SKAR links pre-mRNA splicing to mTOR/S6K1-mediated enhanced translation efficiency of spliced mRNAs.

Different protein complexes form on newly spliced mRNA to ensure the accuracy and efficiency of eukaryotic gene expression. For example, the exon junction complex (EJC) plays an important role in mRNA surveillance. The EJC also influences the first, or pioneer round of protein synthesis through a mechanism that is poorly understood. We show that the nutrient-, stress-, and energy-sensing checkpoint kinase, mTOR, contributes to the observed enhanced translation efficiency of spliced over nonspliced mRNAs. We demonstrate that, when activated, S6K1 is recruited to the newly synthesized mRNA by SKAR, which is deposited at the EJC during splicing, and that SKAR and S6K1 increase the translation efficiency of spliced mRNA. Thus, SKAR-mediated recruitment of activated S6K1 to newly processed mRNPs serves as a conduit between mTOR checkpoint signaling and the pioneer round of translation when cells exist in conditions supportive of protein synthesis.

Genetics and genotype-phenotype correlations in early onset epileptic encephalopathy with burst suppression.

OBJECTIVE: We sought to identify genetic causes of early onset epileptic encephalopathies with burst suppression (Ohtahara syndrome and early myoclonic encephalopathy) and evaluate genotype-phenotype correlations. METHODS: We enrolled 33 patients with a referral diagnosis of Ohtahara syndrome or early myoclonic encephalopathy without malformations of cortical development. We performed detailed phenotypic assessment including seizure presentation, electroencephalography, and magnetic resonance imaging. We confirmed burst suppression in 28 of 33 patients. Research-based exome sequencing was performed for patients without a previously identified molecular diagnosis from clinical evaluation or a research-based epilepsy gene panel. RESULTS: In 17 of 28 (61%) patients with confirmed early burst suppression, we identified variants predicted to be pathogenic in KCNQ2 (n = 10), STXBP1 (n = 2), SCN2A (n = 2), PNPO (n = 1), PIGA (n = 1), and SEPSECS (n = 1). In 3 of 5 (60%) patients without confirmed early burst suppression, we identified variants predicted to be pathogenic in STXBP1 (n = 2) and SCN2A (n = 1). The patient with the homozygous PNPO variant had a low cerebrospinal fluid pyridoxal-5-phosphate level. Otherwise, no early laboratory or clinical features distinguished the cases associated with pathogenic variants in specific genes from each other or from those with no prior genetic cause identified. INTERPRETATION: We characterize the genetic landscape of epileptic encephalopathy with burst suppression, without brain malformations, and demonstrate feasibility of genetic diagnosis with clinically available testing in >60% of our cohort, with KCNQ2 implicated in one-third. This electroclinical syndrome is associated with pathogenic variation in SEPSECS. Ann Neurol 2017;81:419-429.

The Stress-Induced Atf3-Gelsolin Cascade Underlies Dendritic Spine Deficits in Neuronal Models of Tuberous Sclerosis Complex.

Hyperactivation of the mechanistic target of rapamycin (mTOR) kinase, as a result of loss-of-function mutations in tuberous sclerosis complex 1 (TSC1) or TSC2 genes, causes protein synthesis dysregulation, increased cell size, and aberrant neuronal connectivity. Dysregulated synthesis of synaptic proteins has been implicated in the pathophysiology of autism spectrum disorder (ASD) associated with TSC and fragile X syndrome. However, cell type-specific translational profiles in these disease models remain to be investigated. Here, we used high-fidelity and unbiased Translating Ribosome Affinity Purification (TRAP) methodology to purify ribosome-associated mRNAs and identified translational alterations in a rat neuronal culture model of TSC. We find that expression of many stress and/or activity-dependent proteins is highly induced while some synaptic proteins are repressed. Importantly, transcripts for the activating transcription factor-3 (Atf3) and mitochondrial uncoupling protein-2 (Ucp2) are highly induced in Tsc2-deficient neurons, as well as in a neuron-specific Tsc1 conditional knock-out mouse model, and show differential responses to the mTOR inhibitor rapamycin. Gelsolin, a known target of Atf3 transcriptional activity, is also upregulated. shRNA-mediated block of Atf3 induction suppresses expression of gelsolin, an actin-severing protein, and rescues spine deficits found in Tsc2-deficient neurons. Together, our data demonstrate that a cell-autonomous program consisting of a stress-induced Atf3-gelsolin cascade affects the change in dendritic spine morphology following mTOR hyperactivation. This previously unidentified molecular cascade could be a therapeutic target for treating mTORopathies. SIGNIFICANCE STATEMENT: Tuberous sclerosis complex (TSC) is a genetic disease associated with epilepsy and autism. Dysregulated protein synthesis has been implicated as a cause of this disease. However, cell type-specific translational profiles that are aberrant in this disease are unknown. Here we show that expression of many stress and/or activity-dependent proteins is highly induced while some synaptic proteins are repressed in neurons missing the Tsc2 gene expression. Identification of genes whose translation is abnormal in TSC may provide insights to previously unidentified therapeutic targets.

