to be associated with cortical dysplasia and intellectual disability. This study aims to explore the association between APC2 variants and epilepsy. METHODS: Whole-exome sequencing (WES) was performed in cases (trios) with epilepsies of unknown causes. The damaging effects of variants were predicted by protein modeling and in silico tools. Previously reported APC2 variants were reviewed to analyze the genotype-phenotype correlations. RESULTS: Four pairs of compound heterozygous missense variants were identified in four unrelated patients with epilepsy without brain malformation/intellectual disability. All variants presented no or low allele frequencies in the controls. The missense variants were predicted to be damaging by silico tools, and affect hydrogen bonding with surrounding amino acids or decreased protein stability. Patients with variants that resulted in significant changes in protein stability exhibited more severe and intractable epilepsy, whereas patients with variants that had minor effect on protein stability exhibited relatively mild phenotypes. The previously reported APC2 variants in patients with complex cortical dysplasia with other brain malformations-10 (CDCBM10; MIM: 618677) were all truncating variants; in contrast, the variants identified in epilepsy in this study were all missense variants, suggesting a potential genotype-phenotype correlation. SIGNIFICANCE: This study suggests that APC2 is potentially associated with epilepsy without brain malformation/intellectual disability. The genotype-phenotype correlation helps to understand the underlying mechanisms of phenotypic heterogeneity.

DLG3 variants caused X-linked epilepsy with/without neurodevelopmental disorders and the genotype-phenotype correlation.

Background: The DLG3 gene encodes disks large membrane-associated guanylate kinase scaffold protein 3, which plays essential roles in the clustering of N-methyl-D-aspartate receptors (NMDARs) at excitatory synapses. Previously, DLG3 has been identified as the causative gene of X-linked intellectual developmental disorder-90 (XLID-90; OMIM# 300850). This study aims to explore the phenotypic spectrum of DLG3 and the genotype-phenotype correlation. Methods: Trios-based whole-exome sequencing was performed in patients with epilepsy of unknown causes. To analyze the genotype-phenotype correlations, previously reported DLG3 variants were systematically reviewed. Results: DLG3 variants were identified in seven unrelated cases with epilepsy. These variants had no hemizygous frequencies in controls. All variants were predicted to be damaging by silico tools and alter the hydrogen bonds with surrounding residues and/or protein stability. Four cases mainly presented with generalized seizures, including generalized tonic-clonic and myoclonic seizures, and the other three cases exhibited secondary generalized tonic-clonic seizures and focal seizures. Multifocal discharges were recorded in all cases during electroencephalography monitoring, including the four cases with generalized discharges initially but multifocal discharges after drug treating. Protein-protein interaction network analysis revealed that DLG3 interacts with 52 genes with high confidence, in which the majority of disease-causing genes were associated with a wide spectrum of neurodevelopmental disorder (NDD) and epilepsy. Three patients with variants locating outside functional domains all achieved seizure-free, while the four patients with variants locating in functional domains presented poor control of seizures. Analysis of previously reported cases revealed that patients with non-null variants presented higher percentages of epilepsy than those with null variants, suggesting a genotype-phenotype correlation. Significance: This study suggested that DLG3 variants were associated with epilepsy with/without NDD, expanding the phenotypic spectrum of DLG3. The observed genotype-phenotype correlation potentially contributes to the understanding of the underlying mechanisms driving phenotypic variation.

HCFC1 variants in the proteolysis domain are associated with X-linked idiopathic partial epilepsy: Exploring the underlying mechanism.

BACKGROUND: HCFC1 encodes transcriptional co-regulator HCF-1, which undergoes an unusual proteolytic maturation at a centrally located proteolysis domain. HCFC1 variants were associated with X-linked cobalamin metabolism disorders and mental retardation-3. This study aimed to explore the role of HCFC1 variants in common epilepsy and the mechanism underlying phenotype heterogeneity. METHODS: Whole-exome sequencing was performed in a cohort of 313 patients with idiopathic partial (focal) epilepsy. Functional studies determined the effects of the variants on the proteolytic maturation of HCF-1, cell proliferation and MMACHC expression. The role of HCFC1 variants in partial epilepsy was validated in another cohort from multiple centers. RESULTS: We identified seven hemizygous HCFC1 variants in 11 cases and confirmed the finding in the validation cohort with additional 13 cases and six more hemizygous variants. All patients showed partial epilepsies with favorable outcome. None of them had cobalamin disorders. Functional studies demonstrated that the variants in the proteolysis domain impaired the maturation by disrupting the cleavage process with loss of inhibition of cell growth but did not affect MMACHC expression that was associated with cobalamin disorder. The degree of functional impairment was correlated with the severity of phenotype. Further analysis demonstrated that variants within the proteolysis domain were associated with common and mild partial epilepsy, whereas those in the kelch domain were associated with cobalamin disorder featured by severe and even fatal epileptic encephalopathy, and those in the basic and acidic domains were associated with mainly intellectual disability. CONCLUSION: HCFC1 is potentially a candidate gene for common partial epilepsy with distinct underlying mechanism of proteolysis dysfunction. The HCF-1 domains played distinct functional roles and were associated with different clinical phenotypes, suggesting a sub-molecular effect. The distinct difference between cobalamin disorders and idiopathic partial epilepsy in phenotype and pathogenic mechanism, implied a clinical significance in early diagnosis and management.

