STXBP1 encephalopathy is associated with awake bruxism

The Oral Findings and Dental Management of Patients with West Syndrome: A Case Series and Literature Review

Objectives: West syndrome (WS) is a rare disorder with an estimated prevalence of 1 in 4000 live births, characterized by infantile spasms, hypsarrhythmia, and psychomotor developmental impairment. The available information on dental care forWS patients remains limited. The aim of this study was to describe oral manifestations and dental management in a series of WS patients. Methods: Fourteen patients diagnosed with WS were evaluated, including 10 males and 4 females, aged 12-41 years. Medical and dental variables were collected for all patients. Results: The most frequent oral findings were poor oral hygiene (64.2%), gingivitis (64.2%), dental caries (57.1%), and bruxism/tooth wear (28.5%). Only one patient had dental fractures (due to trauma), and none exhibited drug-induced gingival enlargement. Initial dental treatment was carried out under general anesthesia in 42.3% of the patients. However, following desensitization, half of the patients showed improved behavior and were ultimately treated using non-pharmacological behavioral support techniques. Conclusions: This series represents the largest published to date on the dental aspects of WS. Dental treatment needs of WS patients are considerable, and their management is primarily determined by the degree of epilepsy control, the presence of comorbidities, and the level of cooperation. Nevertheless, these patients may benefit from desensitization strategies to improve their behavior. As subsequent sessions were conducted, the behavior of 1 in every 3 initially non-compliant patients showed significant improvement.

Sleep bruxism: The past, the present, and the future-evolution of a concept

BACKGROUND

The concept of sleep bruxism (SB) has evolved exponentially over the past several decades. Many theories and hypotheses have been proposed as to the definition, pathophysiology, and management of SB, from the early 1960s through the present. The role of peripheral factors, such as dental occlusion, in the pathogenesis of SB has been discarded.

TYPES OF STUDIES REVIEWED

The authors searched several electronic databases (ie, PubMed, Google Scholar, Web of Science, Embase, and Ovid MEDLINE) for studies on bruxism. The search was conducted from January 1961 through May 2023 and yielded 4,612 articles, of which 312 were selected for comprehensive review after eliminating duplicates and nonfocused articles.

RESULTS

There has been an evident progressive shift from the role of peripheral factors, such as dental occlusion, to more central factors, such as the involvement of a central pattern generator as well as the autonomic nervous system, in the genesis of bruxing movements. There is continued robust interest in the dental community to elucidate the contributing factors involved in SB.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

The neurophysiology of SB appears to be leaning more toward central rather than peripheral factors. There is increasing evidence of the role of the autonomic nervous system, genetics, and comorbidities in the genesis of SB. The scientific literature seems to refute the role of dental occlusion in the causation of bruxing movements. As per the literature, there has been a paradigm shift in the definition and genesis of SB and its possible dental implications and management, which also highlights the need for succinct scientific studies in this regard.

Integrative transcriptome and metabolome analysis of fluoride exposure induced developmental neurotoxicity in mouse brain

Fluoride could cause developmental neurotoxicity and significantly affect the intelligence quotient (IQ) of children. However, the systematic mechanism of neuronal damage caused by excessive fluoride administration in offspring is largely unknown. Here, we present a comprehensive integrative transcriptome and metabolome analysis to study the mechanism of developmental neurotoxicity caused by chronic fluoride exposure. Comparing the different doses of fluoride treatments in two generations revealed the exclusive signature of metabolism pathways and gene expression profiles. In particular, neuronal development and synaptic ion transport are significantly altered at the gene expression and metabolite accumulation levels for both generations, which could act as messengers and enhancers of fluoride-induced systemic neuronal injury. Choline and arachidonic acid metabolism, which highlighted in the integrative analysis, exhibited different regulatory patterns between the two generations, particularly for synaptic vesicle formation and inflammatory factor transport. It may suggest that choline and arachidonic acid metabolism play important roles in developmental neurotoxic responses for offspring mice. Our study provides comprehensive insights into the metabolomic and transcriptomic regulation of fluoride stress responses in the mechanistic explanation of fluoride-induced developmental neurotoxicity.