Blockade of ActRIIB signaling triggers muscle fatigability and metabolic myopathy.

Myostatin regulates skeletal muscle size via the activin receptor IIB (ActRIIB). However, its effect on muscle energy metabolism and energy-dependent muscle function remains largely unexplored. This question needs to be solved urgently since various therapies for neuromuscular diseases based on blockade of ActRIIB signaling are being developed. Here, we show in mice, that 4-month pharmacological abrogation of ActRIIB signaling by treatment with soluble ActRIIB-Fc triggers extreme muscle fatigability. This is associated with elevated serum lactate levels and a severe metabolic myopathy in the mdx mouse, an animal model of Duchenne muscular dystrophy. Blockade of ActRIIB signaling downregulates porin, a crucial ADP/ATP shuttle between cytosol and mitochondrial matrix leading to a consecutive deficiency of oxidative phosphorylation as measured by in vivo Phosphorus Magnetic Resonance Spectroscopy ((31)P-MRS). Further, ActRIIB blockade reduces muscle capillarization, which further compounds the metabolic stress. We show that ActRIIB regulates key determinants of muscle metabolism, such as Pparß, Pgc1α, and Pdk4 thereby optimizing different components of muscle energy metabolism. In conclusion, ActRIIB signaling endows skeletal muscle with high oxidative capacity and low fatigability. The severe metabolic side effects following ActRIIB blockade caution against deploying this strategy, at least in isolation, for treatment of neuromuscular disorders.

Sturge-Weber syndrome: an overview of history, genetics, clinical manifestations, and management.

First described in the late 1800's, Sturge-Weber syndrome is one of the more common neurocutaneous disorders. In most cases, it is caused by a somatic mosaic variant in the GNAQ gene driving aberrant overgrowth in endothelial cells which leads to capillary-venous malformations. Characteristic findings are unilateral facial port-wine stain, ipsilateral parieto-occipital leptomeningeal angioma with calcifications and atrophy, and ipsilateral glaucoma, though there is significant variability. The predilection for facial skin and brain is likely due to common embryologic progenitors. The risk of brain involvement is increased with a hemifacial, forehead, or medial facial port-wine stain. Neurologic features include epilepsy, stroke-like episodes, transient or permanent hemiparesis and visual field deficit, headaches, and cognitive and behavioral impairment. Magnetic resonance imaging reveals contrast-enhancing leptomeningeal angiomatosis, progressive atrophy, calcifications, and ipsilateral dilated choroid plexus. The treatment of glaucoma typically requires surgery and port-wine stains are treated with laser therapy. Retrospective data from small cohorts show potential benefits of presymptomatic treatment with anti-seizure medications and/or low dose aspirin. Epilepsy surgery can benefit those with a greater degree of hemiparesis and intractable seizures. Low-dose aspirin has proven effective in lowering the frequency and severity of recoverable stroke-like events. Sirolimus has been reported preliminarily to have satisfactory results regarding cognitive function in pediatric patients, but is not a mainstay of treatment to date. Quality of life is often negatively affected by port-wine stain appearance, intractable seizures, headaches, and mood disorders. Future studies are warranted assessing medication and surgery outcomes, quality of life measures, and timing of imaging and treatment initiation.

Tuberous sclerosis complex: Diagnostic features, surveillance, and therapeutic strategies.

Tuberous sclerosis complex (TSC) is a rare neurocutaneous disorder of mTOR pathway dysregulation resulting from pathogenic variants in the TSC1 or TSC2 genes. Expression of this disorder may involve abnormal tissue growth and dysfunction within the brain, kidneys, heart, lungs, eyes, skin, bones, and teeth. Neurological manifestations can include subependymal giant cell astrocytomas (SEGAs), high rates of infantile spasms, drug-resistant epilepsy, developmental delay, cognitive impairment, autism spectrum disorder, and other neurobehavioral manifestations. Here we review the potential clinical manifestations of TSC by system, recommended diagnostic and surveillance testing, genetic testing, currently available therapeutic options, and considerations for education and social support resources given the unique challenges of this multi-system disorder.

Sunflower Syndrome: A Survey of Provider Awareness and Management Preferences.

