Infantile Epileptic Spasms Syndrome Complicated by Leigh Syndrome and Leigh-Like Syndrome: A Retrospective, Nationwide, Multicenter Case Series.

BACKGROUND: Six percent of patients with Leigh syndrome (LS) present with infantile epileptic spasms syndrome (IESS). However, treatment strategies for IESS with LS remain unclear. This retrospective study aimed to evaluate the efficacy and safety of treatment strategies in patients with IESS complicated by LS and Leigh-like syndrome (LLS). METHODS: We distributed questionnaires to 750 facilities in Japan, and the clinical data of 21 patients from 15 hospitals were collected. The data comprised treatment strategies, including adrenocorticotropic hormone (ACTH) therapy, ketogenic diet (KD) therapy, and antiseizure medications (ASMs); effectiveness of each treatment; and the adverse events. RESULTS: The median age at LS and LLS diagnosis was 7 months (range: 0 to 50), whereas that at the onset of epileptic spasms was 7 (range: 3 to 20). LS was diagnosed in 17 patients and LLS in four patients. Seven, two, five, and seven patients received ACTH + ASMs, ACTH + KD + ASMs, KD + ASMs, and ASMs only, respectively. Four (44%) of nine patients treated with ACTH and one (14%) of seven patients treated with KD achieved electroclinical remission within one month of treatment. No patients treated with only ASMs achieved electroclinical remission. Seven patients (33%) achieved electroclinical remission by the last follow-up. Adverse events were reported in four patients treated with ACTH, none treated with KD therapy, and eight treated with ASMs. CONCLUSION: ACTH therapy shows the best efficacy and rapid action in patients with IESS complicated by LS and LLS. The effectiveness of KD therapy and ASMs in this study was insufficient.

α-Synuclein pathology in Drosophila melanogaster is exacerbated by haploinsufficiency of Rop: connecting STXBP1 encephalopathy with α-synucleinopathies.

Syntaxin-binding protein 1 (STXBP1) is a presynaptic protein that plays important roles in synaptic vesicle docking and fusion. STXBP1 haploinsufficiency causes STXBP1 encephalopathy (STXBP1-E), which encompasses neurological disturbances including epilepsy, neurodevelopmental disorders, and movement disorders. Most patients with STXBP1-E present with regression and movement disorders in adulthood, highlighting the importance of a deeper understanding of the neurodegenerative aspects of STXBP1-E. An in vitro study proposed an interesting new role of STXBP1 as a molecular chaperone for α-Synuclein (αSyn), a key molecule in the pathogenesis of neurodegenerative disorders. However, no studies have shown αSyn pathology in model organisms or patients with STXBP1-E. In this study, we used Drosophila models to examine the effects of STXBP1 haploinsufficiency on αSyn-induced neurotoxicity in vivo. We demonstrated that haploinsufficiency of Ras opposite (Rop), the Drosophila ortholog of STXBP1, exacerbates compound eye degeneration, locomotor dysfunction, and dopaminergic neurodegeneration in αSyn-expressing flies. This phenotypic aggravation was associated with a significant increase in detergent-insoluble αSyn levels in the head. Furthermore, we tested whether trehalose, which has neuroprotective effects in various models of neurodegenerative disorders, mitigates αSyn-induced neurotoxicity exacerbated by Rop haploinsufficiency. In flies expressing αSyn and carrying a heterozygous Rop null variant, trehalose supplementation effectively alleviates neuronal phenotypes, accompanied by a decrease in detergent-insoluble αSyn in the head. In conclusion, this study revealed that Rop haploinsufficiency exacerbates αSyn-induced neurotoxicity by altering the αSyn aggregation propensity. This study not only contributes to understanding the mechanisms of neurodegeneration in STXBP1-E patients, but also provides new insights into the pathogenesis of α-synucleinopathies.

Bilateral choroid plexus resection in a 9p hexasomy/tetrasomy mosaic patient.

