A novel PAK1 variant causative of neurodevelopmental disorder with postnatal macrocephaly.

p21-activated kinases (PAKs) are protein serine/threonine kinases stimulated by Rho-family p21 GTPases such as CDC42 and RAC. PAKs have been implicated in several human disorders, with pathogenic variants in PAK3 associated with intellectual disability and several PAK members, especially PAK1 and PAK4, overexpressed in human cancer. Recently, de novo PAK1 variants were reported to be causative of neurodevelopmental disorder (ND) with secondary macrocephaly in three patients. We herein report a fourth patient with ND, epilepsy, and macrocephaly caused by a de novo PAK1 missense variant. Two previously reported missense PAK1 variants functioned as activating alleles by reducing PAK1 homodimerization. To examine the pathogenicity of the identified novel p.Ser110Thr variant, we carried out in silico structural analysis. Our findings suggest that this variant also prevents PAK1 homodimerization, leading to constitutive PAK1 activation.

Tolerability and efficacy of perampanel in children with refractory epilepsy.

AIM: There are few reports on the tolerability and efficacy of perampanel, a new antiepileptic drug with a novel mechanism of action, in children and adolescents. We aimed to describe our experience with perampanel add-on and mono-therapy in children with refractory epilepsy. METHOD: Computerized medical records of children treated with perampanel in the paediatric neurology clinic from December 2012 to October 2015 were reviewed. RESULTS: Twenty-four children treated with perampanel (15 females, 9 males) aged 1 year 6 months to 17 years (mean 10y, standard deviation [SD] 4y 5mo) were identified. Adverse events were more common in children aged 12 years or older (89%) compared to younger children (53%), and were mainly behavioural. Ten (42%) children had 50 per cent or higher seizure reduction, two (8%) children had 33 per cent seizure reduction, and seizures were less severe in one (4%) child. Perampanel was discontinued in 13 (54%) children mostly due to adverse events. The mean duration of follow-up in the remaining 11 children was 8.1 months (SD 5.2) (range 1.3-17mo). INTERPRETATION: Perampanel is associated with a relatively high rate of behavioural adverse events mostly in adolescents with refractory epilepsy.

Neurological results of the modified treatment of epilepsy by stimulation of the vagus nerve.

INTRODUCTION: The vagus nerve stimulation (VNS) is used for treatment of drug-resistant epilepsy but laryngeal side effects are common. We tried to improve VNS by modifying the implantation procedure. The aim was to reduce the rate of side effects that have prevented using VNS to its full capacity. METHODS: We operated on 74 pediatric patients for VNS device implantation using a modified surgical protocol incorporating lower neck incision for electrode placement and 36 patients who were operated by standard technique were used for control group. We retrospectively analyzed reduction in frequency of seizures, reduction in severity of seizures (assessed by the shortened Ictal/post-ictal subscale of the Liverpool Seizure Severity Scale that included falling to the ground, postictal headache and sleepiness, incontinence, tongue biting, and injury during attack). RESULTS: Using the new implantation technique, side effects related directly to VNS therapy occurred in six cases (8.1%) showing statistically sound improvement over the standard implantation technique (p Ë‚ 0.05). To achieve good results, the maximum stimulation (3.5 mA) was used in 24 patients (32.4%), with no laryngeal side effects detected. Twelve patients (16.2%) were seizure-free after the first year of VNS treatment. 74.3% of patients experienced a 50% reduction in seizure frequency and improved ictal or postictal activity. CONCLUSION: To minimize laryngeal complications in implantation surgery for VNS devices, the surgical technique may be modified, and lower neck incision could be used. A low rate of laryngeal side effects allows using the VNS device to its full electrical capacity.

Biallelic SZT2 mutations cause infantile encephalopathy with epilepsy and dysmorphic corpus callosum.

