The Study of Genetic Susceptibility and Mitochondrial Dysfunction in Mesial Temporal Lobe Epilepsy

A Novel m.1636A > G Variant in Mitochondrial TV Gene Might Cause New Phenotype of Mitochondrial Disease in a 2-Year Old Chinese Boy

Pathogenic variants of mitochondrial DNA (mtDNA) are associated with a large number of heterogeneous diseases involving multiple systems with which patients may present with a wide range of clinical phenotypes. Clinical data of the proband and his family members were gathered in a retrospective study. Whole-exome sequencing and full-length sequencing of the mitochondrial genome that was performed on peripheral blood, urine, and oral mucosa cells were applied for genetic analysis. In this study, we describe a 2-year-old Chinese boy with global developmental delay, Charcot-Marie-Tooth (CMT) disease, progressive myoclonic epilepsy, paroxysmal arrhythmia, and brain atrophy with elevated blood lactate levels. The clinical manifestations of the patient were improved after metabolic therapy, but the development regressed after infection. The molecular finding of whole-exome sequencing is unremarkable, but the mtDNA genome sequencing of the proband and his monther revealed a de novo novel heteroplasmic variant, m.1636A > G, located next to the highly conserved anticodon loop of tRNA Val (MT-TV) gene. Moreover, the higher levels of mutational load in urinary epithelial cells (19.05%) and oral mucosa cells (20.8%) were detected than that in blood (17.4%). Combined with the phenotypic and molecular genetics analysis of this family, this novel variation was currently considered to be a likely pathogenic variant. Our results added evidence that the de novo m.1636A > G variation in the highly conserved sequence of MT-TV appears to suggest a childhood-onset mitochondrial phenotype of a 2-year-old patient, thus broaden the genotypic interpretation of mitochondrial DNA-related disease.

Cerebellar white and gray matter abnormalities in temporal lobe epilepsy: a voxel-based morphometry study

Background

Previous structural neuroimaging studies linked cerebellar deficits to temporal lobe epilepsy (TLE). The functions of various cerebellar regions are increasingly being valued, and their changes in TLE patients warrant further in-depth investigation. In this study, we used the Spatially Unbiased Infratentorial (SUIT) toolbox with a new template to evaluate the cerebellar structural abnormalities in patients with TLE, and further explored the relationship between the changes of different cerebellar regions and cognition.

Methods

Thirty-two patients with TLE were compared with 39 healthy controls (HC) matched according to age, gender, handedness, and education level. All participants underwent a high-resolution T1-weighted MRI scan on a 3.0 Tesla scanner. We used a voxel-based morphometry (VBM) approach utilizing the SUIT toolbox to provide an optimized and fine-grained exploration of cerebellar structural alterations associated with TLE.

Results

Compared with HC, TLE patients showed a significant reduction in the volume of gray matter in the Left lobule VI and white matter in the Right Crus II. In the TLE patient group, we conducted partial correlation analysis between the volumes of different cerebellar regions and cognitive rating scale scores, such as MMSE and MoCA. The volume of the Left lobule VI (GM) exhibited a positive correlation with the MMSE score, but no significant correlation was found with the MoCA score. On the other hand, there was no significant correlation observed between the volume of the Right Crus II (WM) and the two cognitive scale scores mentioned above. Furthermore, it was observed that the MMSE was more effective than the MoCA in identifying epilepsy patients with cognitive impairment.

Conclusion

This study supported previous research indicating that temporal lobe epilepsy (TLE) is linked to structural changes in the cerebellum, specifically affecting the volume of both gray and white matter. These findings offer valuable insights into the neurobiology of TLE and hold potential to inform the development of enhanced diagnostic methods and more effective treatment approaches.