BACKGROUND: Sunflower syndrome is a rare photosensitive pediatric epilepsy characterized by stereotyped hand-waving in response to bright lights. These stereotyped movements with maintained awareness can be mistaken for a movement disorder. This study assessed neurology providers' diagnostic reasoning, evaluation, and treatment of Sunflower syndrome. METHODS: A 32-question anonymized electronic survey, including a clinical vignette and video of hand-waving in sunlight, was distributed to child neurology providers to assess (1) initial diagnosis and evaluation based on clinical information, (2) updated diagnosis and management after electroencephalography (EEG), and (3) prior experience with Sunflower syndrome. RESULTS: Among 277 viewed surveys, 211 respondents provided information about initial diagnosis and evaluation, 200 about updated diagnosis, 191 about management, and 189 about prior clinical experience. Most providers (135, 64%) suspected seizure, whereas fewer suspected movement disorders (29, 14%) or were unsure of the diagnosis (37, 22%). EEG was recommended by 180 (85%). After EEG, 189 (95%) diagnosed epilepsy, 111 of whom specifically diagnosed Sunflower syndrome. The majority (149, 78%) recommended antiseizure medications (ASMs) and sun avoidance (181, 95%). Only 103 (55%) had managed Sunflower syndrome. Epileptologists and those with prior clinical experience were more likely to suspect a seizure, order an EEG, and offer ASMs than those without prior experience. CONCLUSIONS: Although many providers had not managed Sunflower syndrome, the majority recognized this presentation as concerning for epilepsy. Epilepsy training and prior clinical experience are associated with improved recognition and appropriate treatment. Educational initiatives that increase awareness of Sunflower syndrome may improve patient care.

Impact of the 2021 north american winter storms on children with epilepsy.

Purpose: In February 2021 a series of winter storms caused power outages for nearly 10 million people in the United States, Northern Mexico and Canada. In Texas, the storms caused the worst energy infrastructure failure in state history, leading to shortages of water, food and heat for nearly a week. Impacts on health and well-being from natural disasters are greater in vulnerable populations such as individuals with chronic illnesses, for example due to supply chain disruptions. We aimed to determine the impact of the winter storm on our patient population of children with epilepsy (CWE). Methods: We conducted a survey of families with CWE that are being followed at Dell Children's Medical Center in Austin, Texas. Results: Of the 101 families who completed the survey, 62% were negatively affected by the storm. Twenty-five percent had to refill antiseizure medications during the week of disruptions, and of those needing refills, 68% had difficulties obtaining the medications, leading to nine patients-or 36% of those needing a refill-running out of medications and two emergency room visits because of seizures and lack of medications. Conclusions: Our results demonstrate that close to 10% of all patients included in the survey completely ran out of antiseizure medications, and many more were affected by lack of water, heat, power and food. This infrastructure failure emphasizes the need for adequate disaster preparation for vulnerable populations such as children with epilepsy for the future.

Bone Health Screening Practices Among Neurologists in Patients on Antiepileptic Drugs: A Quality Improvement Project.

BACKGROUND: Pediatric patients with epilepsy are at risk for low vitamin D levels, increasing the risk for bone fractures, yet standardized bone health screening is not part of routine care. METHODS: We surveyed pediatric neurologists (n = 68) at our center regarding screening practices, using an 11-item survey; constructed a bone health treatment algorithm; and developed a training intervention to improve screening rates. RESULTS: The overall survey response rate was 47%. Among respondents, 64% estimated that they screened for bone health less than 25% of the time. Chart review before the intervention demonstrated an overall screening rate of 25.1% (n = 50/199). One year after implementation of a standardized algorithm, the overall screening rates increased to 53.8% (n = 100/186). The frequency of prescribing vitamin D for patients treated with antiepileptic medications increased among general neurologists (preintervention rate 16%, postintervention rate 51%, P < 0.01) as well as among epileptologists (preintervention rate 45%, postintervention rate 57%, P = 0.04). CONCLUSION: In a relatively short follow-up period, there were significant changes in care patterns regarding screening for bone health in pediatric patients with epilepsy. Further implementation measures are underway to increase bone health screening and care in this population.

A novel MECP2 mutation in a boy with neonatal encephalopathy and facial dysmorphism.

Methly-CpG-binding protein 2 (MECP2) mutations cause Rett syndrome in females. Here we report on a male infant with neonatal encephalopathy, myoclonic jerks, and irregular breathing patterns caused by a novel frameshift mutation in the MECP2 gene. In addition he has facial dysmorphisms previously not described in these patients.

Yield of Emergent Neuroimaging in Patients With Sturge-Weber Syndrome Presenting With Acute Neurologic Symptoms.

