ARX-associated infantile epileptic-dyskinetic encephalopathy with responsiveness to valproate for controlling seizures and reduced activity of muscle mitochondrial complex IV

Further characterisation of ARX-related disorders in females due to inherited or de novo variants

The Aristaless-related homeobox (ARX) gene is located on the X chromosome and encodes a transcription factor that is essential for brain development. While the clinical spectrum of ARX-related disorders is well described in males, from X linked lissencephaly with abnormal genitalia syndrome to syndromic and non-syndromic intellectual disability (ID), its phenotypic delineation in females is incomplete. Carrier females in ARX families are usually asymptomatic, but ID has been reported in some of them, as well as in others with de novo variants. In this study, we collected the clinical and molecular data of 10 unpublished female patients with de novo ARX pathogenic variants and reviewed the data of 63 females from the literature with either de novo variants (n=10), inherited variants (n=33) or variants of unknown inheritance (n=20). Altogether, the clinical spectrum of females with heterozygous pathogenic ARX variants is broad: 42.5% are asymptomatic, 16.4% have isolated agenesis of the corpus callosum (ACC) or mild symptoms (learning disabilities, autism spectrum disorder, drug-responsive epilepsy) without ID, whereas 41% present with a severe phenotype (ie, ID or developmental and epileptic encephalopathy (DEE)). The ID/DEE phenotype was significantly more prevalent in females carrying de novo variants (75%, n=15/20) versus in those carrying inherited variants (27.3%, n=9/33). ACC was observed in 66.7% (n=24/36) of females who underwent a brain MRI. By refining the clinical spectrum of females carrying ARX pathogenic variants, we show that ID is a frequent sign in females with this X linked condition.

Transcription factors in microcephaly

Higher cognition in humans, compared to other primates, is often attributed to an increased brain size, especially forebrain cortical surface area. Brain size is determined through highly orchestrated developmental processes, including neural stem cell proliferation, differentiation, migration, lamination, arborization, and apoptosis. Disruption in these processes often results in either a small (microcephaly) or large (megalencephaly) brain. One of the key mechanisms controlling these developmental processes is the spatial and temporal transcriptional regulation of critical genes. In humans, microcephaly is defined as a condition with a significantly smaller head circumference compared to the average head size of a given age and sex group. A growing number of genes are identified as associated with microcephaly, and among them are those involved in transcriptional regulation. In this review, a subset of genes encoding transcription factors (e.g., homeobox-, basic helix-loop-helix-, forkhead box-, high mobility group box-, and zinc finger domain-containing transcription factors), whose functions are important for cortical development and implicated in microcephaly, are discussed.

Aristaless-Related Homeobox (ARX): Epilepsy Phenotypes beyond Lissencephaly and Brain Malformations

The Aristaless-related homeobox (ARX) transcription factor is involved in the development of GABAergic and cholinergic neurons in the forebrain. ARX mutations have been associated with a wide spectrum of neurodevelopmental disorders in humans and are responsible for both malformation (in particular lissencephaly) and nonmalformation complex phenotypes. The epilepsy phenotypes related to ARX mutations are West syndrome and X-linked infantile spasms, X-linked myoclonic epilepsy with spasticity and intellectual development and Ohtahara and early infantile epileptic encephalopathy syndrome, which are related in most of the cases to intellectual disability and are often drug resistant. In this article, we shortly reviewed current knowledge of the function of ARX with a particular attention on its consequences in the development of epilepsy during early childhood.

USE OF KETOGENIC DIET THERAPY IN EPILEPSY WITH MITOCHONDRIAL DYSFUNCTION: A SYSTEMATIC AND CRITICAL REVIEW

With the development of molecular techniques over time more than %60 of epilepsy has associated with mitochondrial (mt) dysfunction. Ketogenic diet (KD) has been used in the treatment of epilepsy since the 1920s. Aim. To evaluate the evidence behind KD in mt dysfunction in epilepsy. Methods. Databases PubMed, Google Scholar and MEDLINE were searched in an umbrella approach to 12 March 2021 in English. To identify relevant studies specific search strategies were devised for the following topics: (1) mitochondrial dysfunction (2) epilepsy (3) KD treatment. Results. From 1794 papers, 36 articles were included in analysis: 16 (%44.44) preclinical studies, 11 (%30.55) case reports, 9 (%25) clinical studies. In all the preclinic studies, KD regulated the number of mt profiles, transcripts of metabolic enzymes and encoding mt proteins, protected the mice against to seizures and had an anticonvulsant mechanism. Case reports and clinical trials have reported patients with good results in seizure control and mt functions, although not all of them give good results as well as preclinical. Conclusion. Healthcare institutions, researchers, neurologists, health promotion organizations, and dietitians should consider these results to improve KD programs and disease outcomes for mt dysfunction in epilepsy.