Epileptic encephalopathies are genetically heterogeneous severe disorders in which epileptic activity contributes to neurological deterioration. We studied two unrelated children presenting with a distinctive early-onset epileptic encephalopathy characterized by refractory epilepsy and absent developmental milestones, as well as thick and short corpus callosum and persistent cavum septum pellucidum on brain MRI. Using whole-exome sequencing, we identified biallelic mutations in seizure threshold 2 (SZT2) in both affected children. The causative mutations include a homozygous nonsense mutation and a nonsense mutation together with an exonic splice-site mutation in a compound-heterozygous state. The latter mutation leads to exon skipping and premature termination of translation, as shown by RT-PCR in blood RNA of the affected boy. Thus, all three mutations are predicted to result in nonsense-mediated mRNA decay and/or premature protein truncation and thereby loss of SZT2 function. Although the molecular role of the peroxisomal protein SZT2 in neuronal excitability and brain development remains to be defined, Szt2 has been shown to influence seizure threshold and epileptogenesis in mice, consistent with our findings in humans. We conclude that mutations in SZT2 cause a severe type of autosomal-recessive infantile encephalopathy with intractable seizures and distinct neuroradiological anomalies.

The molecular and phenotypic spectrum of IQSEC2-related epilepsy.

OBJECTIVE: IQSEC2 is an X-linked gene associated with intellectual disability (ID) and epilepsy. Herein we characterize the epilepsy/epileptic encephalopathy of patients with IQSEC2 pathogenic variants. METHODS: Forty-eight patients with IQSEC2 variants were identified worldwide through Medline search. Two patients were recruited from our early onset epileptic encephalopathy cohort and one patient from personal communication. The 18 patients who have epilepsy in addition to ID are the subject of this study. Information regarding the 18 patients was ascertained by questionnaire provided to the treating clinicians. RESULTS: Six affected individuals had an inherited IQSEC2 variant and 12 had a de novo one (male-to-female ratio, 12:6). The pathogenic variant types were as follows: missense (8), nonsense (5), frameshift (1), intragenic duplications (2), translocation (1), and insertion (1). An epileptic encephalopathy was diagnosed in 9 (50%) of 18 patients. Seizure onset ranged from 8 months to 4 years; seizure types included spasms, atonic, myoclonic, tonic, absence, focal seizures, and generalized tonic-clonic (GTC) seizures. The electroclinical syndromes could be defined in five patients: late-onset epileptic spasms (three) and Lennox-Gastaut or Lennox-Gastaut-like syndrome (two). Seizures were pharmacoresistant in all affected individuals with epileptic encephalopathy. The epilepsy in the other nine patients had a variable age at onset from infancy to 18 years; seizure types included GTC and absence seizures in the hereditary cases and GTC and focal seizures in de novo cases. Seizures were responsive to medical treatment in most cases. All 18 patients had moderate to profound intellectual disability. Developmental regression, autistic features, hypotonia, strabismus, and white matter changes on brain magnetic resonance imaging (MRI) were prominent features. SIGNIFICANCE: The phenotypic spectrum of IQSEC2 disorders includes epilepsy and epileptic encephalopathy. Epileptic encephalopathy is a main clinical feature in sporadic cases. IQSEC2 should be evaluated in both male and female patients with an epileptic encephalopathy.

Real-Life Experience With Purified Cannabidiol Treatment for Refractory Epilepsy: A Multicenter Retrospective Study.

BACKGROUND: Drug-resistant epilepsy (DRE) affects the development and quality of life of children and young adults. We analyzed the effectiveness and safety of purified CBD in this population. METHODS: A retrospective analysis of medical records of 139 children and young adults (54.7% female, median age 12.0 years) with DRE treated with purified CBD from 2018 to 2022 at five medical centers in Israel. RESULTS: The most common diagnosis was Lennox-Gastaut syndrome (37.4%) followed by Dravet syndrome (16.5%) and tuberous sclerosis complex (16.5%). Median purified CBD dose was 12.5 mg/kg (range 2.5 to 20.0), and median treatment duration was 9.0 months (range 0.5 to 48.0). Most patients (92.2%) had a reduced seizure frequency following treatment initiation; 41.1% had >50% reduction. Fifty-three patients (38.1%) had positive effects: improved alertness (31.7%), improved speech (10.1%), and achievement of new developmental milestones (2.2%). A multivariate linear model assessing predictive factors for seizure reduction demonstrated that patients previously treated with CBD oils, especially those with >50% seizure reduction on prior treatment, were also more likely to have a reduced seizure frequency while they were treated with purified CBD (P = 0.01, P < 0.0001). Development, diagnosis, age, purified CBD dose (0 to 10 mg/kg/day vs 10 to 20 mg/kg/day), and concomitant treatment with clobazam, valproic acid, or everolimus did not affect seizure reduction by purified CBD. The most common adverse events were irritability (20.9%) and drowsiness (12.9%). CONCLUSION: Purified CBD is well-tolerated and effective in reducing seizure frequency in children and young adults with DRE.

