Association of brain-derived neurotrophic factor (BDNF) and elongator protein complex 4 (ELP4) polymorphisms with benign epilepsy with centrotemporal spikes in a Greek population

The epitranscriptome in ageing and stress resistance: A systematic review

Modifications of RNA, collectively called the "epitranscriptome", might provide novel biomarkers and innovative targets for interventions in geroscience but are just beginning to be studied in the context of ageing and stress resistance. RNA modifications modulate gene expression by affecting translation initiation and speed, miRNA binding, RNA stability, and RNA degradation. Nonetheless, the precise underlying molecular mechanisms and physiological consequences of most alterations of the epitranscriptome are still only poorly understood. We here systematically review different types of modifications of rRNA, tRNA and mRNA, the methodology to analyze them, current challenges in the field, and human disease associations. Furthermore, we compiled evidence for a connection between individual enzymes, which install RNA modifications, and lifespan in yeast, worm and fly. We also included resistance to different stressors and competitive fitness as search criteria for genes potentially relevant to ageing. Promising candidates identified by this approach include RCM1/NSUN5, RRP8, and F33A8.4/ZCCHC4 that introduce base methylations in rRNA, the methyltransferases DNMT2 and TRM9/ALKBH8, as well as factors involved in the thiolation or A to I editing in tRNA, and finally the m⁶A machinery for mRNA.

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.

A Novel PRRT2 Variant in Chinese Patients Suffering from Paroxysmal Kinesigenic Dyskinesia with Infantile Convulsion

PRRT2 mutations are the major causative agent of paroxysmal kinesigenic dyskinesia with infantile convulsion (PKD/IC). The study is aimed at screening PRRT2 gene mutations in patients who suffered from PKD/IC in Chinese population. Thirteen Chinese patients with PKD/IC were screened randomly for coding exons of the PRRT2 gene mutation along with 50 ethnically coordinated control people. Nine (2 unaffected) and 4 of the patients showed familial PKD/IC and apparently sporadic cases, respectively. We identified 5 different PRRT2 mutations in 10 individuals, including 8 familial and 2 apparently sporadic cases. However, no mutations were found in the 50 ethnically matched controls. Unknown (novel) NM_145239.2:c.686G>A and previously reported NM_145239.2:c.743G>C variants were identified in two familial and sporadic patients. All affected members of family A showed mutation NM_145239.2:c.650_670delinsCAATGGTGCCACCACTGGGTTA. The previously identified NM_145239.2:c.412 C>G and NM_145239.2:c.709G>A variants are seen in two individuals assessed in family B. Other than the previously identified variants, some of the patients with PRRT2-PKD/IC showed a new PRRT2 substitution variant. Thus, the spectrum of PRRT2 variants is expanded. The possible role and probability of PRRT2 variants involved in PKD/IC are highlighted.

Sleep Related Epilepsy and Pharmacotherapy: An Insight

In the last several decades, sleep-related epilepsy has drawn considerable attention among epileptologists and neuroscientists in the interest of new paradigms of the disease etiology, pathogenesis and management. Sleep-related epilepsy is nocturnal seizures that manifest solely during the sleep state. Sleep comprises two distinct stages i.e., non-rapid eye movement (NREM) and rapid eye movement (REM) that alternate every 90 min with NREM preceding REM. Current findings indicate that the sleep-related epilepsy manifests predominantly during the synchronized stages of sleep; NREM over REM stage. Sleep related hypermotor epilepsy (SHE), benign partial epilepsy with centrotemporal spikes or benign rolandic epilepsy (BECTS), and Panayiotopoulos Syndrome (PS) are three of the most frequently implicated epilepsies occurring during the sleep state. Although some familial types are described, others are seemingly sporadic occurrences. In the present review, we aim to discuss the predominance of sleep-related epilepsy during NREM, established familial links to the pathogenesis of SHE, BECTS and PS, and highlight the present available pharmacotherapy options.

Benign epilepsy with centrotemporal spikes - Current concepts of diagnosis and treatment

Benign epilepsy with centrotemporal spikes (BECTS) is the most common focal epilepsy of the childhood and also one of the best known. It has a proclivity to start at a particular age and remit spontaneously before adolescence. Majority of patients may avoid long-term treatment, because of the mild course and very good outcome. Only few patients may present cognitive deficits if the proper treatment is not implied. BECTS is a part of heterogeneous group of syndromes that consists of Landau-Kleffner Syndrome (LKS), Continuous Spike-and-Wave during Sleep (CSWS) and Atypical benign partial epilepsy (ABPE). These syndromes may be also a result of various trajectories that BECTS may evolve to. Disease is suggested to have genetic origins, as some patients have relatives with different types of epilepsy. The discovery of the pathogenic mechanism of the disease and implementation of targeted therapy belong to the main challenges in the treatment of these patients.