STXBP1-Related Disorders: Clinical Presentation, Molecular Function, Treatment, and Future Directions

In recent years, the affordability and availability of genetic testing have led to its increased use in clinical care. The increased frequency of testing has led to STXBP1 variants being identified as one of the more common variants associated with neurological disorders. In this review, we aim to summarize the common clinical phenotypes associated with STXBP1 pathogenic variants, provide an overview of their known natural history, and discuss current research into the genotype to phenotype correlation. We will also provide an overview of the suspected normal function of the STXBP1-encoded Munc18-1 protein, animal models, and experimental techniques that have been developed to study its function and use this information to try to explain the diverse phenotypes associated with STXBP1-related disorders. Finally, we will explore current therapies for STXBP1 disorders, including an overview of treatment goals for STXBP1-related disorders, a discussion of the current evidence for therapies, and future directions of personalized medications for STXBP1-related disorders.

HSV-1 latency-associated transcript miR-H3 and miR-H4 target STXBP1 and GABBR2 genes

During latent infection, the HSV-1 virus generates only a single transcript, LAT, which encodes six miRNAs. The GABAergic pathway signaling system is an essential cell signaling pathway influenced by various therapeutic targets and some brain disorders, such as epilepsy. This study found that miRNAs encoding LAT might target the STXBP1 and GABBR2 genes, which are among the significant genes in the GABAergic pathway. Bioinformatic analysis utilizing TargetScan version 5.2 and the RNA22 tools uncovered miRNAs encoding LAT that can influence STXBP1 and GABBR2 transcripts. To evaluate the targeting effect of candidate microRNAs encoding LAT, namely, miR-H3 and miR-H4, LAT constructs were transfected into HEK 293T cells. The expression levels of microRNAs encoding LAT, as well as STXBP1 and GABBR2, were assayed by real-time PCR. Finally, the targeting potential of STXBP1 and GABBR2 3'UTR by LAT-encoded microRNAs was evaluated by the luciferase assay. In the current study, the bioinformatic tool TargetScan demonstrated that miR-H3 has the potential to target the transcripts of the STXBP1 and GABBR2 genes, whereas miR-H4 solely targeted GABBR2. On the other hand, the bioinformatic tool RNA22 validated the potential targeting of STXBP1 and GABBR2 by miR-H3 and miR-H4. Our findings showed that overexpression of miR-H4, miR-H3, or LAT significantly decreased STXBP1 gene expression by an average of 0.0593-fold, 0.237-fold, and 0.84-fold, respectively. Similarly, overexpression of miR-H3 or miR-H4 decreased GABBR2 expression by an average of 0.055- or 0.687-fold, respectively. Notably, targeting the GABBR2 3'UTR with the LAT transcript had no detectable effect. The evaluation of the targeting potential of STXBP1 and GABBR2 3'UTR by microRNAs encoded by LAT was conducted with a luciferase assay. Our results showed that miR-H3 overexpression reduces Renilla expression in psiCHECK2 plasmids with STXBP1 or GABBR2 3'UTR genes by 0.62- and 0.55-fold, respectively. miR-H4 reduced Renilla gene expression regulated by GABBR2's 3'UTR plasmid but had no effect on the Renilla gene expression regulated by STXBP1's 3'UTR. When the LAT transcript was overexpressed, there was a decrease in Renilla expression by 0.44-fold because of the regulation of STXBP1's 3'UTR. However, there was no significant effect observed through the control of GABBR2's 3'UTR.

Natural History and Developmental Trajectories of Individuals With Disease-Causing Variants in STXBP1

BACKGROUND AND OBJECTIVES

Pathogenic variants in STXBP1 are among the major genetic causes of neurodevelopmental disorders. Despite the increasing number of individuals diagnosed without a history of epilepsy, little is known about the natural history and developmental trajectories in this subgroup and endpoints for future therapeutic studies are limited to seizure control.

METHODS

We performed a cross-sectional retrospective study using standardized questionnaires for clinicians and caregivers of individuals with STXBP1-related disorders capturing medical histories, genetic findings, and developmental outcomes. Motor and language function were assessed using Gross Motor Function Classification System (GMFCS) scores and a speech impairment score and were compared within and across clinically defined subgroups.

