ADGRV1 Variants in Febrile Seizures/Epilepsy With Antecedent Febrile Seizures and Their Associations With Audio-Visual Abnormalities

Genotypic and phenotypic characteristics of ADGRV1 mutations in four children and functional validation in a zebrafish model

Mutations in ADGRV1 can cause seizures, but the mechanism remains unclear. The zebrafish model can be used to assess the functions of human ADGRV1 and its variant alleles during embryonic development. In this study, we summarized the phenotypic and genotypic characteristics of four children with ADGRV1 variation and based on this, we validated the ADGRV1 loss phenotype in an adgrv1-knockout zebrafish model. We retrospectively analyzed the clinical and genotypic characteristics of four pediatric patients diagnosed as having ADGRV1 mutations at Children's Hospital Affiliated to Chongqing Medical University from April 2019 to February 2022. Moreover, we used the adgrv1-knockout zebrafish larvae model and performed morphological, behavioral, and neuroelectrophysiological testing. We found that of the four included children, two had epilepsy, one had paroxysmal kinesigenic dyskinesia, and one had febrile seizure plus. Three children had a history of febrile seizures, whereas two had a family history of febrile seizures. Three children had well-controlled clinical epilepsy seizures or motor disorders. Finally, one child with spontaneous mutation had epigenetic abnormalities and comprehensive developmental delay, one had language developmental delay, and two (paternal or maternal) had a good prognosis. Regarding the zebrafish model, the cas9-control and adgrv1-edited groups demonstrated significant differences in the interocular areas of the zebrafish observed in the open field and the maximum swimming velocity under light stimulus. In neuroelectrophysiological testing, epilepsy-related signals were observed in 2 of 26 adgrv1-edited group fish. We believe that, mutations in the ADGRV1 may lead to epileptic seizures and movement disorders. The patients usually have a history of febrile seizures or a family history. Through research using the zebrafish model, it has been found that ADGRV1 mutations can affect the expression of eye and the neuromotor development of zebrafish larvae. This might be one of the reasons for epileptic seizures caused by ADGRV1 gene mutations.

The BBS/CCT chaperonin complex ensures the localization of the adhesion G protein-coupled receptor ADGRV1 to the base of primary cilia

Primary cilia are antenna-like sensory organelles present on almost all eukaryotic cells. Their sensory capacity relies on receptors, in particular G-protein-coupled receptors (GPCRs) which localize to the ciliary membrane. Here we show that ADGRV1, a member of the GPCR subfamily of adhesion GPCRs, is part of a large protein network, interacting with numerous proteins of a comprehensive ciliary proteome. ADGRV1 is localized to the base of prototypic primary cilia in cultured cells and the modified primary cilia of retinal photoreceptors, where it interacts with TRiC/CCT chaperonins and the Bardet Biedl syndrome (BBS) chaperonin-like proteins. Knockdown of ADGRV1, CCT2 and 3, and BBS6 result in common ciliogenesis phenotypes, namely reduced ciliated cells combined with shorter primary cilia. In addition, the localization of ADGRV1 to primary cilia depends on the activity of a co-complex of TRiC/CCT chaperonins and the BBS chaperonin-like proteins. In the absence of components of the TRiC/CCT-BBS chaperonin co-complex, ADGRV1 is depleted from the base of the primary cilium and degraded via the proteasome. Defects in the TRiC/CCT-BBS chaperonin may lead to an overload of proteasomal degradation processes and imbalanced proteostasis. Dysfunction or absence of ADGRV1 from primary cilia may underly the pathophysiology of human Usher syndrome type 2 and epilepsy caused by mutations in ADGRV1.

Single-cell multiomics of neuronal activation reveals context-dependent genetic control of brain disorders

Despite hundreds of genetic risk loci identified for neuropsychiatric disorders (NPD), most causal variants/genes remain unknown. A major hurdle is that disease risk variants may act in specific biological contexts, e.g., during neuronal activation, which is difficult to study in vivo at the population level. Here, we conducted a single-cell multiomics study of neuronal activation (stimulation) in human iPSC-induced excitatory and inhibitory neurons from 100 donors, and uncovered abundant neuronal stimulation-specific causal variants/genes for NPD. We surveyed NPD-relevant transcriptomic and epigenomic landscape of neuronal activation and identified thousands of genetic variants associated with activity-dependent gene expression (i.e., eQTL) and chromatin accessibility (i.e., caQTL). These caQTL explained considerably larger proportions of NPD heritability than the eQTL. Integrating the multiomic data with GWAS further revealed NPD risk variants/genes whose effects were only detected upon stimulation. Interestingly, multiple lines of evidence support a role of activity-dependent cholesterol metabolism in NPD. Our work highlights the power of cell stimulation to reveal context-dependent "hidden" genetic effects.

