A machine learning method can predict loss- versus gain-of-function effects of human genetic variants in disease-associated ion channels.

Tuberous sclerosis complex (TSC) is a multisystem disease with prominent neurologic manifestations such as epilepsy, cognitive impairment and autism spectrum disorder. mTOR inhibitors have successfully been used to treat TSC-related manifestations in older children and adults. However, data on their safety and efficacy in infants and young children are scarce. The objective of this study is to assess the utility and safety of mTOR inhibitor treatment in TSC patients under the age of 2 years. A total of 17 children (median age at study inclusion 2.4 years, range 0–6; 12 males, 5 females) with TSC who received early mTOR inhibitor therapy were studied. mTOR inhibitor treatment was started at a median age of 5 months (range 0–19 months). Reasons for initiation of treatment were cardiac rhabdomyomas (6 cases), subependymal giant cell astrocytomas (SEGA, 5 cases), combination of cardiac rhabdomyomas and SEGA (1 case), refractory epilepsy (4 cases) and disabling congenital focal lymphedema (1 case). In all cases everolimus was used. Everolimus therapy was overall well tolerated. Adverse events were classified according to the Common Terminology Criteria of Adverse Events (CTCAE, Version 5.0). Grade 1–2 adverse events occurred in 12 patients and included mild transient stomatitis (2 cases), worsening of infantile acne (1 case), increases of serum cholesterol and triglycerides (4 cases), changes in serum phosphate levels (2 cases), increase of cholinesterase (2 cases), transient neutropenia (2 cases), transient anemia (1 case), transient lymphopenia (1 case) and recurrent infections (7 cases). No grade 3–4 adverse events were reported. Treatment is currently continued in 13/17 patients. Benefits were reported in 14/17 patients and included decrease of cardiac rhabdomyoma size and improvement of arrhythmia, decrease of SEGA size, reduction of seizure frequency and regression of congenital focal lymphedema. Despite everolimus therapy, two patients treated for intractable epilepsy are still experiencing seizures and another one treated for SEGA showed no volume reduction. This retrospective multicenter study demonstrates that mTOR inhibitor treatment with everolimus is safe in TSC patients under the age of 2 years and shows beneficial effects on cardiac manifestations, SEGA size and early epilepsy.

De novo in-frame deletions and duplications in the SPTAN1 gene, encoding the non-erythrocyte αII spectrin, have been associated with severe West syndrome with hypomyelination and pontocerebellar atrophy. We aimed at comprehensively delineating the phenotypic spectrum associated with SPTAN1 mutations. Using different molecular genetic techniques, we identified 20 patients with a pathogenic or likely pathogenic SPTAN1 variant and reviewed their clinical, genetic and imaging data. SPTAN1 de novo alterations included seven unique missense variants and nine in-frame deletions/duplications of which 12 were novel. The recurrent three-amino acid duplication p.(Asp2303_Leu2305dup) occurred in five patients. Our patient cohort exhibited a broad spectrum of neurodevelopmental phenotypes, comprising six patients with mild to moderate intellectual disability, with or without epilepsy and behavioural disorders, and 14 patients with infantile epileptic encephalopathy, of which 13 had severe neurodevelopmental impairment and four died in early childhood. Imaging studies suggested that the severity of neurological impairment and epilepsy correlates with that of structural abnormalities as well as the mutation type and location. Out of seven patients harbouring mutations outside the α/β spectrin heterodimerization domain, four had normal brain imaging and three exhibited moderately progressive brain and/or cerebellar atrophy. Twelve of 13 patients with mutations located within the spectrin heterodimer contact site exhibited severe and progressive brain, brainstem and cerebellar atrophy, with hypomyelination in most. We used fibroblasts from five patients to study spectrin aggregate formation by Triton-X extraction and immunocytochemistry followed by fluorescence microscopy. αII/βII aggregates and αII spectrin in the insoluble protein fraction were observed in fibroblasts derived from patients with the mutations p.(Glu2207del), p.(Asp2303_Leu2305dup) and p.(Arg2308_Met2309dup), all falling in the nucleation site of the α/β spectrin heterodimer region. Molecular modelling of the seven SPTAN1 amino acid changes provided preliminary evidence for structural alterations of the A-, B- and/or C-helices within each of the mutated spectrin repeats. We conclude that SPTAN1-related disorders comprise a wide spectrum of neurodevelopmental phenotypes ranging from mild to severe and progressive. Spectrin aggregate formation in fibroblasts with mutations in the α/β heterodimerization domain seems to be associated with a severe neurodegenerative course and suggests that the amino acid stretch from Asp2303 to Met2309 in the α20 repeat is important for α/β spectrin heterodimer formation and/or αII spectrin function.