BACKGROUND/AIMS: Seizures, strokelike episodes, and headaches are common complications in patients with Sturge-Weber syndrome. Based on our experience, we hypothesized that patients with Sturge-Weber syndrome have frequent urgent neuroimaging studies when presenting acutely to the emergency department. In this study, we aimed to determine the incidence of acute imaging studies in this patient population and to evaluate the prevalence of findings such as acute intracranial hemorrhagic or ischemic strokes. METHODS: To determine the frequency and yield of brain imaging, we conducted a retrospective chart analysis in patients with Sturge-Weber syndrome who presented to Boston Children's Hospital with acute neurologic symptoms between 1996 and 2016. RESULTS: We reviewed 136 encounters of patients with Sturge-Weber syndrome. In 73 of 136 encounters (53.7%), patients underwent a total of 89 imaging studies, consisting of 47 head computed tomographies (CTs) and 42 brain magnetic resonance images (MRIs). Twenty-two percent of patients imaged underwent both CT and MRI scanning of the brain. Patients with strokelike episodes or headaches were more likely to be imaged compared to patients presenting with seizures (89.7% and 100% vs 34.4%, respectively). None of the neuroimaging studies showed acute hemorrhagic or ischemic strokes. CONCLUSIONS: Acute neurologic manifestations of Sturge-Weber syndrome frequently lead to urgent neuroimaging. In our cohort, there was no imaging evidence of acute hemorrhagic or ischemic strokes. In addition, emergent imaging in patients presenting with breakthrough seizures did not result in meaningful changes in management.

SKAR is a specific target of S6 kinase 1 in cell growth control.

BACKGROUND: The mammalian target of rapamycin (mTOR) and phosphatidylinositol 3-kinase (PI3K) signaling pathways promote cell growth and cell cycle progression in response to nutritional, energy, and mitogenic cues. In mammalian cells, the ribosomal protein S6 kinases, S6K1 and S6K2, lie downstream of mTOR and PI3K, suggesting that translational control through the phosphorylation of S6 regulates cell growth. Interestingly, genetic experiments predict that a substrate that is specific to S6K1 but not S6K2 regulates cell growth. RESULTS: Here we identify SKAR as a novel and specific binding partner and substrate of S6K1 but not S6K2. We find that serines 383 and 385 of human SKAR are insulin-stimulated and rapamycin-sensitive S6K1 phosphorylation sites. Quantitative mass spectrometry reveals that serine 383/385 phosphorylation is sensitive to RNA interference (RNAi)-mediated S6K1 reduction, but not S6K2 reduction. Furthermore, RNAi-mediated reduction of SKAR decreases cell size. SKAR is nuclear protein with homology to the Aly/REF family of RNA binding proteins, which has been proposed to couple transcription with pre-mRNA splicing and mRNA export. CONCLUSIONS: We have identified a novel and specific target of S6K1, SKAR, which regulates cell growth. The homology of SKAR to the Aly/REF family links S6K1 with mRNA biogenesis in the control of cell growth.

Mechanism-based treatment in tuberous sclerosis complex.

BACKGROUND: Tuberous sclerosis complex (TSC) is a genetic multisystem disorder that affects the brain in almost every patient. It is caused by a mutation in the TSC1 or TSC2 genes, which regulate mammalian target of rapamycin (mTOR), a key player in control of cellular growth and protein synthesis. The most frequent neurological symptoms are seizures, which occur in up to 90% of patients and often are intractable, followed by autism spectrum disorders, intellectual disability, attention deficit-hyperactivity disorder, and sleep problems. Conventional treatment has frequently proven insufficient for neurological and behavioral symptoms, particularly seizure control. This review focuses on the role of TSC/mTOR in neuronal development and network formation and recent mechanism-based treatment approaches. METHODS: We performed a literature review to identify ongoing therapeutic challenges and novel strategies. RESULTS: To achieve a better quality of life for many patients, current therapy approaches are directed at restoring dysregulated mTOR signaling. Studies in animals have provided insight into aberrant neuronal network formation caused by constitutive activation of the mTOR pathway, and initial studies in TSC patients using magnetic resonance diffusion tensor imaging and electroencephalogram support a model of impaired neuronal connectivity in TSC. Rapamycin, an mTOR inhibitor, has been used successfully in Tsc-deficient mice to prevent and treat seizures and behavioral abnormalities. There is recent evidence in humans of improved seizure control with mTOR inhibitors. CONCLUSIONS: Current research provides insight into aberrant neuronal connectivity in TSC and the role of mTOR inhibitors as a promising therapeutic approach.