RESULTS

We collected data of 71 individuals with STXBP1-related disorders, including 44 previously unreported individuals. Median age at inclusion was 5.3 years (interquartile range 3.5-9.3) with the oldest individual aged 43.8 years. Epilepsy was absent in 18/71 (25%) of individuals. The range of developmental outcomes was broad, including 2 individuals presenting with close to age-appropriate motor development. Twenty-nine of 61 individuals (48%) were able to walk unassisted, and 24/69 (35%) were able to speak single words. Individuals without epilepsy presented with a similar onset and spectrum of phenotypic features but had lower GMFCS scores (median 3 vs 4, p < 0.01) than individuals with epilepsy. Individuals with epileptic spasms were less likely to walk unassisted than individuals with other seizure types (6% vs 58%, p < 0.01). Individuals with early epilepsy onset had higher speech impairment scores (p = 0.02) than individuals with later epilepsy onset.

DISCUSSION

We expand the spectrum of STXBP1-related disorders and provide clinical features and developmental trajectories in individuals with and without a history of epilepsy. Individuals with epilepsy, in particular epileptic spasms, and neonatal or early-onset presented with less favorable motor and language functional outcomes compared with individuals without epilepsy. These findings identify children at risk for severe disease and can serve as comparator for future interventional studies in STXBP1-related disorders.

Assessing the landscape of STXBP1-related disorders in 534 individuals

Disease-causing variants in STXBP1 are among the most common genetic causes of neurodevelopmental disorders. However, the phenotypic spectrum in STXBP1-related disorders is wide and clear correlations between variant type and clinical features have not been observed so far. Here, we harmonized clinical data across 534 individuals with STXBP1-related disorders and analysed 19 973 derived phenotypic terms, including phenotypes of 253 individuals previously unreported in the scientific literature. The overall phenotypic landscape in STXBP1-related disorders is characterized by neurodevelopmental abnormalities in 95% and seizures in 89% of individuals, including focal-onset seizures as the most common seizure type (47%). More than 88% of individuals with STXBP1-related disorders have seizure onset in the first year of life, including neonatal seizure onset in 47%. Individuals with protein-truncating variants and deletions in STXBP1 (n = 261) were almost twice as likely to present with West syndrome and were more phenotypically similar than expected by chance. Five genetic hotspots with recurrent variants were identified in more than 10 individuals, including p.Arg406Cys/His (n = 40), p.Arg292Cys/His/Leu/Pro (n = 30), p.Arg551Cys/Gly/His/Leu (n = 24), p.Pro139Leu (n = 12), and p.Arg190Trp (n = 11). None of the recurrent variants were significantly associated with distinct electroclinical syndromes, single phenotypic features, or showed overall clinical similarity, indicating that the baseline variability in STXBP1-related disorders is too high for discrete phenotypic subgroups to emerge. We then reconstructed the seizure history in 62 individuals with STXBP1-related disorders in detail, retrospectively assigning seizure type and seizure frequency monthly across 4433 time intervals, and retrieved 251 anti-seizure medication prescriptions from the electronic medical records. We demonstrate a dynamic pattern of seizure control and complex interplay with response to specific medications particularly in the first year of life when seizures in STXBP1-related disorders are the most prominent. Adrenocorticotropic hormone and phenobarbital were more likely to initially reduce seizure frequency in infantile spasms and focal seizures compared to other treatment options, while the ketogenic diet was most effective in maintaining seizure freedom. In summary, we demonstrate how the multidimensional spectrum of phenotypic features in STXBP1-related disorders can be assessed using a computational phenotype framework to facilitate the development of future precision-medicine approaches.

Clinical whole exome sequencing revealed de novo Heterozygous Stop-Gain and Missense variants in the STXBP1 gene associated with Epilepsy in Saudi Families

Intellectual disability and developmental encephalopathies are mostly linked with infant epilepsy. Epileptic encephalopathy is a term that is used to define association between developmental delay and epilepsy. Mutations in the STXBP1 (Syntaxin-binding protein 1) gene have been previously reported in association with multiple severe early epileptic encephalopathies along with many neurodevelopmental disorders. Among the disorders produced due to any mutations in the STXBP1 gene is developmental and epileptic encephalopathy 4 (OMIM: 612164), is an autosomal dominant neurologic disorder categorized by the onset of tonic seizures in early infancy (usually in the first months of life). In this article, we report two Saudi families one with de novo heterozygous stop-gain mutation c.364C > T and a novel missense c. 305C > A p.Ala102Glu in exon 5 of the STXBP1 gene (OMIM: 602926) lead to development of epileptic encephalopathy 4. The variants identified in the current study broadened the genetic spectrum of STXBP1 gene related with diseases, which will help to add in the literature and benefit to the studies addressing this disease in the future.

