De novo hotspot variants in CYFIP2 cause early-onset epileptic encephalopathy.

OBJECTIVE: The cytoplasmic fragile X mental retardation 1 interacting proteins 2 (CYFIP2) is a component of the WASP-family verprolin-homologous protein (WAVE) regulatory complex, which is involved in actin dynamics. An obvious association of CYFIP2 variants with human neurological disorders has never been reported. Here, we identified de novo hotspot CYFIP2 variants in neurodevelopmental disorders and explore the possible involvement of the CYFIP2 mutants in the WAVE signaling pathway. METHODS: We performed trio-based whole-exome sequencing (WES) in 210 families and case-only WES in 489 individuals with epileptic encephalopathies. The functional effect of CYFIP2 variants on WAVE signaling was evaluated by computational structural analysis and in vitro transfection experiments. RESULTS: We identified three de novo CYFIP2 variants at the Arg87 residue in 4 unrelated individuals with early-onset epileptic encephalopathy. Structural analysis indicated that the Arg87 residue is buried at an interface between CYFIP2 and WAVE1, and the Arg87 variant may disrupt hydrogen bonding, leading to structural instability and aberrant activation of the WAVE regulatory complex. All mutant CYFIP2 showed comparatively weaker interactions to the VCA domain than wild-type CYFIP2. Immunofluorescence revealed that ectopic speckled accumulation of actin and CYFIP2 was significantly increased in cells transfected with mutant CYFIP2. INTERPRETATION: Our findings suggest that de novo Arg87 variants in CYFIP2 have gain-of-function effects on the WAVE signaling pathway and are associated with severe neurological disorders. Ann Neurol 2018;83:794-806.

Japanese multiple epidermal growth factor 10 (MEGF10) myopathy with novel mutations: A phenotype-genotype correlation.

Mutations in the multiple epidermal growth factor-like domains 10 (MEGF10: NM_032446.2) gene are known to cause early-onset myopathy characterized by areflexia, respiratory distress, and dysphagia (EMARDD: OMIM 614399), and a milder phenotype of minicore myopathy. To date, there have been reports of six families with EMARDD and one with a milder disorder. Cysteine mutations in the extracellular EGF-like domain may be responsible for the milder phenotype, but the relationship is not conclusive because of the few reports of this disorder. We here present two Japanese patients with MEGF10 mutations: one with EMARDD phenotype who had a novel homozygous frameshift mutation, c.131_132del, and the other with the milder phenotype who harbored a compound heterozygous mutation, c.2981-2A > G, and a novel missense mutation, p.Cys810Tyr. This is the first report on East Asian patients with MEGF10 myopathy showing two phenotypes, indicating the genotype-phenotype correlation in MEGF10 myopathy.

GRIN1 mutations cause encephalopathy with infantile-onset epilepsy, and hyperkinetic and stereotyped movement disorders.

OBJECTIVE: Recently, de novo mutations in GRIN1 have been identified in patients with nonsyndromic intellectual disability and epileptic encephalopathy. Whole exome sequencing (WES) analysis of patients with genetically unsolved epileptic encephalopathies identified four patients with GRIN1 mutations, allowing us to investigate the phenotypic spectrum of GRIN1 mutations. METHODS: Eighty-eight patients with unclassified early onset epileptic encephalopathies (EOEEs) with an age of onset <1 year were analyzed by WES. The effect of mutations on N-methyl-D-aspartate (NMDA) receptors was examined by mapping altered amino acids onto three-dimensional models. RESULTS: We identified four de novo missense GRIN1 mutations in 4 of 88 patients with unclassified EOEEs. In these four patients, initial symptoms appeared within 3 months of birth, including hyperkinetic movements in two patients (2/4, 50%), and seizures in two patients (2/4, 50%). Involuntary movements, severe developmental delay, and intellectual disability were recognized in all four patients. In addition, abnormal eye movements resembling oculogyric crises and stereotypic hand movements were observed in two and three patients, respectively. All the four patients exhibited only nonspecific focal and diffuse epileptiform abnormality, and never showed suppression-burst or hypsarrhythmia during infancy. A de novo mosaic mutation (c.1923G>A) with a mutant allele frequency of 16% (in DNA of blood leukocytes) was detected in one patient. Three mutations were located in the transmembrane domain (3/4, 75%), and one in the extracellular loop near transmembrane helix 1. All the mutations were predicted to impair the function of the NMDA receptor. SIGNIFICANCE: Clinical features of de novo GRIN1 mutations include infantile involuntary movements, seizures, and hand stereotypies, suggesting that GRIN1 mutations cause encephalopathy resulting in seizures and movement disorders.

Anti-myelin oligodendrocyte glycoprotein (MOG) antibodies in a Japanese boy with recurrent optic neuritis.