A novel missense creatine mutant of CaBP4, c.464G>A (p.G155D), associated with autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE), reduces the expression of CaBP4.

Background: CaBP4 encodes Ca2+-binding protein 4, a neuronal Ca2+-binding protein that participates in many cellular processes by regulating the concentration of free Ca2+ ions. De novo CaBP4 variants have been identified as a cause of congenital stationary night blindness (CSNB). However, we recently reported a 4-generation pedigree with 11 individuals diagnosed with autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) that were validated with only one novel missense mutation, c.464G>A (p.G155D), in CaBP4. De novo CaBP4 variants have never been reported to be related with ADNFLE. This study aimed to identify whether c.464G>A (p.G155D) in CaBP4 reduced the expression of CaBP4. Methods: In vitro experiments using recombinant protein expressed in human neuron cells were utilized in this study. Real-time polymerase chain reaction (RT-PCR) was performed to evaluate the effect of c.464G>A on CaBP4 mRNA expression. Western blot was performed to assess the effect of c.464G>A on CaBP4 protein expression. Results: According to the RT-PCR and Western blot results, c.464G>A (p.G155D) was associated with an increased expression of CaBP4 mRNA and a reduced expression of CaBP4 protein. Conclusions: These results reveal that c.464G>A (p.G155D) in CaBP4 reduced the expression of CaBP4 by reducing the stability of the CaBP4 protein. Mutations in the CaBP4 gene may be associated with ADNFLE.

Functional characterization of a KCNAB3 genetic epilepsy with febrile seizures plus adult mouse model.

Background: Genetic epilepsy with febrile seizures plus (GEFS+) is a type of epileptic syndrome closely related to heredity factors, which can be caused by gene mutations. However, it still remains unclear how these mutations result in seizures. Previously, we identified a new heterozygous missense mutation of the KCNAB3 gene, H258R, in the GEFS+ family; the electric currents of the human embryonic kidney 293 (HEK293) cells co-expressing Kvß3 (H258R) and Kv1.1 showed obvious inactivation. This study sought to examine the effects of this mutation on the potassium channels in the mammalian brain. Methods: Mutant mice were generated by introducing the human H258R missense mutation within exon 10 at an equivalent position in the mouse KCNAB3 gene via CRISPR/Cas9 and homologous recombination. A patch clamp was used to detect the potassium currents in the pyramidal cells of the hippocampal CA1 region of the mutant mice. The total potassium currents of the pyramidal cells in the hippocampal CA1 region of KCNAB3 [wild-type (WT)] and KCNAB3 (H258R) adult mice were recorded with increased voltage. Results: We found a decreased total potassium current in the H258R group but no significant differences at a maximum voltage (+80 mV; P>0.05). Conclusions: These results suggest that the KCNAB3 mutation reduced hippocampal potassium currents in this mouse model.

BCOR variants are associated with X-linked recessive partial epilepsy.

OBJECTIVE: BCOR gene, encoding a corepressor of BCL6, plays an important role in fetal development. BCOR mutations were previously associated with oculofaciocardiodental syndrome (OFCD or MCOPS2, OMIM# 300166). The BCOR protein is ubiquitously expressed in multiple areas, including the brain. However, the role of BCOR in neurological disorder remains elusive. METHODS: Trios-based whole-exome sequencing was performed in a cohort of 323 cases with partial epilepsy without acquired causes. RESULTS: Seven hemizygous missense BCOR variants, including c 0.103 G>C/p.Asp35His, c.1079 A>G/p.His360Arg, c 0.1097 C>T/p.Thr366Ile, c 0.3301 C>T/p.Pro1101Ser, c 0.3391 C>T/p.Arg1131Trp, c 0.4199 G>A/p.Arg1400Gln, and c 0.5254 G>A/p.Asp1752Asn, were identified in seven cases with partial epilepsy. Two patients presented partial seizures with generalized seizures and/or generalized discharges. One case showed cortical dysplasia in the right temporal-occipital area on MRI. Two cases presented mild developmental delay. However, all patients achieved seizure-free. The frequency of BCOR variants in the present cohort was significantly higher than that in the controls of healthy Chinese volunteers and all populations of Genome Aggregation Database (gnomAD). Computational modeling, including hydrogen bond and prediction of protein stability, implied that the variants lead to structural impairment. Previously, OFCD associated BCOR mutations were mostly destructive mutations in an X-linked dominant (XLD) pattern; in contrast, the BCOR variants identified in this study were all missense variants, which were associated with partial epilepsy in an X-linked recessive (XLR) pattern. The proportion of missense mutations in epilepsy was significantly higher than that in OFCD. CONCLUSIONS: BCOR was potentially a candidate pathogenic gene of partial epilepsy with or without developmental delay. The genotype-phenotype correlation helps understanding the mechanism underlying phenotypic variation.