Molecular Genetics of Acquired Temporal Lobe Epilepsy

An epilepsy diagnosis reduces a patient's quality of life tremendously, and it is a fate shared by over 50 million people worldwide. Temporal lobe epilepsy (TLE) is largely considered a nongenetic or acquired form of epilepsy that develops in consequence of neuronal trauma by injury, malformations, inflammation, or a prolonged (febrile) seizure. Although extensive research has been conducted to understand the process of epileptogenesis, a therapeutic approach to stop its manifestation or to reliably cure the disease has yet to be developed. In this review, we briefly summarize the current literature predominately based on data from excitotoxic rodent models on the cellular events proposed to drive epileptogenesis and thoroughly discuss the major molecular pathways involved, with a focus on neurogenesis-related processes and transcription factors. Furthermore, recent investigations emphasized the role of the genetic background for the acquisition of epilepsy, including variants of neurodevelopmental genes. Mutations in associated transcription factors may have the potential to innately increase the vulnerability of the hippocampus to develop epilepsy following an injury-an emerging perspective on the epileptogenic process in acquired forms of epilepsy.

A novel mutation of DNA2 regulates neuronal cell membrane potential and epileptogenesis

Mesial temporal lobe epilepsy (MTLE) is one of the most intractable epilepsies. Previously, we reported that mitochondrial DNA deletions were associated with epileptogenesis. While the underlying mechanism of mitochondrial DNA deletions during epileptogenesis remain unknown. In this study, a novel somatic mutation of DNA2 gene was identified in the hippocampal tissue of two MTLE patients carrying mitochondrial DNA deletions, and this mutation decreased the full-length expression of DNA2 protein significantly, aborting its normal functions. Then, we knocked down the DNA2 protein in zebrafish, and we demonstrated that zebrafish with DNA2 deficiency showed decreased expression of mitochondrial complex II-IV, and exhibited hallmarks of epileptic seizures, including abnormal development of the zebrafish and epileptiform discharge signals in brain, compared to the Cas9-control group. Moreover, our cell-based assays showed that DNA2 deletion resulted in accumulated mitochondrial DNA damage, abnormal oxidative phosphorylation and decreased ATP production in cells. Inadequate ATP generation in cells lead to declined Na+, K+-ATPase activity and change of cell membrane potential. Together, these disorders caused by DNA2 depletion increased cell apoptosis and inhibited the differentiation of SH-SY5Y into branched neuronal phenotype. In conclusion, DNA2 deficiency regulated the cell membrane potential via affecting ATP production by mitochondria and Na+, K+-ATPase activity, and also affected neuronal cell growth and differentiation. These disorders caused by DNA2 dysfunction are important causes of epilepsy. In summary, we are the first to report the pathogenic somatic mutation of DNA2 gene in the patients with MTLE disease, and we uncovered the mechanism of DNA2 regulating the epilepsy. This study provides new insight into the pathogenesis of epilepsy and underscore the value of DNA2 in epilepsy.

Thyroid function and epilepsy: a two-sample Mendelian randomization study

Background

Thyroid hormones (THs) play a crucial role in regulating various biological processes, particularly the normal development and functioning of the central nervous system (CNS). Epilepsy is a prevalent neurological disorder with multiple etiologies. Further in-depth research on the role of thyroid hormones in epilepsy is warranted.

Methods

Genome-wide association study (GWAS) data for thyroid function and epilepsy were obtained from the ThyroidOmics Consortium and the International League Against Epilepsy (ILAE) Consortium cohort, respectively. A total of five indicators of thyroid function and ten types of epilepsy were included in the analysis. Two-sample Mendelian randomization (MR) analyses were conducted to investigate potential causal relations between thyroid functions and various epilepsies. Multiple testing correction was performed using Bonferroni correction. Heterogeneity was calculated with the Cochran's Q statistic test. Horizontal pleiotropy was evaluated by the MR-Egger regression intercept. The sensitivity was also examined by leave-one-out strategy.

Results

The findings indicated the absence of any causal relationship between abnormalities in thyroid hormone and various types of epilepsy. The study analyzed the odds ratio (OR) between thyroid hormones and various types of epilepsy in five scenarios, including free thyroxine (FT4) on focal epilepsy with hippocampal sclerosis (IVW, OR = 0.9838, p = 0.02223), hyperthyroidism on juvenile absence epilepsy (IVW, OR = 0.9952, p = 0.03777), hypothyroidism on focal epilepsy with hippocampal sclerosis (IVW, OR = 1.0075, p = 0.01951), autoimmune thyroid diseases (AITDs) on generalized epilepsy in all documented cases (weighted mode, OR = 1.0846, p = 0.0346) and on childhood absence epilepsy (IVW, OR = 1.0050, p = 0.04555). After Bonferroni correction, none of the above results showed statistically significant differences.