Previous reports have shown that a gain of the chromosome 9 short arm (9p) is associated with choroid plexus hyperplasia (CPH). Furthermore, CPH can lead to communicating hydrocephalus; however, no cases of CPH with 9p gain requiring choroid plexus resection have been reported. Here, we describe the first case in which a 9p hexasomy/tetrasomy mosaic patient required choroid plexus resection for hydrocephalus. This finding suggested that the 9p copy number is correlated with CPH severity.

Knockdown of Chronophage in the nervous system mimics features of neurodevelopmental disorders caused by BCL11A/B variants.

Neurodevelopmental disorders (NDD) are a group of disorders that include intellectual disability. Although several genes have been implicated in NDD, the molecular mechanisms underlying its pathogenesis remain unclear. Therefore, it is important to develop novel models to analyze the functions of NDD-causing genes in vivo. Recently, rare pathogenic variants of the B-cell lymphoma/leukemia11A/B (BCL11A/B) gene have been identified in several patients with NDD. Drosophila carries the Chronophage (Cph) gene, which has been predicted to be a homolog of BCL11A/B based on the conservation of the amino acid sequence. In the present study, we investigated whether nervous system-specific knockdown of Cph mimics NDD phenotypes in Drosophila. Nervous system-specific knockdown of Cph induced learning and locomotor defects in larvae and epilepsy-like behaviors in adults. The number of synaptic branches was also elevated in the larval neuromuscular junction without a corresponding increase in the number of boutons. Furthermore, the expression levels of putative target genes that are Drosophila homologs of the mammalian BCL11 target genes were decreased in Cph knockdown flies. These results suggest that Cph knockdown flies are a promising model for investigating the pathology of NDD-induced BCL11A/B dysfunction.

Leigh-like syndrome with progressive cerebellar atrophy caused by novel HIBCH variants.

Pathogenic variants in the HIBCH gene cause HIBCH deficiency, leading to mitochondrial disorders associated with valine metabolism. Patients typically present with symptoms such as developmental regression/delay, encephalopathy, hypotonia and dystonia. Brain magnetic resonance imaging (MRI) shows bilateral lesions in the basal ganglia with/without brainstem involvement. Here, we report a case of a Japanese patient with Leigh-like syndrome caused by novel HIBCH variants. Long-term follow-up MRI revealed progressive cerebellar atrophy, which expands the phenotypic spectrum of HIBCH deficiency.

Myosin Va, a Novel Interaction Partner of STXBP1, Is Required to Transport Syntaxin1A to the Plasma Membrane.

Syntaxin-binding protein 1 (STXBP1, also known as Munc18-1) regulates exocytosis as a chaperone protein of Syntaxin1A. The haploinsufficiency of STXBP1 causes early infantile-onset developmental and epileptic encephalopathy, known as STXBP1 encephalopathy. Previously, we reported impaired cellular localization of Syntaxin1A in induced pluripotent stem cell-derived neurons from an STXBP1 encephalopathy patient harboring a nonsense mutation. However, the molecular mechanism of abnormal Syntaxin1A localization in the haploinsufficiency of STXBP1 remains unknown. This study aimed to identify the novel interacting partner of STXBP1 involved in transporting Syntaxin1A to the plasma membrane. Affinity purification coupled with mass spectrometry analysis identified a motor protein Myosin Va as a potential binding partner of STXBP1. Co-immunoprecipitation analysis of the synaptosomal fraction from the mouse and tag-fused recombinant proteins revealed that the STXBP1 short splice variant (STXBP1S) interacted with Myosin Va in addition to Syntaxin1A. These proteins colocalized at the tip of the growth cone and axons in primary cultured hippocampal neurons. Furthermore, RNAi-mediated gene silencing in Neuro2a cells showed that STXBP1 and Myosin Va were required for membrane trafficking of Syntaxin1A. In conclusion, this study proposes a potential role of STXBP1 in the trafficking of the presynaptic protein Syntaxin1A to the plasma membrane in conjunction with Myosin Va.

Quantitative pretreatment EEG predicts efficacy of ACTH therapy in infantile epileptic spasms syndrome.