Epileptic Phenotypes Associated With SNAREs and Related Synaptic Vesicle Exocytosis Machinery

SNAREs (soluble N-ethylmaleimide sensitive factor attachment protein receptor) are an heterogeneous family of proteins that, together with their key regulators, are implicated in synaptic vesicle exocytosis and synaptic transmission. SNAREs represent the core component of this protein complex. Although the specific mechanisms of the SNARE machinery is still not completely uncovered, studies in recent years have provided a clearer understanding of the interactions regulating the essential fusion machinery for neurotransmitter release. Mutations in genes encoding SNARE proteins or SNARE complex associated proteins have been associated with a variable spectrum of neurological conditions that have been recently defined as “SNAREopathies.” These include neurodevelopmental disorder, autism spectrum disorder (ASD), movement disorders, seizures and epileptiform abnormalities. The SNARE phenotypic spectrum associated with seizures ranges from simple febrile seizures and infantile spasms, to severe early-onset epileptic encephalopathies. Our study aims to review and delineate the epileptic phenotypes associated with dysregulation of synaptic vesicle exocytosis and transmission, focusing on the main proteins of the SNARE core complex (STX1B, VAMP2, SNAP25), tethering complex (STXBP1), and related downstream regulators.

Efficacy of levetiracetam in STXBP1 encephalopathy with different phenotypic and genetic spectra

OBJECTIVE

Syntaxin binding protein 1 (STXBP1) plays an important role in the release of synaptic vesicles. STXBP1-related encephalopathy is a brain dysfunction caused by STXBP1 variation. Levetiracetam (LEV) exerts antiepileptic effects by binding to synaptic vesicle protein 2A (SV2A). This study aimed to analyze the prognosis of LEV treatment of STXBP1 encephalopathy (STXBP1-E) and the correlation among genotype, phenotype, and LEV efficacy.

METHODS

Patients with pathogenic STXBP1 variants were collected from multiple centers, and their clinical history, video electroencephalogram (vEEG) characteristics, imaging examination data, and anti-seizure medication (ASM) history were systematically analyzed. The ASMs related to the prognosis were explored.

RESULTS

Forty patients with STXBP1-E were enrolled in this study. The detailed ASM usage of 37 patients was recorded without intervening in ASM selection. At the endpoint of six months treatment, the results of Fisher's exact test showed that in all ASMs, LEV affected the prognosis of patients with STXBP1-E. LEV was effective in improving the partial remission rate but did not achieve seizure freedom. However, LEV monotherapy could achieve seizure freedom in patients with other early-onset epileptic and encephalopathy. For refractory West syndrome (WS) or Ohtahara syndrome (OS), LEV combined with other ASMs could improve the seizure remission rate.

CONCLUSION

LEV increased the seizure reduction rate and improved the vEEG characteristics in patients with STXBP1-E, but not seizure freedom. LEV combined with other ASMs could increase the seizure reduction rate, especially for refractory WS or OS. Thus, LEV could be considered after identifying the pathogenicity of STXBP1 variants.

Genetic Neonatal-Onset Epilepsies and Developmental/Epileptic Encephalopathies with Movement Disorders: A Systematic Review

Despite expanding next generation sequencing technologies and increasing clinical interest into complex neurologic phenotypes associating epilepsies and developmental/epileptic encephalopathies (DE/EE) with movement disorders (MD), these monogenic conditions have been less extensively investigated in the neonatal period compared to infancy. We reviewed the medical literature in the study period 2000–2020 to report on monogenic conditions characterized by neonatal onset epilepsy and/or DE/EE and development of an MD, and described their electroclinical, genetic and neuroimaging spectra. In accordance with a PRISMA statement, we created a data collection sheet and a protocol specifying inclusion and exclusion criteria. A total of 28 different genes (from 49 papers) leading to neonatal-onset DE/EE with multiple seizure types, mainly featuring tonic and myoclonic, but also focal motor seizures and a hyperkinetic MD in 89% of conditions, with neonatal onset in 22%, were identified. Neonatal seizure semiology, or MD age of onset, were not always available. The rate of hypokinetic MD was low, and was described from the neonatal period only, with WW domain containing oxidoreductase (WWOX) pathogenic variants. The outcome is characterized by high rates of associated neurodevelopmental disorders and microcephaly. Brain MRI findings are either normal or nonspecific in most conditions, but serial imaging can be necessary in order to detect progressive abnormalities. We found high genetic heterogeneity and low numbers of described patients. Neurological phenotypes are complex, reflecting the involvement of genes necessary for early brain development. Future studies should focus on accurate neonatal epileptic phenotyping, and detailed description of semiology and time-course, of the associated MD, especially for the rarest conditions.

