A novel CACNA1A variant in a child with early stroke and intractable epilepsy

Stroke and Stroke-Like Episodes: Recurrent Manifestations in GLUT1 Deficiency Syndrome

BACKGROUND

Since the initial description of glucose transporter-1 deficiency syndrome (Glut1-DS) the phenotype of the condition has expanded, even leading to the recognition of atypical manifestations. We report on eight patients with Glut1-DS who experienced at least one episode of acute focal neurological deficits.

METHODS

We conducted a retrospective analysis, collecting clinical, electrophysiological, neuroradiological, and genetic information. We focused in particular on three well-documented cases.

RESULTS

Among 42 patients with Glut1-DS, eight individuals aged between six and 38 years presented with an acute onset of neurological disturbances: dysarthria/aphasia, oral dyskinesia, swallowing difficulties, paresthesia, facial palsy, hemi/monoplegia, vomiting, headache, and behavioral disturbances. When performed, magnetic resonance imaging (MRI) revealed signs of venous congestion and hypoperfusion and electroencephalography showed focal contralateral slowing. Deficits were transient in all patients but one. Four patients (50%) were on a ketogenic diet (KD), and two of these patients had lower than usual ketonemia levels during the episode. In two patients, MRI demonstrated the presence of an ischemic brain lesion.

CONCLUSIONS

In Glut1-DS, stroke-like episodes are a recurrent manifestation, particularly during early adulthood, and they were reported in 19% of the patients in our cohort. Stroke mimics should be considered a key feature of Glut1-DS, as other paroxysmal disorders. It remains to be established whether a KD can prevent the recurrence of episodes and, if so, at what level of ketosis. Further observations are needed to confirm the correlation between Glut1-DS and ischemic stroke.

Loss of Epitranscriptomic Modification N6-Methyladenosine (m6A) Reader YTHDF1 Exacerbates Ischemic Brain Injury in a Sexually Dimorphic Manner

N6-Methyladenosine (m6A) is a neuronal-enriched, reversible post-transcriptional modification that regulates RNA metabolism. The m6A-modified RNAs recruit various m6A-binding proteins that act as readers. Differential m6A methylation patterns are implicated in ischemic brain damage, yet the precise role of m6A readers in propagating post-stroke m6A signaling remains unclear. We presently evaluated the functional significance of the brain-enriched m6A reader YTHDF1, in post-stroke pathophysiology. Focal cerebral ischemia significantly increased YTHDF1 mRNA and protein expression in adult mice of both sexes. YTHDF1-/- male, but not female, mice subjected to transient middle cerebral artery occlusion (MCAO) showed worsened motor function recovery and increased infarction compared to sex-matched YTHDF1+/+ mice. YTHDF1-/- male, but not female, mice subjected to transient MCAO also showed significantly perturbed expression of genes related to inflammation, and increased infiltration of peripheral immune cells into the peri-infarct cortex, compared with sex-matched YTHDF1+/+ mice. Thus, this study demonstrates a sexual dimorphism of YTHDF1 in regulating post-ischemic inflammation and pathophysiology. Hence, post-stroke epitranscriptomic regulation might be sex-dependent.

The genotype-phenotype correlations of the CACNA1A-related neurodevelopmental disorders: a small case series and literature reviews

BACKGROUND

Genotype-phenotype correlations of the CACNA1A-related neurodevelopmental disorders such as global developmental delay (GDD)/intellectual disability (ID), epileptic encephalopathy (EE), and autism spectrum disorder (ASD) are unknown. We aimed to summarize genotype-phenotype correlations and potential treatment for CACNA1A-related neurodevelopmental disorders.

METHODS

Six children diagnosed with CACNA1A-related neurodevelopmental disorders at Xiangya Hospital, Central South University from April 2018 to July 2021 were enrolled. The PubMed database was systematically searched for all reported patients with CACNA1A-related neurodevelopmental disorders until February 2023. Thereafter, we divided patients into several groups for comparison.