OBJECTIVE: This study aimed to determine the correlation between outcomes following adrenocorticotrophic hormone (ACTH) therapy and measurements of relative power spectrum (rPS), weighted phase lag index (wPLI), and graph theoretical analysis on pretreatment electroencephalography (EEG) in infants with non-lesional infantile epileptic spasms syndrome (IESS). METHODS: Twenty-eight patients with non-lesional IESS were enrolled. Outcomes were classified based on seizure recurrence following ACTH therapy: seizure-free (F, n = 21) and seizure-recurrence (R, n = 7) groups. The rPS, wPLI, clustering coefficient, and betweenness centrality were calculated on pretreatment EEG and were statistically analyzed to determine the correlation with outcomes following ACTH therapy. RESULTS: The rPS value was significantly higher in the delta frequency band in group R than in group F (p < 0.001). The wPLI values were significantly higher in the delta, theta, and alpha frequency bands in group R than in group F (p = 0.007, <0.001, and <0.001, respectively). The clustering coefficient in the delta frequency band was significantly lower in group R than in group F (p < 0.001). CONCLUSIONS: Our findings demonstrate the significant differences in power and functional connectivity between outcome groups. SIGNIFICANCE: This study may contribute to an early prediction of ACTH therapy outcomes and thus help in the development of appropriate treatment strategies.

Thyroid hypogenesis is associated with a novel AKT3 germline variant that causes megalencephaly and cortical malformation.

The molecular mechanisms involved in thyroid organogenesis have not been fully elucidated. We report a patient with a de novo germline AKT3 variant, NM_005465.7:c.233A > G, p.(Gln78Arg), who presented with congenital hypothyroidism in addition to typical AKT3-related brain disorders. The report of this patient contributes to delineating the associated yet uncertain endocrine complications of this AKT3 disease-causing variant.

Pleomorphic rhabdomyosarcoma in a young adult harboring a novel germline MSH2 variant.

Most cases of rhabdomyosarcoma (RMS) are sporadic and not associated with the Lynch syndrome (LS) spectrum. We report a young adult patient with RMS and a family history of colorectal cancer. Comprehensive cancer genomic profiling (CGP) of his tumor revealed a likely pathogenic variant of MSH2, NM_000251.3:c.1741delA (p.I581Lfs*9), which was also present in his blood sample. The widespread use of CGP may reveal that RMS can be a rare manifestation of LS.

TUBB3 E410K Syndrome With Childhood-Onset Nonalcoholic Steatohepatitis.

CONTEXT: Nonalcoholic fatty liver disease (NAFLD) is becoming a major issue worldwide, even in children. Multiple parallel hits hypothesis has been suggested as progress of NAFLD, but the mechanism of NAFLD is not completely understood. ß-Tubulin is essential in mitoses, neuronal migration, and axon guidance during neuronal development. Pathogenic variants in the TUBB3 gene were shown to be associated with a wide spectrum of neurological abnormalities, but not accompanied by hepatic complications, such as NAFLD. OBJECTIVE: This work aims to examine the association between TUBB3 mutation and nonalcoholic steatohepatitis (NASH). METHODS: An 11-year-old girl has been followed up as having atypical Möbius syndrome since infancy, as she was born with bilateral ptosis, paralytic strabismus, and facial weakness. At age 7 years, she was diagnosed with TUBB3 E410K syndrome by whole-exome sequencing. At age 10 years, her blood examination revealed elevated liver transaminase levels, which persisted for almost 2 years. She underwent liver biopsy, the results of which were suggestive of NASH. RESULTS: The expression of TUBB3 was absent, but that of tyrosine hydroxylase (TH) was present in the parenchymal nerve fibers of the liver. On the other hand, in comparison with an autopsy case of NASH and a normal control, these showed coexpression of TUBB3 and TH in the liver. CONCLUSION: We report the first case of TUBB3 E410K syndrome accompanied by NASH. This case suggests that the TUBB3 mutation may be associated with the pathogenesis and progression of NASH in humans.

Impaired neuronal activity and differential gene expression in STXBP1 encephalopathy patient iPSC-derived GABAergic neurons.