Key issues in Rett syndrome: emotional, behavioural and autonomic dysregulation (EBAD) - a target for clinical trials

Complex neurodevelopmental disorders need multi-disciplinary treatment approaches for optimal care. The clinical effectiveness of treatments is limited in patients with rare genetic syndromes with multisystem morbidity. Emotional and behavioural dysregulation is common across many neurodevelopmental disorders. It can manifest in children across multiple diagnostic groups, including those on the autism spectrum and in rare genetic syndromes such as Rett Syndrome (RTT). There is, however a remarkable scarcity in the literature on the impact of the autonomic component on emotional and behavioural regulation in these disorders, and on the longer-term outcomes on disorder burden.RTT is a debilitating and often life-threatening disorder involving multiple overlapping physiological systems. Autonomic dysregulation otherwise known as dysautonomia is a cardinal feature of RTT characterised by an imbalance between the sympathetic and parasympathetic arms of the autonomic nervous system. Unlocking the autonomic component of emotional and behavioural dysregulation would be central in reducing the impairment seen in patients with RTT. In this vein, Emotional, Behavioural and Autonomic Dysregulation (EBAD) would be a useful construct to target for treatment which could mitigate burden and improve the quality of life of patients.RTT can be considered as a congenital dysautonomia and because EBAD can give rise to impairments occurring in multiple overlapping physiological systems, understanding these physiological responses arising out of EBAD would be a critical part to consider when planning treatment strategies and improving clinical outcomes in these patients. Biometric guided pharmacological and bio-feedback therapy for the behavioural and emotional aspects of the disorder offers an attracting perspective to manage EBAD in these patients. This can also allow for the stratification of patients into clinical trials and could ultimately help streamline the patient care pathway for optimal outcomes.The objectives of this review are to emphasise the key issues relating to the management of EBAD in patients with RTT, appraise clinical trials done in RTT from the perspective of autonomic physiology and to discuss the potential of EBAD as a target for clinical trials.

Retina-specific loss of Ikbkap/Elp1 causes mitochondrial dysfunction that leads to selective retinal ganglion cell degeneration in a mouse model of familial dysautonomia

Familial dysautonomia (FD) is an autosomal recessive disorder marked by developmental and progressive neuropathies. It is caused by an intronic point-mutation in the IKBKAP/ELP1 gene, which encodes the inhibitor of κB kinase complex-associated protein (IKAP, also called ELP1), a component of the elongator complex. Owing to variation in tissue-specific splicing, the mutation primarily affects the nervous system. One of the most debilitating hallmarks of FD that affects patients' quality of life is progressive blindness. To determine the pathophysiological mechanisms that are triggered by the absence of IKAP in the retina, we generated retina-specific Ikbkap conditional knockout (CKO) mice using Pax6-Cre, which abolished Ikbkap expression in all cell types of the retina. Although sensory and autonomic neuropathies in FD are known to be developmental in origin, the loss of IKAP in the retina did not affect its development, demonstrating that IKAP is not required for retinal development. The loss of IKAP caused progressive degeneration of retinal ganglion cells (RGCs) by 1 month of age. Mitochondrial membrane integrity was breached in RGCs, and later in other retinal neurons. In Ikbkap CKO retinas, mitochondria were depolarized, and complex I function and ATP were significantly reduced. Although mitochondrial impairment was detected in all Ikbkap-deficient retinal neurons, RGCs were the only cell type to degenerate; the survival of other retinal neurons was unaffected. This retina-specific FD model is a useful in vivo model for testing potential therapeutics for mitigating blindness in FD. Moreover, our data indicate that RGCs and mitochondria are promising targets.

Summary: The elongator subunit IKBKAP/ELP1 is not required for development, but is essential for maintaining mitochondrial function and retina morphology. Loss of this subunit causes progressive, selective degeneration of retinal ganglion cells.

Elongator complex is required for long-term olfactory memory formation in Drosophila

The evolutionarily conserved Elongator Complex associates with RNA polymerase II for transcriptional elongation. Elp3 is the catalytic subunit, contains histone acetyltransferase activity, and is associated with neurodegeneration in humans. Elp1 is a scaffolding subunit and when mutated causes familial dysautonomia. Here, we show that elp3 and elp1 are required for aversive long-term olfactory memory in Drosophila RNAi knockdown of elp3 in adult mushroom bodies impairs long-term memory (LTM) without affecting earlier forms of memory. RNAi knockdown with coexpression of elp3 cDNA reverses the impairment. Similarly, RNAi knockdown of elp1 impairs LTM and coexpression of elp1 cDNA reverses this phenotype. The LTM deficit in elp3 and elp1 knockdown flies is accompanied by the abolishment of a LTM trace, which is registered as increased calcium influx in response to the CS+ odor in the α-branch of mushroom body neurons. Coexpression of elp1 or elp3 cDNA rescues the memory trace in parallel with LTM. These data show that the Elongator complex is required in adult mushroom body neurons for long-term behavioral memory and the associated long-term memory trace.