Conclusion

This study indicates that there is no causal relationship between thyroid-related disorders and various types of epilepsy. Future research should aim to avoid potential confounding factors that might impact the study.

Eucommiae Folium and Active Compounds Protect Against Mitochondrial Dysfunction-Calcium Overload in Epileptic Hippocampal Neurons Through the Hypertrophic Cardiomyopathy Pathway

Epilepsy is a chronic brain disease and often occurs suddenly for no reason. Eucommiae folium (EF), an edible herb, can be used in the treatment of various kinds of brain diseases in clinic. From the perspective of safety and efficacy, EF is especially suitable for the treatment of chronic brain diseases. With the help of biolabels, this study was aimed to explore the value and feasibility of EF in the treatment of epilepsy. Proteomics and metabolomics were used to explore the biolabels of EF intervention in brain tissues. Bioinformatics was then applied to topologically analyze its neuroprotective effects and mechanisms and material basis based on biolabels, which were validated in an animal model. The biolabel-led research revealed that EF may exert the therapeutic potential to treat brain diseases through the interaction between multiple compounds and multiple targets, among which its therapeutic potential for epilepsy is particularly prominent. In the pentylenetetrazole-induction model, EF and four active compounds (oleamide, catechol, chlorogenic acid, and kaempferol) protected epileptic hippocampal neurons (Nissl and FJB staining) against mitochondrial dysfunction (MYH6, MYL3, and MYBPC3, etc.) and calcium overload (TNNI3, TNNC1, and TNNT2, etc.) through the hypertrophic cardiomyopathy pathway. This study provides new evidence and insights for the neuroprotective effects of EF, in which four active compounds may be potential drug candidates for the treatment of epilepsy.

Analysis of clinical phenotypic and genotypic spectra in 36 children patients with Epilepsy of Infancy with Migrating Focal Seizures

Epilepsy of Infancy with Migrating Focal Seizures (EIMFS) is a rare developmental and epileptic encephalopathy (DEEs) with unknown etiology, and poor prognosis. In order to explore new genetic etiology of EIMFS and new precision medicine treatment strategies, 36 children with EIMFS were enrolled in this study. 17/36 cases had causative variants across 11 genes, including 6 novel EIMFS genes: PCDH19, ALDH7A1, DOCK6, PRRT2, ALG1 and ATP7A. 13/36 patients had ineffective seizure control, 14/36 patients had severe retardation and 6/36 patients died. Of them, the genes for ineffective seizure control, severe retardation or death include KCNT1, SCN2A, SCN1A, ALG1, ATP7A and WWOX. 17 patients had abnormal MRI, of which 8 had ineffective seizure control, 7 had severe retardation and 4 died. 13 patients had hypsarrhythmia, of which 6 had ineffective seizure control, 6 had severe retardation and 2 died. Also, 7 patients had burst suppression, of which 1 had ineffective seizure control, 3 had severe retardation and 3 died. This study is the first to report that ALDH7A1, ATP7A, DOCK6, PRRT2, ALG1, and PCDH19 mutations cause the phenotypic spectrum of EIMFS to expand the genotypic spectrum. The genes KCNT1, SCN2A, SCN1A, ALG1, ATP7A and WWOX may be associated with poor prognosis. The patients presenting with MRI abnormalities, hypsarrhythmia and burst suppression in EEG may be associated with poor prognosis.

ARHGEF9 gene variant leads to developmental and epileptic encephalopathy: Genotypic phenotype analysis and treatment exploration

Background

The ARHGEF9 gene variants have phenotypic heterogeneity, the number of reported clinical cases are limited and the genotype–phenotype relationship is still unpredictable.

Methods

Clinical data of the patients and their family members were gathered in a retrospective study. The exome sequencing that was performed on peripheral blood samples was applied for genetic analysis. We used the ARHGEF9 gene as a key word to search the PubMed database for cases of ARHGEF9 gene variants that have previously been reported and summarized the reported ARHGEF9 gene variant sites, their corresponding clinical phenotypes, and effective treatment.