Syntaxin-binding protein 1 (STXBP1; also called MUNC18-1), encoded by STXBP1, is an essential component of the molecular machinery that controls synaptic vesicle docking and fusion. De novo pathogenic variants of STXBP1 cause a complex set of neurological disturbances, namely STXBP1 encephalopathy (STXBP1-E) that includes epilepsy, neurodevelopmental disorders and neurodegeneration. Several animal studies have suggested the contribution of GABAergic dysfunction in STXBP1-E pathogenesis. However, the pathophysiological changes in GABAergic neurons of these patients are still poorly understood. Here, we exclusively generated GABAergic neurons from STXBP1-E patient-derived induced pluripotent stem cells (iPSCs) by transient expression of the transcription factors ASCL1 and DLX2. We also generated CRISPR/Cas9-edited isogenic iPSC-derived GABAergic (iPSC GABA) neurons as controls. We demonstrated that the reduction in STXBP1 protein levels in patient-derived iPSC GABA neurons was slight (approximately 20%) compared to the control neurons, despite a 50% reduction in STXBP1 mRNA levels. Using a microelectrode array-based assay, we found that patient-derived iPSC GABA neurons exhibited dysfunctional maturation with reduced numbers of spontaneous spikes and bursts. These findings reinforce the idea that GABAergic dysfunction is a crucial contributor to STXBP1-E pathogenesis. Moreover, gene expression analysis revealed specific dysregulation of genes previously implicated in epilepsy, neurodevelopment and neurodegeneration in patient-derived iPSC GABA neurons, namely KCNH1, KCNH5, CNN3, RASGRF1, SEMA3A, SIAH3 and INPP5F. Thus, our study provides new insights for understanding the biological processes underlying the widespread neuropathological features of STXBP1-E.

Phenotypes of SMA patients retaining SMN1 with intragenic mutation.

BACKGROUND: Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by homozygous deletion or intragenic mutation of the SMN1 gene. It is well-known that high copy number of its homologous gene, SMN2, modifies the phenotype of SMN1-deleted patients. However, in the patients with intragenic SMN1 mutation, the relationship between phenotype and SMN2 copy number remains unclear. METHODS: We have analyzed a total of 515 Japanese patients with SMA-like symptoms (delayed developmental milestones, respiratory failures, muscle weakness etc.) from 1996 to 2019. SMN1 and SMN2 copy numbers were determined by quantitative polymerase chain reaction (PCR) method and/or multiplex ligation-dependent probe amplification (MLPA) method. Intragenic SMN1 mutations were identified through DNA and RNA analysis of the fresh blood samples. RESULTS: A total of 241 patients were diagnosed as having SMA. The majority of SMA patients showed complete loss of SMN1 (n = 228, 95%), but some patients retained SMN1 and carried an intragenic mutation in the retaining SMN1 (n = 13, 5%). Ten different mutations were identified in these 13 patients, consisting of missense, nonsense, frameshift and splicing defect-causing mutations. The ten mutations were c.275G > C (p.Trp92Ser), c.819_820insT (p.Thr274Tyrfs*32), c.830A > G (p.Tyr277Cys), c.5C > T (p.Ala2Val), c.826 T > C (p.Tyr276His), c.79C > T (p.Gln27*), c.188C > A (p.Ser63*), c.422 T > C (p.Leu141Pro), c.835-2A > G (exon 7 skipping) and c.835-3C > A (exon 7 skipping). It should be noted here that some patients with milder phenotype carried only a single SMN2 copy (n = 3), while other patients with severe phenotype carried 3 SMN2 copies (n = 4). CONCLUSION: Intragenic mutations in SMN1 may contribute more significantly to clinical severity than SMN2 copy numbers.

Low-grade IVH in preterm infants causes cerebellar damage, motor, and cognitive impairment.