A Review of Targeted Therapies for Monogenic Epilepsy Syndromes

Genetic sequencing technologies have led to an increase in the identification and characterization of monogenic epilepsy syndromes. This increase has, in turn, generated strong interest in developing “precision therapies” based on the unique molecular genetics of a given monogenic epilepsy syndrome. These therapies include diets, vitamins, cell-signaling regulators, ion channel modulators, repurposed medications, molecular chaperones, and gene therapies. In this review, we evaluate these therapies from the perspective of their clinical validity and discuss the future of these therapies for individual syndromes.

Generation of an induced pluripotent stem cell line (OGHFUi001-A) from a type 1 early infantile epileptic encephalopathy with ARX mutation

Type 1 early infantile epileptic encephalopathy (EIEE1) is a severe early-onset epileptic encephalopathy with arrest of psychomotor development caused by hemizygous mutations in the ARX gene, which encodes a transcription factor in fundamental brain developmental processes. A human induced pluripotent stem cell (iPSC) line, termed as OGHFUi001-A, was generated using non-integrating episomal vector technique from peripheral blood mononuclear cells (PBMCs) of a 7-year-old male EIEE1 patient, who had a hemizygous (c.989G > T: p.R330L) mutation in the ARX gene. OGHFUi001-A offers a useful cell resource to investigate pathogenic mechanisms in EIEE1, as well as a cell-based model for drug development for EIEE1.

Protective role of vitamin B6 against mitochondria damage in Drosophila models of SCA3

Polyglutamine (polyQ)-mediated mitochondria damage is one of the prime causes of polyQ toxicity, which leads to the loss of neurons and the injury of non-neuronal cells. With the discovery of the crucial role of the gut-brain axis and gut microbes in neurological diseases, the relationship between visceral damage and neurological disorders has also received extensive attention. This study successfully simulated the polyQ mitochondrial damage model by expressing 78 or 84 polyglutamine-containing Ataxin3 proteins in Drosophila intestinal enterocytes. In vivo, polyQ expression can reduce mitochondrial membrane potential, mitochondrial DNA damage, abnormal mitochondrial morphology, and loose mitochondrial cristae. Expression profiles evaluated by RNA-seq showed that mitochondrial structural genes and functional genes (oxidative phosphorylation and tricarboxylic acid cycle-related) were significantly down-regulated. More importantly, Bioinformatic analyses demonstrated that pathological polyQ expression induced vitamin B6 metabolic pathways abnormality. Active vitamin B6 participates in hundreds of enzymatic reactions and is very important for maintaining mitochondria's activities. In the SCA3 Drosophila model, Vitamin B6 supplementation significantly suppressed ECs mitochondria damage in guts and inhibited cellular polyQ aggregates in fat bodies, indicating a promising therapeutic strategy for the treatment of polyQ. Taken together, our results reveal a crucial role for the Vitamin B6-mediated mitochondrial protection in polyQ-induced cellular toxicity, which provides strong evidence for this process as a drug target in polyQ diseases treatment.

Association of early-onset epileptic encephalopathy with involuntary movements - Case series and literature review

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Epileptic-dyskinetic encephalopathies are rare epileptic disorders characterized by EOEE with involuntary movement.

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The presence of involuntary movements in patients with EOEE caused by gene variants may be a key diagnostic symptom.

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Genetic diagnosis is useful and may provide a reference for treatment selection.

Epileptic-dyskinetic encephalopathies are rare epilepsies characterized by early-onset epileptic encephalopathies (EOEEs) with involuntary movement. Herein, we investigated the impact of gene variants in epileptic-dyskinetic encephalopathies. Four independent patients from four families who exhibited involuntary movements were recruited from Tokyo Metropolitan Neurological Hospital. The inclusion criteria were as follows: onset within 1 year after birth, frequent seizures, severe developmental delay and accompanying involuntary movements.

We detected four genetic mutations, including STXBP1, GNAO1, CYFIP2, and SCN8A variants. The involuntary movements were drug-resistant. However, pallidal electrocoagulation followed by gabapentin were partially effective in treating chorea and ballismus of the extremities in patients with GNAO1 variants, and perampanel partially suppressed seizures and involuntary movements in one patient with a SCN8A variant. Movement disorders are common to many neurodevelopmental disorders, including a variety of EOEEs. Although we could not establish a definitive correlation using genetic variants in patients with EOEE and movement disorders, involuntary movements in patients with EOEEs may be a key diagnostic finding. The usage of genetic variants could prove beneficial in the future as more patients are investigated with epileptic-dyskinetic encephalopathies.