Results

We described five patients with developmental and epileptic encephalopathy caused by ARHGEF9 gene variants. Among them, the antiepileptic treatment of valproic acid and levetiracetam was effective in two cases individually. The exome sequencing results showed five children with point mutations in the ARHGEF9 gene: p.R365H, p.M388V, p.D213E, and p.R63H. So far, a total of 40 children with ARHGEF9 gene variants have been reported. Their main clinical phenotypes include developmental delay, epilepsy, epileptic encephalopathy, and autism spectrum disorders. The variants reported in the literature, including 22 de novo variants, nine maternal variants, and one unknown variant. There were 20 variants associated with epileptic phenotypes, of which six variants are effective for valproic acid treatment.

Conclusion

The genotypes and phenotypes of ARHGEF9 gene variants represent a wide spectrum, and the clinical phenotype of epilepsy is often refractory and the prognosis is poor. The p.R365H, p.M388V, p.D213E, and p.R63H variants have not been reported in the current literature, and our study has expanded the genotype spectrum of ARHGEF9 gene. Our findings indicate that levetiracetam and valproic acid can effectively control seizures in children with epileptic phenotype caused by ARGHEF9 gene variations. These findings will help clinicians improve the level of diagnosis and treatment of the genetic disease.

Multisystem Mitochondrial Disease Associated With a Mare m.10000G>A Mitochondrial tRNAGly (MT-TG) Variant

Background

Mitochondrial diseases are clinically heterogeneous, can occur at any age, and can manifest with a wide range of clinical symptoms. They can involve any organ or tissue, characteristically involve multiple systems, typically affecting organs that are highly dependent on aerobic metabolism, and making a definitive molecular diagnosis of a mitochondrial disorder is challenging.

Methods

Clinical data of the proband and his family members were gathered in a retrospective study. Whole-exome sequencing and full-length sequencing of the mitochondrial genome that were performed on peripheral blood, urine, and oral mucosa cells were applied for genetic analysis.

Results

In this study, we reported a childhood-onset mitochondrial phenotype in a 13-year-old patient. Analysis of the next-generation sequencing data of the nuclear genome and the full-length sequencing of the mitochondrial genome revealed the rare m.10000G>A variant in MT-TG that was present at variable heteroplasmy levels across tissue types: 32.7% in the blood, 56.15% in urinary epithelial cells, and 27.3% in oral mucosa cells. No variant was found in the peripheral blood of his mother and sister. No pathogenic mutation of nDNA was found.

Conclusion

Our results added evidence that the de novo m.10000G>A variation in the highly conserved sequence of MT-TG appears to suggest a childhood-onset mitochondrial phenotype in the 13-year-old patient, thus broadening the genotypic interpretation of mitochondrial DNA-related diseases.

Heterozygous missense mutation of the RELN gene is one of the causes of epilepsy

OBJECTIVES

Genetic factors play an important role in the onset of epilepsy, and the involvement of the RELN gene was recently discovered. This paper reports a family with a history of epilepsy caused by a heterozygous missense mutation in the RELN gene.

METHODS

After a clear diagnosis was made in the proband with a family history of epilepsy, gene sequencing was performed on the proband and his family members.

RESULTS

The proband was a 19-year-old male who presented with general convulsions during sleep lasting for about 1 min and was relieved spontaneously. His father and grandmother also experienced seizures. The gene sequencing results of the proband, his mother, and his grandmother showed that both the proband and his grandmother carried the same heterozygous missense mutation in the RELN gene (c.7909 C > T), unlike the proband's mother.

DISCUSSION

Mutations in the RELN gene can lead to the occurrence of benign epilepsy, though the specific type of seizures that it can cause is still unclear, and may increase the susceptibility to epilepsy. In addition, it may have potential anticancer effects.

MORC2 gene de novo mutation leads to Charcot-Marie-Tooth disease type 2Z: A pediatric case report and literature review

RATIONALE

Mutations of the MORC2 gene have most commonly been associated with autosomal-dominant Charcot-Marie-Tooth disease type 2Z (CMT 2Z), while the impact of MORC2 mutations in CMT 2Z on neuronal biology and their phenotypic consequences in patients remain to be clarified.