Syntaxin Binding Protein 1 Related Epilepsies

Syntaxin binding protein 1 (STXBP1), commonly known as MUNC18–1, is a member of SEC1 family membrane trafficking proteins; their function consists in controlling the soluble N-ethylmaleimide-sensitive factor attachment protein receptors complex assembly, making them essentials regulators of vesicle fusion. The precise function and molecular mechanism through which Munc18–1 contributes to neurotransmitter releasing is not entirely understood, but several evidences suggest its probable role in exocytosis. In 2008, heterozygous de novo mutations in neuronal protein Munc18–1 were first referred as a cause of Ohtahara syndrome development. Currently, a wide examination of the published data proved that 3.1% of patients with severe epilepsy carry a pathogenic de novo mutation including STXBP1 and approximately 10.2% of early onset epileptic encephalopathy is due to an aberrant STXBP1 form codified by the mutated gene. STXBP1 mutations can be associated to a wide clinical heterogeneity. All affected individuals show developmental delay and approximately the 95% of cases have seizures and early onset epileptic encephalopathy, characterized by infantile spasms as the main consistent feature. Burst suppression pattern and hypsarrhythmia are the most frequent EEG anomalies. Other neuronal disorders include Rett syndrome and behavioral and movement disorders. Mild dysmorphic features have been detected in a small number of cases. No genotype–phenotype correlation has been reported. Management of STXBP1 encephalopathy requires a multidisciplinary approach, including epilepsy control and neurological rehabilitation. About 25% of patients are refractory to standard therapy. A single or combined antiepileptic drugs may be required. Several studies described vigabatrin, valproic acid, levetiracetam, topiramate, clobazam, and oxcarbazepine as effective in seizure control. Lamotrigine, zonisamide, and phenobarbital are also commonly used. To date, it remains unclear which therapy is the most effective. Severe morbidity and high mortality are inevitable consequences in some of these patients.

STXBP1 encephalopathies: Clinical spectrum, disease mechanisms, and therapeutic strategies

Mutations in Munc18-1/STXBP1 (syntaxin-binding protein 1) are linked to various severe early epileptic encephalopathies and neurodevelopmental disorders. Heterozygous mutations in the STXBP1 gene include missense, nonsense, frameshift, and splice site mutations, as well as intragenic deletions and duplications and whole-gene deletions. No genotype-phenotype correlation has been identified so far, and patients are treated by anti-epileptic drugs because of the lack of a specific disease-modifying therapy. The molecular disease mechanisms underlying STXBP1-linked disorders are yet to be fully understood, but both haploinsufficiency and dominant-negative mechanisms have been proposed. This review focuses on the current understanding of the phenotypic spectrum of STXBP1-linked disorders, as well as discusses disease mechanisms in the context of the numerous pathways in which STXBP1 functions in the brain. We additionally evaluate the available animal models to study these disorders and highlight potential therapeutic approaches for treating these devastating diseases.

Early-Onset Developmental and Epileptic Encephalopathies of Infancy: An Overview of the Genetic Basis and Clinical Features

Our current knowledge of genetically determined forms of epilepsy has shortened the diagnostic pathway usually experienced by the families of infants diagnosed with early-onset developmental and epileptic encephalopathies. Genetic causes can be found in up to 80% of infants presenting with early-onset developmental and epileptic encephalopathies, often in the context of an uneventful perinatal history and with no clear underlying brain abnormalities. Although current disease-specific therapies remain limited and patient outcomes are often guarded, a genetic diagnosis may lead to early therapeutic intervention using new and/or repurposed therapies. In this review, an overview of epilepsy genetics, the indications for genetic testing in infants, the advantages and limitations of each test, and the challenges and ethical implications of genetic testing are discussed. In addition, the following causative genes associated with early-onset developmental and epileptic encephalopathies are discussed in detail: KCNT1, KCNQ2, KCNA2, SCN2A, SCN8A, STXBP1, CDKL5, PIGA, SPTAN1, and GNAO1. The epilepsy phenotypes, comorbidities, electroencephalgraphic findings, neuroimaging findings, and potential targeted therapies for each gene are reviewed.

