Genotype and phenotype analysis of epilepsy caused by ADGRV1 mutations in Chinese children.

OBJECTIVE: To investigate the genotype and phenotype of epilepsy caused by ADGRV1 variants in Chinese children. METHODS: A total of 625 patients with epilepsy who had undergone whole-exon gene sequencing or epilepsy and related paroxysmal disease gene panel sequencing were recruited. Variants were evaluated for susceptibility pathogenicity based on their frequency in the Genome Aggregation Database (≤ 0.001). We used six algorithms (sorting intolerant from tolerant (SIFT), PolyPhen-2, Mutation Taster, CADD, REVEL and Splice AI) that predicted that the ADGRV1 variant would have a harmful impact on the function of genes and gene products. We retrospectively reviewed the clinical information of patients with susceptible pathogenic ADGRV1 variants. The relationship between the genotype and phenotype was also analyzed. RESULTS: Eighteen patients with epilepsy were found to have likely pathogenic variants in ADGRV1. The rate of ADGRV1 variants in patients with epilepsy in this cohort was 2.88%. A total of 19 ADGRV1 variants were found, of which 13 were novel and 6 had been previously reported. Eleven out of the 18 children (61.1%) had febrile and afebrile seizures (FS and AS), two children had only FS, one child had infantile spasms, and the other four children had only AS that occurred during sleep (Rolandic epilepsy or atypical Rolandic epilepsy). SIGNIFICANCE: Our study showed a statistically significant association between ADGRV1 variants and FS and AS (p < 0.05), supporting the hypothesis that ADGRV1 is a susceptibility gene for Rolandic epilepsy and infantile spasms. Most epilepsy cases caused by ADGRV1 variants have a good prognosis.

The Correlation of ELP4-PAX6 With Rolandic Spike Sources in Idiopathic Rolandic Epilepsy Syndromes.

Objective: To study the single nucleotide polymorphism rs662702 of ELP4-PAX6 in patients with idiopathic rolandic epilepsy syndromes (IRES) in China and explore the relationship between the distribution of rolandic spike sources and the single nucleotide polymorphism rs662702 in ELP4-PAX6. Methods: First, clinical information was obtained from patients diagnosed with IRES. Next, the single nucleotide polymorphism rs662702 of ELP4 was analyzed by using the Sanger method. Resting-state magnetoencephalography data were collected from 17 patients. We analyzed the epileptic spike sources using the single equivalent current dipole (SECD) model and determined the spike distributions across the whole brain. Finally, Fisher's test was performed to assess the correlation between the single nucleotide polymorphism rs662702 of ELP4-PAX6 and rolandic spike sources. Results: ELP4 rs662702 T alleles were found in 10.7% of IRES patients and occurred four times more frequently in these patients than in the healthy controls. TT homozygosity was found in one IRES patient (1.3%), while no TT homozygosity was found in the healthy control group. The IRES rolandic spike sources were unilateral in sixteen patients (94.1%) and were mainly located in the anterior central gyrus (58.8%). The spike source of patients without the ELP4 rs662702 T allele was correlated with the central region (p < 0.05). The rolandic spikes sources were significant correlated with the non-central gyrus (frontal and temporal lobes) in patients with the ELP4 rs662702 T allele (p < 0.05). Conclusion: The rolandic spike sources of the IRES patients with the ELP4 rs662702 T allele were significantly associated with the non-central gyrus, including the frontal and temporal lobes. Our study confirmed for the first time in vivo that ELP4 rs662702 T allele overexpression is correlated with the rolandic spike distribution in patients with IRES and provides important insights into how genetic abnormalities can lead to brain dysfunction and into the precise targeting of abnormal discharge sources in the brain.

Frequency-specific changes in the default mode network in patients with cingulate gyrus epilepsy.