[Neuro-psychiatric comorbidity among children and adolescents who suffer from epilepsy].

Epilepsy is quite a common disorder in the child and adolescent population, and it has been studied for many years. Recently, a better understanding has been achieved regarding the comorbidities in epilepsy, including: major depression, anxiety, learning disabilities, etc.. The comorbidities are extensive and affect many aspects in the life of the patient, and his family members, including: psychological development, learning abilities, independence, etc.. Several mechanisms take part in these comorbidities, starting in the cell and ending with a broadened psychological effect. A better understanding of these mechanisms may assist the physicians in diagnosing their patients and tailoring a wide-approach treatment plan, thereby improving the patient's clinical status and his quality of life (and that of his family). The objective of this article is to describe some of the common comorbidities that are present in epilepsy, and outline the multi-disciplinary approach in treating the epileptic child and his/her family.

Therapeutic drug monitoring of lacosamide among children: is it helpful?

Objective: This study aimed to investigate the efficacy and tolerability of Lacosamide (LCM) in a pediatric population with epilepsy using LCM serum concentration and its correlation to the age of the participants and the dosage of the drug. Methods: Demographic and clinical data were collected from the medical records of children with epilepsy treated with LCM at Shamir Medical Center between February 2019 to September 2021, in whom medication blood levels were measured. Trough serum LCM concentration was measured in the biochemical laboratory using High-Performance Liquid Chromatography (HPLC) and correlated with the administered weight-based medication dosing and clinical report. Results: Forty-two children aged 10.43 ± 5.13 years (range: 1-18) were included in the study. The average daily dose of LCM was 306.62 ± 133.20 mg (range: 100-600). The average number of seizures per day was 3.53 ± 7.25 compared to 0.87 ± 1.40 before and after LCM treatment, respectively. The mean LCM serum concentration was 6.74 ± 3.27 mg/L. No statistically significant association was found between LCM serum levels and the clinical response (p = 0.58), as well as the correlation between LCM dosage and the change in seizure rate (p = 0.30). Our study did not find a correlation between LCM serum concentration and LCM dosage and the gender of the participants: males (n = 17) females (n = 23) (p = 0.31 and p = 0.94, respectively). A positive trend was found between age and LCM serum concentrations (r = 0.26, p = 0.09). Conclusion: Based on the data that has been obtained from our study, it appears that therapeutic drug monitoring for LCM may not be necessary. Nonetheless, further research in this area is needed in the light of the relatively small sample size of the study.

Missed meal boluses and poorer glycemic control impact on neurocognitive function may be associated with white matter integrity in adolescents with type 1 diabetes.