A comparison of mRNA and circRNA expression between squamous cell carcinoma and adenocarcinoma of the lungs

Lung squamous cell carcinoma (LUSC) and lung adenocarcinoma (LUAD) are the two major subtypes of non-small-cell lung cancer (NSCLC). This study aimed to compare mRNA and circRNA expression patterns between LUSC and LUAD. Cancer tissues from 8 LUSC patients and 12 LUAD patients were collected to obtain mRNA and circRNA expression profiles. The differentially expressed mRNAs (DEmRNAs) and circRNAs (DE-circRNAs) between LUSC and LUAD were screened. Afterwards, miRNA-DEcircRNA pairs and miRNA-DEmRNA pairs were predicted to construct a competing endogenous RNAs (ceRNAs) network, followed by functional enrichment analysis and survival analysis. In total, 635 DEmRNAs and 245 DEcircRNAs were obtained. The ceRNA analysis revealed that genes, such as EPHA2, EPHA7, NTRK2, CDK6, hsa_circ_027570, hsa_circ_006089, and hsa-circ_035997, had distinct expression patterns between LUSC and LUAD. Also, functional enrichment analysis indicated that DEmRNAs were mainly enriched in ERK1 and ERK2 cascade. Survival analyses suggested that STXBP1 and PMEPA1 were associated the prognosis of with both LUAD and LUSC, whereas EPHA2 and CDK6 might serve as prognostic factors for LUSC and LUAD, respectively. In conclusion, genes such as EPHA2, EPHA7, NTRK2, and CDK6 had different patterns in the two major histological subtypes of NSCLC. Notably, EPHA2 and CDK6 might be considered as potential therapeutic targets for LUSC and LUAD, respectively.

Oral Manifestations of Wolf-Hirschhorn Syndrome: Genotype-Phenotype Correlation Analysis

Background: Wolf-Hirschhorn syndrome (WHS) is a rare disease caused by deletion in the distal moiety of the short arm of chromosome 4. The objectives of this study were to report the most representative oral findings of WHS, relate them with other clinical characteristics of the disease, and establish possible phenotype-genotype correlation. Methods: The study was conducted at 6 reference centers distributed throughout Spain during 2018–2019. The study group consisted of 31 patients with WHS who underwent a standardized oral examination. Due to behavioral reasons, imaging studies were performed on only 11 of the children 6 years of age or older. All participants had previously undergone a specific medical examination for WHS, during which anatomical, functional, epilepsy-related, and genetic variables were recorded. Results: The most prevalent oral manifestations were delayed tooth eruption (74.1%), bruxism (64.5%), dental agenesis (63.6%), micrognathia (60.0%), oligodontia (45.5%), and downturned corners of the mouth (32.3%). We detected strong correlation between psychomotor delay and oligodontia (p = 0.008; Cramér’s V coefficient, 0.75). The size of the deletion was correlated in a statistically significant manner with the presence of oligodontia (p = 0.009; point-biserial correlation coefficient, 0.75). Conclusion: Certain oral manifestations prevalent in WHS can form part of the syndrome’s phenotypic variability. A number of the characteristics of WHS, such as psychomotor delay and epilepsy, are correlated with oral findings such as oligodontia and bruxism. Although most genotype-phenotype correlations are currently unknown, most of them seem to be associated with larger deletions, suggesting that some oral-facial candidate genes might be outside the critical WHS region, indicating that WHS is a contiguous gene syndrome.