To identify abnormal functional connectivity of the default mode network in cingulate gyrus epilepsy, which may yield new information about the default mode network and suggest a new cingulate gyrus epilepsy biomarker. Fifteen patients with cingulate gyrus epilepsy (mean age = 21 years) and 15 healthy controls (mean age = 24 years) were studied in the resting state using magnetoencephalography. Twelve brain areas of interest in the default mode network were extracted and investigated with multifrequency signals that included alpha (α, 8-13 Hz), beta (ß, 14-30 Hz), and gamma (γ, 31-80 Hz) band oscillations. Patients with cingulate gyrus epilepsy had significantly greater connectivity in all three frequency bands (α, ß, γ). A frequency-specific elevation of functional connectivity was found in patients compared to controls. The greater functional connectivity in the γ band was significantly more prominent than that of the α and ß bands. Patients with cingulate gyrus epilepsy and controls differed significantly in functional connectivity between the left angular gyrus and left posterior cingulate cortex in the α, ß, and γ bands. The results of the node degree analysis were similar to those of the functional connectivity analysis. Our findings reveal for the first time that brain activity in the γ band may play a key role in the default mode network in cingulate gyrus epilepsy. Altered functional connectivity of the left angular gyrus and left posterior cingulate cortex may be a new biomarker for cingulate gyrus epilepsy.

Gain-of-function mutation p.Arg225Cys in SCN11A causes familial episodic pain and contributes to essential tremor.

Familial episodic pain is a rare autosomal-dominant disorder characterized by recurrent attacks of pain. The pathogenesis of familial episodic pain is not very clear so far. Essential tremor is the most common movement disorder, but the identification of essential tremor genes has remained elusive. We studied a four-generation Chinese family with early-onset familial episodic pain and adult onset familial essential tremor. All essential tremor diagnoses were confirmed based on a review of the questionnaires, videotaped neurological examinations and was then reconfirmed by a senior neurologist specializing in movement disorders using published criteria. SCN11A analysis was performed by whole-exome sequencing or Sanger sequencing. We confirmed the presence of the SCN11A (c.673C>T) mutation in family members with episodic pain and essential tremor. We identified a missense mutation of p.Arg225Cys in SCN11A in a four-generation Chinese family with early-onset familial episodic pain and adult onset familial essential tremor syndrome. This may belong to a rare hereditary syndrome that has not been reported up to now. For the first time, we associated the genetic variability of SCN11A with the development of essential tremor, and further confirmed essential tremor is one of the neurological channelopathies.

Endoplasmic reticulum stress intolerance in EIF2B3 mutant oligodendrocytes is modulated by depressed autophagy.

OBJECTIVE: Eukaryotic translation initiation factor 2B (eIF2B) is an essential factor for the initiation of protein synthesis. Mutations in eIF2B encoded by EIF2B1-5 cause a lethal leukoencephalopathy--vanishing white matter disease (VWM). Previous studies have suggested that an improper activated unfolded protein response (UPR) after endoplasmic reticulum stress (ERS) contributed to the pathogenesis of the disease. Autophagy, an important compensatory pathway after ERS, was analyzed in this study. METHODS: To determine the tolerance differences to ERS, cell viability and apoptosis rates were detected in oligodendrocyte cell lines transfected with EIF2B3-c.1037T>C or the wild type. Autophagy flux was measured between groups. Autophagy inducers and inhibitors were used to identify the role of autophagy in the mutant oligodendrocytes. RESULTS: We confirmed that oligodendrocytes with mutant EIF2B3 was less tolerant to ERS than the wild type, with decreased cell viability and increased apoptosis rates. Autophagy flux was depressed in mutant oligodendrocytes under baseline condition and after ERS stimulation. Reduced expression of autophagy related gene (Atg) 3 and Atg 7 were involved in the depression of autophagy flux. The mutant oligodendrocytes pretreated with autophagy inducers showed stable cell viability and decreased apoptosis despite ERS induction, whereas the autophagy inhibitors aggravated cell apoptosis and viability declination. CONCLUSIONS: Oligodendrocytes transfected with mutant EIF2B3 was less tolerant to ERS than the wild type. Depressed autophagy flux was observed in the mutant cells at baseline and after ERS stimulation. Improperly depressed autophagy played a role in the susceptibility to ERS in EIF2B3 mutant oligodendrocytes.

Fifteen novel EIF2B1-5 mutations identified in Chinese children with leukoencephalopathy with vanishing white matter and a long term follow-up.