Background: The notion that pediatric type 1 diabetes impacts brain function and structure early in life is of great concern. Neurological manifestations, including neurocognitive and behavioral symptoms, may be present from childhood, initially mild and undetectable in daily life. Despite intensive management and technological therapeutic interventions, most pediatric patients do not achieve glycemic control targets for HbA1c. One of the most common causes of such poor control and frequent transient hyperglycemic episodes may be lifestyle factors, including missed meal boluses. Objective: The aim of this study was to assess the association between specific neurocognitive accomplishments-learning and memory, inhibition ability learning, and verbal and semantic memory-during meals with and without bolusing, correlated to diffusion tensor imaging measurements of major related tracts, and glycemic control in adolescents with type 1 diabetes compared with their healthy siblings of similar age. Study design and methods: This is a case-control study of 12- to 18-year-old patients with type 1 diabetes (N = 17, 8 male patients, diabetes duration of 6.53 ± 4.1 years) and their healthy siblings (N = 13). All were hospitalized for 30 h for continuous glucose monitoring and repeated neurocognitive tests as a function of a missed or appropriate pre-meal bolus. This situation was mimicked by controlled, patient blinded manipulation of lunch pre-meal bolus administration to enable capillary glucose level of <180 mg/dl and to >240 mg/d 2 hours after similar meals, at a similar time. The diabetes team randomly and blindly manipulated post-lunch glucose levels by subcutaneous injection of either rapid-acting insulin or 0.9% NaCl solution before lunch. A specific neurocognitive test battery was performed twice, after each manipulation, and its results were compared, along with additional neurocognitive tasks administered during hospitalization without insulin manipulation. Participants underwent brain imaging, including diffusion tensor imaging and tractography. Results: A significant association was demonstrated between glycemic control and performance in the domains of executive functions, inhibition ability, learning and verbal memory, and semantic memory. Inhibition ability was specifically related to food management. Poorer glycemic control (>8.3%) was associated with a slower reaction time. Conclusion: These findings highlight the potential impairment of brain networks responsible for learning, memory, and controlled reactivity to food in adolescents with type 1 diabetes whose glycemic control is poor.

FIRDA, refractory epilepsy, and SEEG-guided RF: A case report.

OBJECTIVES: We will demonstrate that FIRDA (frontal intermittent rhythmic delta activity)-otherwise related to systemic disorders and encephalopathy-has a role as an epileptic biomarker of deep-seated midline SOZ. Its abolishment following SEEG-guided radiofrequency of such SOZ correlates with clinical improvement suggesting its role as a noninvasive biomarker of otherwise inaccessible SOZs. METHODS: We report the case of AK who was admitted with "psychiatric and gastrointestinal complaints." AK's complaints were further associated with FIRDA during VEEG. His previous refractoriness to AEDs, the clinico-electroencephalographic correlation, MRI showing bilateral hippocampal atrophy (more to the left) and severe memory deficits, prompted us to suggest a left temporo-mesial SOZ, for which SEEG was done. Dual SEEG and scalp electrodes were used primarily for diagnostic purposes but taking into account an option for a therapeutic action by RF ablation. RESULTS: The dual array demonstrated a clear association between left hippocampal high voltage spikes and HFOs on SEEG recordings with FIRDA on concomitant scalp EEG parallel to behavioral changes, as suspected in our preliminary hypothesis. A further RF ablation eliminated the epileptiform activity (Spikes, HFOs, and FIRDA) followed by clinical improvement. SIGNIFICANCE: This is the first report showing the clinical significance of FIRDA associated with behavioral changes as a marker for latent refractory mesial epilepsy. SEEG exploration has the potential to uncover deep sources, which are manifested as FIRDA on scalp EEG. These abnormalities and clinical symptoms can be eliminated by RF ablation.

Children and adolescents with ASD treated with CBD-rich cannabis exhibit significant improvements particularly in social symptoms: an open label study.

In recent years there has been growing interest in the potential benefits of CBD-rich cannabis treatment for children with ASD. Several open label studies and one double-blind placebo-controlled study have reported that CBD-rich cannabis is safe and potentially effective in reducing disruptive behaviors and improving social communication. However, previous studies have mostly based their conclusions on parental reports without the use of standardized clinical assessments. Here, we conducted an open label study to examine the efficacy of 6 months of CBD-rich cannabis treatment in children and adolescents with ASD. Longitudinal changes in social communication abilities and restricted and repetitive behaviors (RRB) were quantified using parent report with the Social Responsiveness Scale and clinical assessment with the Autism Diagnostic Observation Schedule (ADOS). We also quantified changes in adaptive behaviors using the Vineland, and cognitive abilities using an age-appropriate Wechsler test. Eighty-two of the 110 recruited participants completed the 6-month treatment protocol. While some participants did not exhibit any improvement in symptoms, there were overall significant improvements in social communication abilities as quantified by the ADOS, SRS, and Vineland with larger improvements in participants who had more severe initial symptoms. Significant improvements in RRB were noted only with parent-reported SRS scores and there were no significant changes in cognitive scores. These findings suggest that treatment with CBD-rich cannabis can yield improvements, particularly in social communication abilities, which were visible even when using standardized clinical assessments. Additional double-blind placebo-controlled studies utilizing standardized assessments are highly warranted for substantiating these findings.