RESULTS

Six patients were recruited from our hospital. Three cases presented with epilepsy, five with GDD/ID, five with ataxia, and two with ASD. The variants included p.G701R, p.R279C, p.D1644N, p.Y62C, p.L1422Sfs*8, and p. R1664Q [two gain-of-function (GOF) and four loss-of-function (LOF) variants]. About 187 individuals with GDD/ID harboring 123 variants were found (case series plus data from literature). Of those 123 variants, p.A713T and p.R1664* were recurrent, 37 were LOF, and 7 were GOF. GOF variants were linked with severe-profound GDD/ID while LOF variants were associated with mild-moderate GDD/ID (p = 0.001). The p.A713T variant correlated with severe-profound GDD/ID (p = 0.003). A total of 130 epileptic patients harboring 83 variants were identified. The epileptic manifestations included status epilepticus (n = 64), provoked seizures (n = 49), focal seizures (n = 37), EE (n = 29), absence seizures (n = 26), and myoclonic seizures (n = 10). About 49 (42.20%) patients had controlled seizures while 67 (57.80%) individuals remained with refractory seizures. Status epilepticus correlated with variants located on S4, S5, and S6 (p = 0.000). Among the 83 epilepsy-related variants, 23 were recurrent, 32 were LOF, and 11 were GOF. Status epilepticus was linked with GOF variants (p = 0.000). LOF variants were associated with absence seizures (p = 0.000). Six patients died at an early age (3 months to ≤5 years). We found 18 children with ASD. Thirteen variants including recurrent ones were identified in those 18 cases. GOF changes were more linked to ASD.

CONCLUSION

The p.A713T variant is linked with severe-profound GDD/ID. More than half of CACNA1A-related epilepsy is refractory. The most common epileptic manifestation is status epilepticus, which correlates with variants located on S4, S5, and S6.

Clinical exome sequencing uncovers a high frequency of Mendelian disorders in infants with stroke: A retrospective analysis

Stroke causes significant disability and is a common cause of death worldwide. Previous studies have estimated that 1%-5% of stroke is attributable to monogenic etiologies. We set out to assess the utility of clinical exome sequencing (ES) in the evaluation of stroke. We retrospectively analyzed 124 individuals who received ES at the Baylor Genetics reference lab between 2012 and 2021 who had stroke as a major part of their reported phenotype. Ages ranged from 10 days to 69 years. 8.9% of the cohort received a diagnosis, including 25% of infants less than 1 year old; an additional 10.5% of the cohort received a probable diagnosis. We identified several syndromes that predispose to stroke such as COL4A1-related brain small vessel disease, homocystinuria caused by CBS mutation, POLG-related disorders, TTC19-linked mitochondrial disease, and RNASEH2A associated Aicardi-Goutieres syndrome. We also observed pathogenic variants in NSD1, PKHD1, HRAS, and ATP13A2, which are genes rarely associated with stroke. Although stroke is a complex phenotype with varying pathologies and risk factors, these results show that use of exome sequencing can be highly relevant in stroke, especially for those presenting <1 year of age.

Complex effects on CaV2.1 channel gating caused by a CACNA1A variant associated with a severe neurodevelopmental disorder

P/Q-type Ca²⁺ currents mediated by Ca_V2.1 channels are essential for active neurotransmitter release at neuromuscular junctions and many central synapses. Mutations in CACNA1A, the gene encoding the principal Ca_V2.1 α_1A subunit, cause a broad spectrum of neurological disorders. Typically, gain-of-function (GOF) mutations are associated with migraine and epilepsy while loss-of-function (LOF) mutations are causative for episodic and congenital ataxias. However, a cluster of severe Ca_V2.1 channelopathies have overlapping presentations which suggests that channel dysfunction in these disorders cannot always be defined bimodally as GOF or LOF. In particular, the R1667P mutation causes focal seizures, generalized hypotonia, dysarthria, congenital ataxia and, in one case, cerebral edema leading ultimately to death. Here, we demonstrate that the R1667P mutation causes both channel GOF (hyperpolarizing voltage-dependence of activation, slowed deactivation) and LOF (slowed activation kinetics) when expressed heterologously in tsA-201 cells. We also observed a substantial reduction in Ca²⁺ current density in this heterologous system. These changes in channel gating and availability/expression manifested in diminished Ca²⁺ flux during action potential-like stimuli. However, the integrated Ca²⁺ fluxes were no different when normalized to tail current amplitude measured upon repolarization from the reversal potential. In summary, our findings indicate a complex functional effect of R1667P and support the idea that pathological missense mutations in Ca_V2.1 may not represent exclusively GOF or LOF.

Genotype-phenotype correlation of CACNA1A variants in children with epilepsy

AIM

To explore the genotypes and phenotypes of CACNA1A variants in children with epilepsy.

METHOD

Eighteen children (six males, 12 females) with CACNA1A variants were identified using next-generation sequencing.

RESULTS

There were 14 missense variants, two nonsense variants, one frameshift variant, and one splice site variant. Sixteen variants were de novo. Age at seizure onset ranged from 1 day to 8 years; median age was 8 months. Multiple seizure types were observed, including focal, generalized tonic-clonic, myoclonic, and absence seizures, as well as epileptic spasms and tonic seizures. Focal motor status epilepticus occurred in 10 individuals and generalized motor status epilepticus occurred in two individuals. All 18 children showed developmental delay. Focal motor status epilepticus resulted in cerebral atrophy in five individuals, mainly on the contralateral side. Interictal electroencephalogram showed focal discharges in 12 individuals, whereas five individuals had generalized discharges. Three individuals were seizure-free, whereas 15 still had seizures and five had recurrent status epilepticus at last follow-up.