ADGRL1 variants: From developmental and epileptic encephalopathy to genetic epilepsy with febrile seizures plus

AIM

To expand the phenotypic spectrum of ADGRL1 and explore the correlation between epilepsy and the ADGRL1 genotype.

METHOD

We performed whole-exome sequencing in a cohort of 115 families (including 195 males and 150 females) with familial febrile seizure or epilepsy with unexplained aetiology. The damaging effects of variants was predicted using protein modelling and multiple in silico tools. All reported patients with ADGRL1 pathogenic variants were analysed.

RESULTS

One new ADGRL1 variant (p.Pro753Leu) was identified in one family with genetic epilepsy with febrile seizures. Further analysis of 12 ADGRL1 variants in 16 patients revealed that six patients had epilepsy. Epilepsy types ranged from early-onset epileptic encephalopathy to genetic epilepsy with febrile seizures plus (GEFS+). All four variants associated with epilepsy were located in the non-helix or sheet region of ADGRL1. Three of the four epilepsy-associated variants were missense variants. Thus, all three variants located in the G-protein-coupled receptor autoproteolytic-inducing domain exhibited epilepsy.

INTERPRETATION

We found one new missense variant of ADGRL1 in one family with GEFS+. ADGRL1 may be a potential candidate or susceptibility gene for epilepsy. ADGRL1-associated epilepsy ranged from benign GEFS+ to severe epileptic encephalopathy; the genotypes and variant locations may help explain the phenotypic heterogeneity of patients with the ADGRL1 variant.

Investigating the Therapeutic Property of Galium verum L. (GV) for MSG induced Audiogenic Epilepsy (AEs) and Neuroprotection through In-Silico and In-Vitro Analysis

BACKGROUND

Audiogenic Epilepsy (AEs) is a subtype of epileptic seizure that is generally caused by high-intensity sounds. A large number of traditional medicines has been explored in this lieu where our study chased Galium verum L. (Rubiaceae), an herbal plant which is commonly known as Lady's Bedstraw, that contains a highly rich chemical composition including flavonoids (Hispidulin, Quercetin, and Kaempferol), and phenolic acids (chlorogenic acid, caftaric acid, and gallic acid). G verum is well known for its antioxidant, neuroprotective, and anti-inflammatory properties. Recently, the unique role of Adhesion G Protein- Coupled Receptor V1 (ADGRV1) protein in the progression of audiogenic epilepsy has been explored.

AIMS AND OBJECTIVES

This study aimed to examine the potent phytoconstituents of the hydroalcoholic extract of G. verum L. (HEGV) using analytical techniques. Additionally, our study sought to evaluate the antioxidant, neuroprotective, anti-inflammatory properties, and antiepileptic potency of HEGV by targeting ADGRV1 via in silico and in vitro analyses using SHSY5Y cells.

METHODS

HPLC and LC-MS techniques were employed to identify the flavonoids, iridoids, and phenolic acid derivatives present in HEGV. DPPH (2,2-diphenyl-1-picrylhydrazyl), nitric oxide (NO), and hydroxyl (OH) radical scavenging assays were performed to confirm the antioxidant potential of the extract. Additionally, in silico molecular docking and molecular dynamic studies were performed using AutoDock Vina software to analyze the possible interactions between crucial phytoconstituents of HEGV and ADGRV1, followed by cell line analysis. In the in vitro analysis, antioxidant, neuroprotective, and anti-inflammatory properties were assessed via cell viability assay, IL, GABA, and glutamate estimation.

RESULTS

LC-MS and HPLC analyses revealed high concentrations of hispidulin, a major flavonoid found in HEGV. HEGV exhibited moderate-to-high free radical-scavenging activities comparable to those of ascorbic acid. Docking analysis demonstrated that hispidulin has a stronger binding affinity with ADGRV1 (Vina score = -8.6 kcal/mol) than other compounds. Furthermore, cell line analysis revealed that the MSG exacerbates the neurodegeneration and neuroinflammation, whereas, HEGV and Hispidulin both possess neuroprotective, antioxidant, and antiepileptic activities.

CONCLUSION

HEGV and Hispidulin proved to be promising candidates for treating audiogenic epilepsy by modulating ADGRV1.