Medical cannabis for the treatment of comorbid symptoms in children with autism spectrum disorder: An interim analysis of biochemical safety.

Background: Autistic Spectrum Disorder (ASD) is a common neurodevelopmental disorder and no effective treatment for the core symptoms is currently available. The present study is part of a larger clinical trial assessing the effects of cannabis oil on autism co-morbidities. Objectives: The aim of the present study was to assess the safety of a CBD-rich oil treatment in children and adolescents with ASD. Methods: Data from 59 children and young adults (ages 5-25 years) from a single-arm, ongoing, prospective, open-label, one center, phase III study was analyzed. Participants received the Nitzan Spectrum® Oil, with cannabis extracts infused in medium chain triglyceride (MCT) oil with a cannabidiol:THC ratio of 20:1, for 6 months. Blood analysis was performed before treatment initiation, and after 3 months. Complete blood count, glucose, urea, creatinine, electrolytes, liver enzymes (AST, ALT, gamma glutamyl transferase), bilirubin, lipid profile, TSH, FT4, thyroid antibodies, prolactin, and testosterone measurements were performed at baseline, prior to starting treatment and at study midpoint, after 3 months of treatment. Results: 59 children (85% male and 15% female) were followed for 18 ± 8 weeks (mean ±SD). The mean total daily dose was 7.88 ± 4.24 mg/kg body weight. No clinically significant differences were found in any of the analytes between baseline and 3 months follow up. Lactate dehydrogenase was significantly higher before treatment (505.36 ± 95.1 IU/l) as compared to its level after 3 months of treatment (470.55 ± 84.22 IU/L) (p = 0.003). FT4 was significantly higher after 3 months of treatment (15.54 ± 1.9) as compared to its level before treatment (15.07 ± 1.88) (p = 0.03), as was TSH [(2.34 ± 1.17) and (2.05 ± 1.02)] before and after 3 months of treatment, respectively (p = 0.01). However, all these values were within normal range. A comparison of the group with additional medications (n = 14) to those who received solely medical cannabis (n = 45) showed no difference in biochemical analysis, including liver enzymes, which remained stable, except for change in potassium level which was significantly higher in the group that did not receive additional medications (0.04 ± 0.37) compared to the group receiving concomitant drug therapy (-0.2 ± 0.33) (p = 0.04). A comparison of patients who received a high dose of the cannabis oil (upper quartile-16 patients), with those receiving a low dose (lower quartile-14 patients) showed no significant difference between the two groups, except for the mean change of total protein, which was significantly higher among patients receiving high dose of CBD (0.19 ± 2.74) compared to those receiving a low dose of CBD (1.71 ± 2.46 (p = 0.01), and mean change in number of platelets, that was significantly lower among patients who received high dose of CBD (13.46 ± 31.38) as compared to those who received low dose of CBD (29.64 ± 26.2) (p = 0.0007). However, both of these changes lack clinical significance. Conclusion: CBD-rich cannabis oil (CBD: THC 20:1), appears to have a good safety profile. Long-term monitoring with a larger number of participants is warranted.

The prevalence of atypical presentations and comorbidities of benign childhood epilepsy with centrotemporal spikes.