Significant association of BDNF rs6265 G>A polymorphism with susceptibility to epilepsy: a meta-analysis

INTRODUCTION

Previously published articles have suggested that BDNF rs6265 G>A polymorphism is a potential risk factor for epilepsy. However, the results were not consistent.

METHODS

We conducted a meta-analysis to explore the association between BDNF rs6265 G>A polymorphism and epilepsy risk. Four online databases were searched, and related studies were reviewed from their inception up to June 20, 2017. ORs and corresponding 95% CIs were used to calculate the associations of each genetic model. Overall, 10 case-control publications involving 9,512 subjects were included in this meta-analysis.

RESULTS

Significant associations were found between BDNF rs6265 G>A polymorphism and epilepsy (A vs G: OR=0.88, 95% CI=0.83-0.94, P<0.01, I²=0%; GA vs GG: OR=0.88, 95% CI=0.79-0.97, P=0.01, I²=0%; AA vs GG: OR=0.79, 95% CI=0.70-0.90, P<0.01, I²=0%; GA+AA vs GG: OR=0.85, 95% CI=0.77-0.94, P<0.01, I²=0%; AA vs GG+GA: OR=0.85, 95% CI=0.76-0.95, P=0.01, I²=0%). Subgroup analysis also showed similar results in an Asian population.

CONCLUSION

Our meta-analysis indicated that BDNF rs6265 G>A polymorphism might be involved in epilepsy susceptibility, especially in the Asian population.

NTRK2 (TrkB gene) variants and temporal lobe epilepsy: A genetic association study

OBJECTIVE

The NTRK2 gene encodes a member of the neurotrophic tyrosine kinase receptor family known as TrkB. It is a membrane-associated receptor with signaling and cellular differentiation properties that has been involved in neuropsychiatric disorders, including epilepsy. We report here the frequencies of NTRK2 allele variants in patients with temporal lobe epilepsy (TLE) compared to controls without epilepsy and explore the impact of these polymorphisms on major clinical variables in TLE.

METHODS

A case-control study comparing the frequencies of the NTRK2 gene polymorphisms beween 198 TLE Caucasian patients and 200 matching controls without epilepsy. In a second step, the impact of allelic variation on major clinical and electroencephalographic epilepsy variables was evaluated in the group of TLE patients. The following polymorphisms were determined by testing different regions of the NTRK2 gene: rs1867283, rs10868235, rs1147198, rs11140800, rs1187286, rs2289656, rs1624327, rs1443445, rs3780645, and rs2378672. To correct for multiple correlations the level of significance was set at p<0.01.

RESULTS

Patients with TLE showed a statistical trend for increase of the T/T genotype in rs10868235 compared to control (O.R.=1.90; 95%CI=1.17-3.09; p=0.01). Homozygous patients for the A allele in rs1443445 had earlier mean age at onset of seizures, p=0.009 (mean age of 16.6 versus 22.4years). We also observed that the T allele in rs3780645 was more frequent in patients who needed polytheraphy for seizure control than in patients on monotherapy, (O.R.=4.13; 95%CI=1.68-10.29; p=0.001). This finding may reflect an increased difficulty to obtain seizure control in this group of patients. No additional differences were observed in this study.

CONCLUSIONS

Patients with epilepsy showed a trend for a difference in rs10868235 allelic distribution compared to controls without epilepsy. NTRK2 variability influenced age at seizure onset and the pharmacological response to seizure control. As far as we know, this is the first study showing an association between NTKR2 allelic variants in human epilepsy. We believe that further studies in this venue will shade some light on the molecular mechanisms involved in epileptogenesis and in the clinical characteristics of epilepsy.

Animal and cellular models of familial dysautonomia

Since Riley and Day first described the clinical phenotype of patients with familial dysautonomia (FD) over 60 years ago, the field has made considerable progress clinically, scientifically, and translationally in treating and understanding the etiology of FD. FD is classified as a hereditary sensory and autonomic neuropathy (HSAN type III) and is both a developmental and a progressive neurodegenerative condition that results from an autosomal recessive mutation in the gene IKBKAP, also known as ELP1. FD primarily impacts the peripheral nervous system but also manifests in central nervous system disruption, especially in the retina and optic nerve. While the disease is rare, the rapid progress being made in elucidating the molecular and cellular mechanisms mediating the demise of neurons in FD should provide insight into degenerative pathways common to many neurological disorders. Interestingly, the protein encoded by IKBKAP/ELP1, IKAP or ELP1, is a key scaffolding subunit of the six-subunit Elongator complex, and variants in other Elongator genes are associated with amyotrophic lateral sclerosis (ALS), intellectual disability, and Rolandic epilepsy. Here we review the recent model systems that are revealing the molecular and cellular pathophysiological mechanisms mediating FD. These powerful model systems can now be used to test targeted therapeutics for mitigating neuronal loss in FD and potentially other disorders.