G protein-coupled receptor (GPCR) gene variants and human genetic disease

Genetic variations in the genes encoding G protein-coupled receptors (GPCRs) can disrupt receptor structure and function, which can result in human genetic diseases. Disease-causing mutations have been reported in at least 55 GPCRs for more than 66 monogenic diseases in humans. The spectrum of pathogenic and likely pathogenic variants includes loss of function variants that decrease receptor signaling on one extreme and gain of function that may result in biased signaling or constitutive activity, originally modeled on prototypical rhodopsin GPCR variants identified in retinitis pigmentosa, on the other. GPCR variants disrupt ligand binding, G protein coupling, accessory protein function, receptor desensitization and receptor recycling. Next generation sequencing has made it possible to identify variants of uncertain significance (VUS). We discuss variants in receptors known to result in disease and in silico strategies for disambiguation of VUS such as sorting intolerant from tolerant and polymorphism phenotyping. Modeling of variants has contributed to drug development and precision medicine, including drugs that target the melanocortin receptor in obesity and interventions that reverse loss of gonadotropin-releasing hormone receptor from the cell surface in idiopathic hypogonadotropic hypogonadism. Activating and inactivating variants of the calcium sensing receptor (CaSR) gene that are pathogenic in familial hypocalciuric hypercalcemia and autosomal dominant hypocalcemia have enabled the development of calcimimetics and calcilytics. Next generation sequencing has continued to identify variants in GPCR genes, including orphan receptors, that contribute to human phenotypes and may have therapeutic potential. Variants of the CaSR gene, some encoding an arginine-rich region that promotes receptor phosphorylation and intracellular retention, have been linked to an idiopathic epilepsy syndrome. Agnostic strategies have identified variants of the pyroglutamylated RF amide peptide receptor gene in intellectual disability and G protein-coupled receptor 39 identified in psoriatic arthropathy. Coding variants of the G protein-coupled receptor L1 (GPR37L1) orphan receptor gene have been identified in a rare familial progressive myoclonus epilepsy. The study of the role of GPCR variants in monogenic, Mendelian phenotypes has provided the basis of modeling the significance of more common variants of pharmacogenetic significance.

Spatially resolved single-cell atlas of ascidian endostyle provides insight into the origin of vertebrate pharyngeal organs

The pharyngeal endoderm, an innovation of deuterostome ancestors, contributes to pharyngeal development by influencing the patterning and differentiation of pharyngeal structures in vertebrates; however, the evolutionary origin of the pharyngeal organs in vertebrates is largely unknown. The endostyle, a distinct pharyngeal organ exclusively present in basal chordates, represents a good model for understanding pharyngeal organ origins. Using Stereo-seq and single-cell RNA sequencing, we constructed aspatially resolved single-cell atlas for the endostyle of the ascidian Styela clava. We determined the cell composition of the hemolymphoid region, which illuminates a mixed ancestral structure for the blood and lymphoid system. In addition, we discovered a cluster of hair cell-like cells in zone 3, which has transcriptomic similarity with the hair cells of the vertebrate acoustico-lateralis system. These findings reshape our understanding of the pharynx of the basal chordate and provide insights into the evolutionary origin of multiplexed pharyngeal organs.

G protein-coupled receptor-mediated autophagy in health and disease

G protein-coupled receptors (GPCRs) constitute the largest and most diverse superfamily of mammalian transmembrane proteins. These receptors are involved in a wide range of physiological functions and are targets for more than a third of available drugs in the market. Autophagy is a cellular process involved in degrading damaged proteins and organelles and in recycling cellular components. Deficiencies in autophagy are involved in a variety of pathological conditions. Both GPCRs and autophagy are essential in preserving homeostasis and cell survival. There is emerging evidence suggesting that GPCRs are direct regulators of autophagy. Additionally, autophagic machinery is involved in the regulation of GPCR signalling. The interplay between GPCR and autophagic signalling mechanisms significantly impacts on health and disease; however, there is still an incomplete understanding of the underlying mechanisms and therapeutic implications in different tissues and disease contexts. This review aims to discuss the interactions between GPCR and autophagy signalling. Studies on muscarinic receptors, beta-adrenoceptors, taste receptors, purinergic receptors and adhesion GPCRs are summarized, in relation to autophagy.