Leukoencephalopathy with vanishing white matter (VWM) is one of the most prevalent inherited childhood white matter disorders, which caused by mutations in each of the five subunits of eukaryotic translation initiation factor 2B (EIF2B1-5). In our study, 34 out of the 36 clinically diagnosed children (94%) were identified to have EIF2B1-5 mutations by sequencing. 15 novel mutations were identified. CNVs were not detected in patients with only one mutant allele and mutation-negative determined by gene sequencing. There is a significantly higher incidence of patients with EIF2B3 mutations compared with Caucasian patients (32% vs. 4%). c.1037T>C (p.Ile346Thr) in EIF2B3 was confirmed to be a founder mutation in Chinese, which probably one of the causes of the genotypic differences between ethnicities. Our average 4.4 years-follow-up on infantile, early childhood and juvenile VWM children suggested a rapid deterioration in motor function. Episodic aggravation was presented in 90% of infantile cases and 71.4% of childhood cases. 10 patients died during the follow-up. The Kaplan-Meier curve showed that the median survival time is 8.83 ± 1.51 years. This is the largest sample of children in a VWM follow-up study, which is helpful for a more depth understanding about the natural course.

Functional analysis of recently identified mutations in eukaryotic translation initiation factor 2Bɛ (eIF2Bɛ) identified in Chinese patients with vanishing white matter disease.

Vanishing white matter disease (VWM) is the first human hereditary disease known to be caused by defects in initiation of protein synthesis. Gene defects in each of the five subunits of eukaryotic translation initiation factor 2B (eIF2B α-ɛ) are responsible for the disease, although the mechanism of the pathogenesis is not well understood. In our previous study, four novel eIF2Bɛ mutations were found in Chinese patients: p.Asp62Val, p.Cys335Ser, p.Asn376Asp and p.Ser610-Asp613del. Functional analysis was performed on these mutations and the recently reported p.Arg269X. Our data showed that all resulted in a decrease in the guanine nucleotide exchange (GEF) activity of the eIF2B complex. p.Arg269X and p.Ser610-Asp613del mutants displayed the lowest activity, followed by p.Cys335Ser, p.Asn376Asp and p.Asp62Val. p.Arg269X and p.Ser610-Asp613del could not produce stable eIF2Bɛ, leading to almost complete loss-of-function. No evidence was obtained for the three missense mutations in changes in eIF2Bɛ protein level or eIF2BɛSer(540) phosphorylation, and disruption of holocomplex assembly, or binding to eIF2. All patients in our study had the classical phenotype. p.Asp62Val and p.Asn376Asp mutations caused only mildly decreased GEF activity, were probably responsible for relatively mild phenotype in cases of classical VWM.

Identification of novel EIF2B mutations in Chinese patients with vanishing white matter disease.

Vanishing white matter (VWM) disease, inherited in an autosomal recessive manner, is one of the most prevalent inherited leukoencephalopathies in childhood. It is a hereditary human disease resulting from the direct defects during protein synthesis, with the gene defects in EIF2B1-5 (identified in 2001-2002) encoding the five subunits of eukaryotic translation initiation factor (eIF2B alpha, beta, gamma, delta and epsilon), respectively. Most of the published studies were carried out in the white population. The analysis of clinical features and EIF2B mutation screening were performed in 11 Chinese patients for the first time. Mutations were identified exclusively in EIF2B5 and EIF2B3 in these patients, with six novel mutations, including five missense mutations (EIF2B5: c.185A>T, p.D62V; c.1004G>C, p.C335S; c.1126A>G, p.N376D; EIF2B3: c.140G>A, p.G47E; c.1037T>C, p.I346T) and one deletion leading to amino-acid deletion (EIF2B5: c.1827-1838del, p.S610-D613del). EIF2B3 mutation, accounting for 20% of the total number of mutations found in this study, is more prevalent than expected according to an earlier report (7%). A hot spot mutation in EIF2B3 was identified in this study. A unique EIF2B mutation spectrum in Chinese VWM patients was shown. A systemic study to assess mutation spectrum in different populations needs to be carried out.