BACKGROUND: Few studies have examined the effect of low-grade intraventricular hemorrhage (IVH) on the white matter in the cerebellum and its association with neurodevelopment. We evaluated cerebellar white matter at term-equivalent age (TEA) in preterm infants with low-grade IVH. Furthermore, we assessed neurodevelopmental outcomes at 3 years of age to examine the influence of low-grade IVH on neurodevelopment. METHODS: Thirteen infants with low-grade IVH and 26 without IVH, born at <30 weeks' postmenstrual age (PMA), were enrolled in this study. Diffusion tensor imaging (DTI) parameters, including fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in the middle and superior cerebellar peduncles (SCP), were measured. Neurodevelopmental outcomes at three years of age were assessed and the correlation between DTI parameters and developmental quotient (DQ) was analyzed. RESULTS: Preterm infants with IVH showed lower FA values (P < 0.01) and higher ADC values (P < 0.05) in the SCP at TEA than the no-IVH group. Lower Postural-Motor and Cognitive-Adaptive DQ at 3 years of age were observed in the IVH compared to the no-IVH group. A significant correlation between the FA values in the SCP at TEA and the Posture-Motor DQ was observed at three years of age (P = 0.043, r = 0.50). CONCLUSIONS: These data suggest that low-grade IVH in preterm infants affects the SCP at TEA and that impaired cerebellar white matter correlates with poor motor development at three years of age.

Complex hereditary spastic paraplegia associated with episodic visual loss caused by ACO2 variants.

Most patients with homozygous or compound heterozygous pathogenic ACO2 variants present with muscular hypotonia features, namely, infantile cerebellar-retinal degeneration. Recently, two studies reported rare familial cases of ACO2 variants presenting as complex hereditary spastic paraplegia (HSP) with broad clinical spectra. Here, we report the case of a 20-year-old Japanese woman with complex HSP caused by compound heterozygous ACO2 variants, revealing a new phenotype of episodic visual loss during febrile illness.

Clinical phenotypes of spinal muscular atrophy patients with hybrid SMN gene.

BACKGROUND: Spinal muscular atrophy (SMA) is a neuromuscular disease caused by homozygous deletion of SMN1 exons 7 and 8. However, exon 8 is retained in some cases, where SMN2 exon 7 recombines with SMN1 exon 8, forming a hybrid SMN gene. It remains unknown how the hybrid SMN gene contribute to the SMA phenotype. METHOD: We analyzed 515 patients with clinical suspicion for SMA. SMN1 exons 7 and 8 deletion was detected by PCR followed by enzyme digestion. Hybrid SMN genes were further analyzed by nucleotide sequencing. SMN2 copy number was determined by real-time PCR. RESULTS: SMN1 exon 7 was deleted in 228 out of 515 patients, and SMN1 exon 8 was also deleted in 204 out of the 228 patients. The remaining 24 patients were judged to carry a hybrid SMN gene. In the patients with SMN1 exon 7 deletion, the frequency of the severe phenotype was significantly lower in the patients with hybrid SMN gene than in the patients without hybrid SMN gene. However, as for the distribution of SMN2 exon 7 copy number among the clinical phenotypes, there was no significant difference between both groups of SMA patients with or without hybrid SMN gene. CONCLUSION: Hybrid SMN genes are not rare in Japanese SMA patients, and it appears to be associated with a less severe phenotype. The phenotype of patients with hybrid SMN gene was determined by the copy number of SMN2 exon 7, as similarly for the patients without hybrid SMN gene.

A novel Drosophila model for neurodevelopmental disorders associated with Shwachman-Diamond syndrome.

Genetic defects in ribosome biogenesis result in a group of diseases called ribosomopathies. Patients with ribosomopathies manifest multiorgan phenotypes, including neurological impairments. A well-characterized ribosomopathy, Shwachman-Diamond syndrome (SDS), is mainly associated with loss-of-function mutations in the causal gene SBDS. Children with SDS have neurodevelopmental disorders; however, the neurological consequences of SBDS dysfunction remain poorly defined. In the present study, we investigated the phenotype of Drosophila melanogaster following knockdown of CG8549, the Drosophila ortholog of human SBDS, to provide evidence for the neurological consequences of reduction in physiological SBDS functions. The pan-neuron-specific knockdown of CG8549 was associated with locomotive disabilities, mechanically induced seizures, hyperactivity, learning impairments, and anatomical defects in presynaptic terminals. These results provide the first evidence of a direct link between a reduction in physiological SBDS function and neurological impairments.