Objective: Cannabidiol (CBD) is approved for treatment of Dravet syndrome (DS), Lennox‐Gastaut syndrome (LGS), and tuberous sclerosis complex (TSC). Several studies suggest antiseizure effects also beyond these three epilepsy syndromes.Methods: In a retrospective multicenter study, we analyzed the efficacy and tolerability of CBD in patients with epilepsy at 16 epilepsy centers.Results: The study cohort comprised 311 patients with epilepsy with a median age of 11.3 (0‐72) years (235 children and adolescents, 76 adults). Therapy with CBD was off‐label in 91.3% of cases due to age, epilepsy subtype, lack of adjunct therapy with clobazam, and/or higher dose applied. CBD titration regimens were slower than recommended, with good tolerability of higher doses particularly in children. Of all patients, 36.9% experienced a reduction in seizure frequency of >50%, independent of their epilepsy subtype or clobazam co‐medication. The median observation period was 15.8 months. About one third of all patients discontinued therapy within the observation period due to adverse effects or lack of efficacy. Adverse effects were reported frequently (46.9%).Significance: Our study highlights that CBD has an antiseizure effect comparable to other antiseizure medications with a positive safety profile independent of the epilepsy subtype. Comedication with clobazam was not associated with a better outcome. Higher doses to achieve seizure frequency reduction were safe, particularly in children. These findings call for further trials for an extended approval of CBD for other epilepsy subtypes and for children <2 years of age.

Pathogenic missense variants in GRIN2A and GRIN2B may result in gain or loss of function (GoF/LoF) of the N-methyl-D-aspartate receptor (NMDAR). This observation gave rise to the hypothesis of successfully treating GRIN-related disorders due to LoF variants with co-agonists of the NMDAR. In this respect, we describe a retrospectively collected series of ten individuals with GRIN2A- or GRIN2B-related disorders who were treated with L-serine, each within an independent n-of-1 trial. Our cohort comprises one individual with a LoF missense variant with clinical improvements confirming the above hypothesis and replicating a previous n-of-1 trial. A second individual with a GoF missense variant was erroneously treated with L-serine and experienced immediate temporary behavioral deterioration further supporting the supposed functional pathomechanism. Eight additional individuals with null variants (that had been interpreted as loss-of-function variants despite not being missense) again showed clinical improvements. Among all nine individuals with LoF missense or null variants, L-serine treatment was associated with improvements in behavior in eight (89%), in development in four (44%), and/or in EEG or seizure frequency in four (44%). None of these nine individuals experienced side effects or adverse findings in the context of L-serine treatment. In summary, we describe the first evidence that L-serine treatment may not only be associated with clinical improvements in GRIN-related disorders due to LoF missense but particularly also null variants.

Pathogenic variants in KCNA2, encoding for the voltage-gated potassium channel K_v1.2, have been identified as the cause for an evolving spectrum of neurological disorders. Affected individuals show early-onset developmental and epileptic encephalopathy, intellectual disability, and movement disorders resulting from cerebellar dysfunction. In addition, individuals with a milder course of epilepsy, complicated hereditary spastic paraplegia, and episodic ataxia have been reported. By analyzing phenotypic, functional, and genetic data from published reports and novel cases, we refine and further delineate phenotypic as well as functional subgroups of KCNA2-associated disorders. Carriers of variants, leading to complex and mixed channel dysfunction that are associated with a gain- and loss-of-potassium conductance, more often show early developmental abnormalities and an earlier onset of epilepsy compared to individuals with variants resulting in loss- or gain-of-function. We describe seven additional individuals harboring three known and the novel KCNA2 variants p.(Pro407Ala) and p.(Tyr417Cys). The location of variants reported here highlights the importance of the proline(405)–valine(406)–proline(407) (PVP) motif in transmembrane domain S6 as a mutational hotspot. A novel case of self-limited infantile seizures suggests a continuous clinical spectrum of KCNA2-related disorders. Our study provides further insights into the clinical spectrum, genotype–phenotype correlation, variability, and predicted functional impact of KCNA2 variants.