PURPOSE: Benign childhood epilepsy with centrotemporal spikes (BCECTS) is the most common epileptic syndrome in childhood. The outcome is usually excellent, but there are some atypical forms of BCECTS with less favorable outcomes. The aim of this study was to delineate the frequency of these atypical features among patients with BCECTS. METHODS: We conducted a retrospective chart study by retrieving the medical records of all consecutive patients with BCECTS who were evaluated in four pediatric neurology outpatient clinics in Israel between the years 1991 and 2008. KEY FINDINGS: A total of 196 patients with BCECTS were identified (78 female and 118 male; mean age at time of diagnosis 7.64 years, range 1.5-14). The mean duration of follow-up was 4.43 years (range 2-11). Nine patients (4.6%) developed electrical status epilepticus in slow waves sleep (ESES) during follow-up, four (2%) had Landau-Kleffner syndrome, three (1.5%) had BCECTS with frequent refractory seizures, two (1%) had BCECTS with falls at presentation, one (0.5%) had a "classic" atypical variant, and one (0.5%) had oromotor dysfunction. None had rolandic status epilepticus. Sixty-one patients (31%) had attention deficit hyperactivity disorder (ADHD), 43 (21.9%) had specific cognitive deficits, and 23 (11.7%) had behavioral abnormalities, including aggressiveness, anxiety disorders, depression, and pervasive developmental disorder (PDD). SIGNIFICANCE: The prevalence of most atypical forms of BCECTS other than ESES is low. There is, however, a high prevalence of ADHD and specific cognitive deficits among patients with BCECTS.

Early exposure to cow's milk protein is protective against IgE-mediated cow's milk protein allergy.

BACKGROUND: The diversity in the perceived prevalence, recovery, and risk factors for cow's milk allergy (CMA) necessitated a large-scale, population-based prospective study. OBJECTIVE: We sought to determine the prevalence, cross-reactivity with soy allergy, and risk factors for the development of CMA. METHODS: In a prospective study the feeding history of 13,019 infants was obtained by means of telephone interview (95.8%) or questionnaire (4.2%). Infants with probable adverse reactions to milk were examined, skin prick tested, and challenged orally. RESULTS: Ninety-eight percent of the cohort participated in the study. The cumulative incidence for IgE-mediated CMA was 0.5% (66/13,019 patients). The mean age of cow's milk protein (CMP) introduction was significantly different (P < .001) between the healthy infants (61.6 +/- 92.5 days) and those with IgE-mediated CMA (116.1 +/- 64.9 days). Only 0.05% of the infants who were started on regular CMP formula within the first 14 days versus 1.75% who were started on formula between the ages of 105 and 194 days had IgE-mediated CMA (P < .001). The odds ratio was 19.3 (95% CI, 6.0-62.1) for development of IgE-mediated CMA among infants with exposure to CMP at the age of 15 days or more (P < .001). Sixty-four patients with IgE-mediated CMA tolerated soy, and none had a proved allergy to soy. CONCLUSIONS: IgE-mediated CMA is much less common than generally reported. Early exposure to CMP as a supplement to breast-feeding might promote tolerance. Finally, soy is a reasonable feeding alternative in patients with IgE-mediated CMA.

Iron deficiency in children with attention deficit hyperactivity disorder.

BACKGROUND: Several studies have suggested that iron deficiency may be related to the pathophysiology of attention deficit hyperactivity disorder (ADHD) due to the role of iron in the production of dopamine and noradrenaline. OBJECTIVES: To evaluate the status of iron deficiency in ADHD children, using ferritin levels, a reliable measure of iron storage in body tissue, as an iron status marker, and to investigate a possible correlation between ferritin levels and the diagnosis of ADHD. METHODS: The study group included 113 newly referred ADHD children aged 5-15 years (mean age 8.8 +/- 2.7). RESULTS: Ferritin levels were below 20 ng/ml in 67 children (59%) and above 20 ng/ml in 46 (41%). There was a very low inverse statistical correlation between scores on Conners' Rating Scale and ferritin levels, probably without clinical significance. CONCLUSIONS: Our findings suggest that low iron stores may be related to ADHD pathophysiology; therefore, ferritin should be included in the overall evaluation of children with ADHD.

Novel perspectives of super-high dose sulfonylurea and high-dose oral prednisolone in an infant with DEND syndrome due to V64M heterozygote KCNJ11 mutation.