Encefalopatía epiléptica infantil en un paciente colombiano con una variante patogénica de novo en el gen STXBP1

El desarrollo de los estudios moleculares ha permitido identificar la etiología genética de diversas enfermedades como   las encefalopatías epilépticas infantiles, las cuales se han asociado con variantes patogénicas en diferentes genes, entre   ellos el STXBP1. La encefalopatía con epilepsia STXBP1 es una enfermedad genética con un patrón de herencia autosómico dominante, donde están alterados los mecanismos reguladores de la liberación de neurotransmisores por parte de las vesículas sinápticas, con alteración del neurodesarrollo. La edad de presentación del trastorno es temprano, con convulsiones en los primeros dos meses de vida. Los pacientes presentan dificultades en la alimentación, trastornos del movimiento y alteración del espectro autista. En este artículo presentamos el caso clínico de un paciente colombiano con encefalopatía epiléptica STXBP1 revisando los aspectos clínicos de la enfermedad, dirigido a profesionales de la salud para sensibilizarlos y así lograr el diagnóstico temprano. Esta es la primera publicación en el país de un paciente con esta etiología.

Molecular Modelling and Dynamics Study of nsSNP in STXBP1 Gene in Early Infantile Epileptic Encephalopathy Disease

Early Infantile Epileptic Encephalopathy (known as Ohtahara Syndrome) is one of the most severe and earliest forms of epilepsy, characterized by early seizures onset. It affects newborns and children between two and six years old. Among the genes that have been associated with early infantile epileptic encephalopathy, the STXBP1 gene, which encodes the Syntaxin binding protein1a that is involved in SNARE complex formation, contributes to synaptic vesicles exocytosis. The aim of this study was to identify the most pathogenic polymorphisms of STXBP1 gene and determine their impact on the structure and stability of Stxbp1 protein. The high-risk nonsynonymous single nucleotide polymorphisms (nsSNPs) in the STXBP1 gene were predicted using 13 bioinformatics tools. The conservation analysis was realized by CONSURF web server. The analysis of the impact of the pathogenic SNPs on the structure of Stxbp1 protein was realized using YASARA software, and the molecular dynamics simulation was performed using GROMACS software. Out of 245 nsSNPs, we identified 11 (S42P, H103D R190W, R235G, D238E, L256P, P335S, C354Y, L365V, R406C, and G544D) as deleterious using in silico prediction tools. Conservation analysis results revealed that all these nsSNPs were located in conserved regions. The comparison of the hydrogen and hydrophobic interactions in the wild type Stxbp1 structure and its mutant forms showed that all these nsSNPs affect the protein structure on different levels. The molecular dynamics simulations revealed that the total of nsSNPs affect the protein stability, residual fluctuation, and the compaction at different levels. This study provides helpful information on high risk nsSNPs that may affect the Stxbp1 protein structure and function. Thus, these variants should be taken into consideration during the genetic screening of patients suffering from early infantile epileptic encephalopathy.

Pathogenic Variants in STXBP1 and in Genes for GABAa Receptor Subunities Cause Atypical Rett/Rett-like Phenotypes

Rett syndrome (RTT) is a neurodevelopmental disorder, affecting 1 in 10,000 girls. Intellectual disability, loss of speech and hand skills with stereotypies, seizures and ataxia are recurrent features. Stringent diagnostic criteria distinguish classical Rett, caused by a MECP2 pathogenic variant in 95% of cases, from atypical girls, 40-73% carrying MECP2 variants, and rarely CDKL5 and FOXG1 alterations. A large fraction of atypical and RTT-like patients remain without genetic cause. Next Generation Sequencing (NGS) targeted to multigene panels/Whole Exome Sequencing (WES) in 137 girls suspected for RTT led to the identification of a de novo variant in STXBP1 gene in four atypical RTT and two RTT-like girls. De novo pathogenic variants-one in GABRB2 and, for first time, one in GABRG2-were disclosed in classic and atypical RTT patients. Interestingly, the GABRG2 variant occurred at low rate percentage in blood and buccal swabs, reinforcing the relevance of mosaicism in neurological disorders. We confirm the role of STXBP1 in atypical RTT/RTT-like patients if early psychomotor delay and epilepsy before 2 years of age are observed, indicating its inclusion in the RTT diagnostic panel. Lastly, we report pathogenic variants in Gamma-aminobutyric acid-A (GABAa) receptors as a cause of atypical/classic RTT phenotype, in accordance with the deregulation of GABAergic pathway observed in MECP2 defective in vitro and in vivo models.