Progress in unraveling the genetic etiology of rolandic epilepsy

Rolandic epilepsy (RE), or benign epilepsy of childhood with centrotemporal spikes (BECT), is the most frequent idiopathic partial epilepsy syndrome of childhood, where the "idiopathic" implies a genetic predisposition. Although RE has long been presumed to have a genetic component, clinical and genetic studies have shown a complex inheritance pattern. Furthermore, the underlying major genetic influence in RE has been challenged by recent reports of twin studies. Meanwhile, many genes or loci have been shown to be associated the RE/atypical RE (ARE) spectrum, with a higher frequency of causative variants in ARE. However, a full understanding of the genetic basis in the more common forms of the RE spectrum remains elusive.

The familial dysautonomia disease gene IKBKAP is required in the developing and adult mouse central nervous system

Hereditary sensory and autonomic neuropathies (HSANs) are a genetically and clinically diverse group of disorders defined by peripheral nervous system (PNS) dysfunction. HSAN type III, known as familial dysautonomia (FD), results from a single base mutation in the gene IKBKAP that encodes a scaffolding unit (ELP1) for a multi-subunit complex known as Elongator. Since mutations in other Elongator subunits (ELP2 to ELP4) are associated with central nervous system (CNS) disorders, the goal of this study was to investigate a potential requirement for Ikbkap in the CNS of mice. The sensory and autonomic pathophysiology of FD is fatal, with the majority of patients dying by age 40. While signs and pathology of FD have been noted in the CNS, the clinical and research focus has been on the sensory and autonomic dysfunction, and no genetic model studies have investigated the requirement for Ikbkap in the CNS. Here, we report, using a novel mouse line in which Ikbkap is deleted solely in the nervous system, that not only is Ikbkap widely expressed in the embryonic and adult CNS, but its deletion perturbs both the development of cortical neurons and their survival in adulthood. Primary cilia in embryonic cortical apical progenitors and motile cilia in adult ependymal cells are reduced in number and disorganized. Furthermore, we report that, in the adult CNS, both autonomic and non-autonomic neuronal populations require Ikbkap for survival, including spinal motor and cortical neurons. In addition, the mice developed kyphoscoliosis, an FD hallmark, indicating its neuropathic etiology. Ultimately, these perturbations manifest in a developmental and progressive neurodegenerative condition that includes impairments in learning and memory. Collectively, these data reveal an essential function for Ikbkap that extends beyond the peripheral nervous system to CNS development and function. With the identification of discrete CNS cell types and structures that depend on Ikbkap, novel strategies to thwart the progressive demise of CNS neurons in FD can be developed.

Summary:Ikbkap is essential for normal CNS development, neuronal survival and behavior, adding to our understanding of the role of the Elongator complex in the mammalian CNS.

Association of BDNF Polymorphisms with the Risk of Epilepsy: a Multicenter Study

Epilepsy is a common neurological disease characterized by recurrent unprovoked seizures. Evidence suggested that abnormal activity of brain-derived neurotrophic factor (BDNF) contributes to the pathogenesis of epilepsy. Some previous studies identified association between genetic variants of BDNF and risk of epilepsy. In this study, this association has been examined in the Hong Kong and Malaysian epilepsy cohorts. Genomic DNA of 6047 subjects (1640 patients with epilepsy and 4407 healthy individuals) was genotyped for rs6265, rs11030104, rs7103411, and rs7127507 polymorphisms by using Sequenom MassArray and Illumina HumanHap 610-Quad or 550-Duo BeadChip arrays techniques. Results showed significant association between rs6265 T, rs7103411 C, and rs7127507 T and cryptgenic epilepsy risk (p = 0.00003, p = 0.0002, and p = 0.002, respectively) or between rs6265 and rs7103411 and symptomatic epilepsy risk in Malaysian Indians (TT vs. CC, p = 0.004 and T vs. C, p = 0.0002, respectively) as well as between rs6265 T and risk of cryptogenic epilepsy in Malaysian Chinese (p = 0.005). The Trs6265-Crs7103411-Trs7127507 was significantly associated with cryptogenic epilepsy in Malaysian Indians (p = 0.00005). In conclusion, our results suggest that BDNF polymorphisms might contribute to the risk of epilepsy in Malaysian Indians and Chinese.