AIMS: To report a novel mutation associated with developmental delay, epilepsy, and neonatal diabetes-DEND Syndrome, responsive to a novel management combination. METHODS: We describe the investigation, treatment, and genetic diagnosis of a newborn diagnosed with DEND syndrome. RESULTS: The patient was found to be de-novo heterozygous for pathogenic KCNJ11 missense variant: c.190G > A, p. (Val64Met), associated with DEND syndrome, responsive to a combination of super high doses of sulfonylurea (SU) and oral high-dose steroids. A single case was reported so far due to this mutation, presenting with severe DEND syndrome, treated by insulin only. His phenotypic description and management during 18 months, demonstrates this mutation is responsive to super-high doses of SU combined with high dose 6 weeks steroids protocol. CONCLUSIONS: We have identified a heterozygous missense mutation as the etiology for severe DEND syndrome in a one-day old neonate, presenting with asymptomatic hyperglycemia, responsive to a novel management combination.

Reduction in seizure burden in a child with a A350V IQSEC2 mutation using heat therapy with a Jacuzzi.

A child with a A350V IQSEC2 missense mutation resulting in drug-resistant epilepsy stops having seizures when he has a fever. We demonstrate that raising the body temperature of the child using a commercial Jacuzzi dramatically reduces his seizures and appears to improve his social behavioral interactions.

ATP6V0A1 encoding the a1-subunit of the V0 domain of vacuolar H+-ATPases is essential for brain development in humans and mice.

Vacuolar H+-ATPases (V-ATPases) transport protons across cellular membranes to acidify various organelles. ATP6V0A1 encodes the a1-subunit of the V0 domain of V-ATPases, which is strongly expressed in neurons. However, its role in brain development is unknown. Here we report four individuals with developmental and epileptic encephalopathy with ATP6V0A1 variants: two individuals with a de novo missense variant (R741Q) and the other two individuals with biallelic variants comprising one almost complete loss-of-function variant and one missense variant (A512P and N534D). Lysosomal acidification is significantly impaired in cell lines expressing three missense ATP6V0A1 mutants. Homozygous mutant mice harboring human R741Q (Atp6v0a1R741Q) and A512P (Atp6v0a1A512P) variants show embryonic lethality and early postnatal mortality, respectively, suggesting that R741Q affects V-ATPase function more severely. Lysosomal dysfunction resulting in cell death, accumulated autophagosomes and lysosomes, reduced mTORC1 signaling and synaptic connectivity, and lowered neurotransmitter contents of synaptic vesicles are observed in the brains of Atp6v0a1A512P/A512P mice. These findings demonstrate the essential roles of ATP6V0A1/Atp6v0a1 in neuronal development in terms of integrity and connectivity of neurons in both humans and mice.

A novel de novo 27 bp duplication of the ARX gene, resulting from postzygotic mosaicism and leading to three severely affected males in two generations.

The Aristaless Related Homeobox (ARX) gene is a Q(50) paired homeobox gene. These genes are important regulators of essential events during vertebrate embryogenesis, including the development of the central and peripheral nervous system. Mutations in ARX have been identified in at least 82 different families and sporadic cases, and are responsible for at least 8 clinically distinct disorders. The recurrent 24 bp duplication (dup) mutation, c.429_452dup(24 bp), is the most frequent ARX mutation, which accounts for 45% of all cases reported to date. Here we report a novel de novo, familial dup mutation of 27 bp, c.430_456dup(27 bp), which involves the same region of the ARX gene in exon 2, as the dup24 bp mutation. The female progenitor of this dup27 bp allele exhibits mosaicism, likely resulting from a postmitotic de novo mutation event early in embryonic development. Three males with the dup27 bp mutation presented with infantile spasms, two of whom died early in life. Their phenotype appeared more severe, when compared to the spectrum of clinical presentations associated with the dup24 bp mutation. We propose that this might be at least partly due to the single, extra alanine residue (A) (21A in dup27 vs. 20A in dup24), which takes polyalanine tract 2 of ARX beyond the maximum, naturally occurring limit of 20A found in the human genome.