PATIENT CONCERNS

We reported a 27-month-old child with a developmental lag of more than 1 year. He had progressive fatigue for 4 months, accompanied by dysphagia, choking while eating, and progressive aggravation. A genetic study revealed a de novo variant of MORC2, which has not yet been reported.

DIAGNOSIS

According to the child's clinical manifestations, genetic pattern, and American College of Medical Genetics and Genomics pathogenicity analysis, the patient was diagnosed with CMT 2Z caused by MORC2 gene mutation.

INTERVENTIONS

Mitochondrial cocktail therapy (arginine, vitamin B1 tablets, vitamin B2 tablets, coenzyme Q10 capsules, L-carnitine oral liquid, idebenone tablets, etc) was given.

OUTCOMES

Mitochondrial cocktail therapy did not significantly improve the child's condition, head magnetic resonance imaging lesions were not significantly improved at outpatient follow-up more than 1 month later, and the lesions were basically unchanged.

LESSONS

The clinical manifestations of the disease were similar to those of Leigh syndrome, and they were not significantly improved by cocktail therapy. This site has not been reported in the literature domestically or abroad, and the pathogenesis of CMT 2Z caused by this site mutation is indeed not related to mitochondrial dysfunction. Our study is helpful for clinicians with regard to the differential diagnosis of Leigh syndrome and CMT 2Z and improvement of clinicians' understanding of CMT 2Z disease.

Clinical Utility of Rapid Exome Sequencing Combined With Mitochondrial DNA Sequencing in Critically Ill Pediatric Patients With Suspected Genetic Disorders

Genetic disorders are a frequent cause of hospitalization, morbidity and mortality in pediatric patients, especially in the neonatal or pediatric intensive care unit (NICU/PICU). In recent years, rapid genome-wide sequencing (exome or whole genome sequencing) has been applied in the NICU/PICU. However, mtDNA sequencing is not routinely available in rapid genetic diagnosis programs, which may fail to diagnose mtDNA mutation-associated diseases. Herein, we explored the clinical utility of rapid exome sequencing combined with mtDNA sequencing in critically ill pediatric patients with suspected genetic disorders. Rapid clinical exome sequencing (CES) was performed as a first-tier test in 40 critically ill pediatric patients (aged from 6 days to 15 years) with suspected genetic conditions. Blood samples were also collected from the parents for trio analysis. Twenty-six patients presented with neuromuscular abnormalities or other systemic abnormalities, suggestive of suspected mitochondrial diseases or the necessity for a differential diagnosis of other diseases, underwent rapid mtDNA sequencing concurrently. A diagnosis was made in 18 patients (45.0%, 18/40); three cases with de novo autosomal dominant variants, ten cases with homozygous or compound heterozygous variants, three cases with hemizygous variants inherited from mother, three cases with heterozygous variants inherited from either parent, and one case with a mtDNA mutation. The 18 patients were diagnosed with metabolic (n = 7), immunodeficiency (n = 4), cardiovascular (n = 2), neuromuscular (n = 2) disorders, and others. Genetic testing reports were generated with a median time of 5 days (range, 3–9 days). Thirteen patients that were diagnosed had an available medical treatment and resulted in a positive outcome. We propose that rapid exome sequencing combined with mitochondrial DNA sequencing should be available to patients with suspected mitochondrial diseases or undefined clinical features necessary for making a differential diagnosis of other diseases.

Case Report: ISPD Gene Mutation Leads to Dystroglycanopathies: Genotypic Phenotype Analysis and Treatment Exploration

ISPD gene mutation-related diseases have high clinical and genetic heterogeneity, and no studies have yet reported any effective treatments. We describe six patients with dystroglycanopathies caused by ISPD gene mutations and analyze their genotypes and phenotypes to explore possible effective treatments. Our results confirm that the phenotype of limb-girdle muscular dystrophies can be easily misdiagnosed as Duchenne muscular dystrophy and that exon deletions of ISPD gene are relatively common. Moreover, low-dose prednisone therapy can improve patients' exercise ability and prolong survival and may be a promising new avenue for ISPD therapy.