The adhesion G protein-coupled receptor VLGR1/ADGRV1 controls autophagy

VLGR1/ADGRV1 (very large G protein-coupled receptor-1) is the largest known adhesion G protein-coupled receptor. Mutations in VLGR1/ADGRV1 cause Usher syndrome (USH), the most common form of hereditary deaf-blindness, and have been additionally linked to epilepsy. Although VLGR1/ADGRV1 is almost ubiquitously expressed, little is known about the subcellular function and signalling of the VLGR1 protein and thus about mechanisms underlying the development of diseases. Using affinity proteomics, we identified key components of autophagosomes as putative interacting proteins of VLGR1. In addition, whole transcriptome sequencing of the retinae of the Vlgr1/del7TM mouse model revealed altered expression profiles of gene-related autophagy. Monitoring autophagy by immunoblotting and immunocytochemistry of the LC3 and p62 as autophagy marker proteins revealed evoked autophagy in VLGR1-deficient hTERT-RPE1 cells and USH2C patient-derived fibroblasts. Our data demonstrate the molecular and functional interaction of VLGR1 with key components of the autophagy process and point to an essential role of VLGR1 in the regulation of autophagy at internal membranes. The close association of VLGR1 with autophagy helps to explain the pathomechanisms underlying human USH and epilepsy related to VLGR1 defects.

Monitoring paxillin in astrocytes reveals the significance of the adhesion G protein coupled receptor VLGR1/ADGRV1 for focal adhesion assembly

VLGR1/ADGRV1 (very large G protein-coupled receptor-1) is the largest adhesion G protein-coupled receptor (aGPCR). Mutations in VLGR1/ADGRV1 are associated with human Usher syndrome, the most common form of deaf-blindness, and also with epilepsy in humans and mice. VLGR1 is expressed almost ubiquitously but is mainly found in the CNS and in the sensory cells of the eye and inner ear. Little is known about the pathogenesis of the diseases related to VLGR1. We previously identified VLGR1 as a vital component of focal adhesions (FAs) serving as a metabotropic mechanoreceptor controls cell spreading and migration. FAs are highly dynamic and turnover in response to internal and external signals. Here, we aimed to elucidate how VLGR1 participates in FA turnover. Nocodazole washouts and live cell imaging of paxillin-DsRed2 consistently showed that FA disassembly was not altered, but de novo assembly of FA was significantly delayed in Vlgr1-deficient astrocytes, indicating that VLGR1 is enrolled in FA assembly. In FRAP experiments, recovery rates were significantly reduced in Vlgr1-deficient FAs, indicating reduced turnover kinetics in VLGR1-deficient FAs. We showed that VLGR1 regulates cell migration by controlling the FA turnover during their assembly and expect novel insights into pathomechanisms related to pathogenic dysfunctions of VLGR1.

The long-term neurodevelopmental outcomes of febrile seizures and underlying mechanisms

Febrile seizures (FSs) are convulsions caused by a sudden increase in body temperature during a fever. FSs are one of the commonest presentations in young children, occurring in up to 4% of children between the ages of about 6 months and 5 years old. FSs not only endanger children's health, cause panic and anxiety to families, but also have many adverse consequences. Both clinical and animal studies show that FSs have detrimental effects on neurodevelopment, that cause attention deficit hyperactivity disorder (ADHD), increased susceptibility to epilepsy, hippocampal sclerosis and cognitive decline during adulthood. However, the mechanisms of FSs in developmental abnormalities and disease occurrence during adulthood have not been determined. This article provides an overview of the association of FSs with neurodevelopmental outcomes, outlining both the underlying mechanisms and the possible appropriate clinical biomarkers, from histological changes to cellular molecular mechanisms. The hippocampus is the brain region most significantly altered after FSs, but the motor cortex and subcortical white matter may also be involved in the development disorders induced by FSs. The occurrence of multiple diseases after FSs may share common mechanisms, and the long-term role of inflammation and γ-aminobutyric acid (GABA) system are currently well studied.

Identification of Novel Gene Variants in Children With Drug-Resistant Epilepsy: Expanding the Genetic Spectrum

BACKGROUND

Resistance to antiseizure drugs is an important problem in the treatment of individuals with epilepsy. Identifying the molecular etiology of drug-resistant epilepsy (DRE) is crucial for better management of epilepsy. Here, we explore the utility of whole exome sequencing (WES) in identifying causative gene variants in children with DRE.

METHODS

Forty-five children with DRE who underwent WES tests were included. Genetic examination of all patients included chromosomal analysis and clinical chromosomal microarray followed by WES. The identified variants by WES analysis were classified for pathogenicity based on the American College of Medical Genetics and Genomics guidelines and in silico protein prediction tools.

RESULTS

The overall diagnostic yield was 55.5% (25 of 45). A total of 26 variants spanning 22 genes were identified in 25 patients. Of note, only 19 of these genes were examined as novel. Ten patients (22.2%) had a pathogenic or likely pathogenic variant. There was a trend associated with a diagnostic genetic test result in girls compared with boys in DRE (P = 0.028).

CONCLUSION

Our findings expand the mutational spectrum of genes related to DRE. To form disease-specific treatment in children with DRE, the WES analysis should be included in the diagnostic algorithm because of its high diagnostic efficiency.