INTERPRETATION

Most children with epilepsy and CACNA1A variants had early seizure onset and developmental delay. Focal seizure was the most common seizure type. Most patients experienced status epilepticus. Unilateral cerebral atrophy could occur after focal motor status epilepticus. Patients with CACNA1A variants located in the transmembrane region may be at high risk of status epilepticus.

Two Children with Early-Onset Strokes and Intractable Epilepsy, Both with CACNA1A Mutations

Background: Mutations in the CACNA1A gene have been associated phenotypically with Familial Hemiplegic Migraine Type 1, Episodic Ataxia Type 2, Idiopathic Generalized Epilepsy, and Developmental and Epileptic Encephalopathy 42. Only six cases have linked ischemic strokes to mutations in the CACNA1A gene. Summary of Cases: We describe two unrelated patients who were found to have different mutations of the CACNA1A gene, one being a novel mutation, as shown by whole exome sequencing. One presented with seizures at birth and the other with seizures at 17 months old, both eventually exhibiting intractable epilepsy, ischemic stroke, and developmental delays. Results: Whole exome sequencing demonstrated de novo pathogenic mutations in the CACNA1A gene, which both caused similar phenotypes in unrelated patients. Conclusion: Pediatric patients who present with ischemic stroke and a history of seizures should be evaluated for CACNA1A mutations, as prompt recognition can help providers facilitate appropriate medical management.

Clinical and molecular spectrum of P/Q type calcium channel Cav2.1 in epileptic patients

Background

Epilepsy is a neurological disorder characterized by the potential to induce seizure and accompanied by cognitive, psychological, and social consequences. CACNA1A gene is a voltage-gated P/Q-type Cav2.1 channel that is broadly expressed in the central nervous system, and the pathogenic variants within this gene may be associated with the epileptic phenotype. In the present study, we collected clinical and molecular data related to epileptic patients with CACNA1A pathogenic variants and investigated possible meaningful relationship between age at onset, neurodevelopmental disorders, type of seizures, brain imaging abnormalities, genotype, and protein domains.

Results

In our retrospective literature studies, from among 890 articles reviewed, a total of 90 individuals were related to epilepsy phenotype. Our findings showed that about 90 percent of patients have shown the first symptoms in childhood and teenage years and different types of neurodevelopmental disorders, such as intellectual disability, developmental arrest, and behavioral disorders, have been common findings for these patients. Further, a wide range of abnormalities have been observed in their brain imaging, and generalized seizures have been the most type of seizures in these patients. However, our data showed no specific genotype–phenotype correlation in epileptic patients with CACNA1A pathogenic alterations.

Conclusions

Our study focused on epileptic phenotype in patients with CACNA1A pathogenic variants and showed a wide range of clinical and molecular heterogeneity with no specific genotype–phenotype correlation. It seems that incomplete penetrance, de-novo variants, and modifier genes are obstacles in predicting the clinical outcome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-02101-y.

Genetics in Epilepsy

The presence of unprovoked, recurrent seizures, particularly when drug resistant and associated with cognitive and behavioral deficits, warrants investigation for an underlying genetic cause. This article provides an overview of the major classes of genes associated with epilepsy phenotypes divided into functional categories along with the recommended work-up and therapeutic considerations. Gene discovery in epilepsy supports counseling and anticipatory guidance but also opens the door for precision medicine guiding therapy with a focus on those with disease-modifying effects.

A novel CACNA1A variant in a child with early stroke and intractable epilepsy

Background

CACNA1A variants have been described in several disorders that encompass a wide range of neurologic phenotypes, including hemiplegic migraine, ataxia, cognitive delay, and epilepsy. To date, ischemic stroke caused by a CACNA1A variant has only been reported once in the literature.

Methods

We describe a 4‐year‐old female with recurrent ischemic strokes beginning at 6 weeks of age, intractable epilepsy, and significant global developmental delay. Exome sequencing (ES) was completed for her evaluation.

Results

We found a novel de novo, likely pathogenic variant, p.Leu1692Gln in CACNA1A by ES. The substitution affects a leucine residue that is highly conserved in species from fish to primates.

Conclusion

We present the second case of recurrent ischemic strokes in a patient with CACNA1A mutation. Our findings expand the phenotypic heterogeneity related to Ca_v2.1 (P/Q‐type) calcium channel dysfunction and suggest consideration of CACNA1A disorder in evaluation of pediatric strokes.