Investigating Developmental and Epileptic Encephalopathy Using Drosophila melanogaster.

Developmental and epileptic encephalopathies (DEEs) are the spectrum of severe epilepsies characterized by early-onset, refractory seizures occurring in the context of developmental regression or plateauing. Early infantile epileptic encephalopathy (EIEE) is one of the earliest forms of DEE, manifesting as frequent epileptic spasms and characteristic electroencephalogram findings in early infancy. In recent years, next-generation sequencing approaches have identified a number of monogenic determinants underlying DEE. In the case of EIEE, 85 genes have been registered in Online Mendelian Inheritance in Man as causative genes. Model organisms are indispensable tools for understanding the in vivo roles of the newly identified causative genes. In this review, we first present an overview of epilepsy and its genetic etiology, especially focusing on EIEE and then briefly summarize epilepsy research using animal and patient-derived induced pluripotent stem cell (iPSC) models. The Drosophila model, which is characterized by easy gene manipulation, a short generation time, low cost and fewer ethical restrictions when designing experiments, is optimal for understanding the genetics of DEE. We therefore highlight studies with Drosophila models for EIEE and discuss the future development of their practical use.

Application of induced pluripotent stem cells in epilepsy.

Epilepsy is among the most common neurological disorders, affecting approximately 50 million people worldwide. Importantly, epilepsy is genetically and etiologically heterogenous, but several epilepsy types exhibit similar clinical presentations. Epilepsy-associated genes are being identified. However, the molecular pathomechanisms remain largely unknown. Approximately one-third of epilepsy is refractory to multiple conventional anti-epileptic drugs (AEDs). Induced pluripotent stem cells (iPSCs) provide an excellent tool to study the pathomechanisms underlying epilepsy and to develop novel treatments. Indeed, disease-specific iPSCs have been established for several genetic epilepsies. In particular, the molecular mechanisms underlying certain developmental and epileptic encephalopathies, such as Dravet syndrome, have been revealed. Modeling epilepsy with iPSCs enables new drug development based on the elucidated pathomechanisms. This can also be used to evaluate conventional AEDs and drug repurposing. Furthermore, transplanting neuronal cells derived from iPSCs into the brain has great potential to treat refractory epilepsies. Recent advances in iPSC technology have enabled the generation of neuronal organoids, or "mini brains." These organoids demonstrate electrophysiological activities similar to those of the brain and have the potential for extensive epilepsy research opportunities. Thus, the application of iPSCs in epilepsy provides insight into novel treatments based on the molecular pathomechanisms of epilepsy. In this review, we comprehensively discuss the studies conducted on iPSCs established for genetic epilepsy or epilepsies without major structural dysmorphic features.

Intrathecal nusinersen treatment after ventriculo-peritoneal shunt placement: A case report focusing on the neurofilament light chain in cerebrospinal fluid.

BACKGROUND: In July 2018, a rare and serious adverse effect (AE), namely, communicating hydrocephalus unrelated to meningitis or bleeding, was reported in relation to five patients treated with nusinersen for spinal muscular atrophy (SMA). Some patients were managed using a ventriculo-peritoneal shunt (VPS) implant and continued to receive nusinersen treatment. However, there is limited information concerning the effectiveness and safety of nusinersen treatment for patients with a VPS. CASE REPORT: A female patient exhibited general hypotonia soon after birth and was diagnosed, using genetic analysis, with spinal muscular atrophy. She required permanent invasive ventilation from 2 months of age. She developed a progressive hydrocephalus and underwent placement of a VPS in infancy. Treatment with nusinersen was initiated when she was 7 years old. The neurofilament light-chain (NfL) concentration in the cerebrospinal fluid (CSF) decreased over time with nusinersen treatment. Twelve months have passed since the start of nusinersen treatment and no AEs have been observed. CONCLUSION: Nusinersen treatment may be effective and safe, even after placement of a VPS. NfL levels in the CSF could be valuable markers of disease activity/treatment response even in advanced stages of SMA.