BACKGROUND: Myelin oligodendrocyte glycoprotein (MOG) localizes on the outermost surface of the myelin sheath and oligodendrocytes in the central nervous system (CNS). Autoantibodies against MOG are reportedly found in patients with spectrum of inflammatory demyelinating diseases of the CNS, including acute disseminated encephalomyelitis, multiple sclerosis, and neuromyelitis optica. In addition, recent studies have emphasized an association between anti-MOG antibodies and optic neuritis. PATIENT: We present the first case report of a 7-year-old Japanese boy who was positive for anti-MOG antibodies. He experienced four episodes of unilateral optic neuritis and one seizure event. Magnetic resonance imaging revealed T2-hyperintense lesions in the subcortical white matter and midbrain. Although he fulfilled the diagnostic criteria for multiple sclerosis, recombinant interferon beta did not prevent recurrence. Established cell-based immunoassays revealed that he was positive for anti-MOG antibodies and negative for anti-aquaporin 4 antibodies. CONCLUSIONS: Our case report supports the relationship between anti-MOG antibodies and recurrent optic neuritis. Additional studies are needed to establish the clinical significance of anti-MOG antibodies for diagnosis, treatment, and prognosis.

Utility of real-time three-dimensional echocardiography for Duchenne muscular dystrophy with echocardiographic limitations.

Duchenne muscular dystrophy (DMD) is strongly associated with a unique form of dilated cardiomyopathy. Cardiac complications are the leading cause of death in DMD; thus, longitudinal assessments and early intervention for cardiac dysfunction are necessary to improve prognosis. Two-dimensional echocardiography, which is routinely used for cardiac assessment, has some limitations for quantitative analyses in DMD patients with thoracic deformities and regional wall motion abnormalities in the left ventricle. Recently, real-time three-dimensional echocardiography has emerged as a feasible tool for cardiac assessment in various cardiac diseases. The aim of this study was to examine the utility of this technology in DMD. We evaluated left ventricular ejection fraction (LVEF), a major parameter of left ventricular function, in 17 male DMD patients. LVEF values measured by real-time three-dimensional echocardiography were compared with those determined by two established nuclear cardiology methods: "the first-pass method of radionuclide angiocardiography" and "quantitative electrocardiogram-gated single-photon emission computed tomography". A good correlation was observed for LVEF values, particularly between real-time three-dimensional echocardiography and "the first-pass method of radionuclide angiocardiography" (r=0.90, p<0.05). Thus, real-time three-dimensional echocardiography can provide an accurate measurement of LVEF in DMD patients with echocardiographic limitations.

Self-induced seizures presumably by peri-orbital somatosensory self-stimulation: a report of two cases.

Self-induced seizures by somatosensory stimulation are rare. We describe two epileptic patients with self-induced seizures presumably by peri-orbital somatosensory stimulation. Two infants with severely delayed psychomotor development and poor visual acuity after acute subdural hemorrhage in early infancy had been diagnosed as having West syndrome. They evolutionally became to show serial self-induced seizures preceded by rubbing eye with finger in one case and touching right eyebrow with the back of left hand in the other case. Video-electroencephalography (EEG) monitoring was useful to confirm self-induced seizure by peri-orbital self-stimulation. In patients with serial seizures preceded by peculiar behaviors, we need to consider the possibility of self-induced seizures, even if they have a history of West syndrome and severe psychomotor retardation.

Loss-of-function mutation of collybistin is responsible for X-linked mental retardation associated with epilepsy.

Microarray-based comparative genomic hybridization analysis identified a 737-kb microdeletion of Xq11.1, including the cell division cycle 42 guanine nucleotide exchange factor (GEF)-9 gene (ARHGEF9), encoding collybistin, which has a pivotal role in formation of postsynaptic glycine and γ-aminobutyric acid receptor clusters, in a male patient with severe mental retardation and epilepsy. No overlapping deletion with this was identified in the database of genomic copy number variations. A cohort study of ARHGEF9 nucleotide sequence identified a nonsense mutation in another male patient with severe mental retardation and epilepsy. This mutation affects one of the three transcript variants of ARHGEF9, which was confirmed to be expressed in the brain by reverse transcription-PCR. Although this nonsense mutation was shared with the patient's mother, it was not observed in 100 normal individuals. Both male patients suffered epileptic seizures after 1 year of age. Brain magnetic resonance imaging revealed mild frontal atrophy in the first patient and right frontal polymicrogyria in the second patient. Three previously reported mutations of ARHGEF9 consisted of a missense mutation in a male patient with hyperekplexia and two chromosomal disruptions in two female patients. The common phenotypic effects of all ARHGEF9 mutations were mental retardation and epilepsy. Therefore, ARHGEF9 is likely to be responsible for syndromic X-linked mental retardation associated with epilepsy.

[Effectiveness of topiramate in eleven patients with Dravet syndrome].

Dravet syndrome is a rare, but highly refractory epilepsy syndrome. As conventional drugs are not effective, introduction of new effective drugs in clinical use will benefit patients with this disease. We assessed the effectiveness of topiramate (TPM) as adjunctive therapy in 11 patients with Dravet syndrome. TPM was started at doses ranging from 10 to 50 mg/day (0.57 to 2.0 mg/kg/day), and the dosage was increased gradually up to the maximum dose (9 mg/kg/day) depending on efficacy and tolerability. The frequencies of convulsive seizures (generalized tonic-clonic seizures, unilateral seizures, partial onset generalized tonic-clonic seizures) during two months before starting TPM, two months after starting TPM, and the fifth and sixth months after starting TPM were determined. The mean dose (mean +/- SD) of TPM at the second month was 2.7 +/- 1.5 mg/kg/day (1.0-5.7 mg/kg/day, n= 11), and that at the sixth month was 4.5 +/- 2.2 mg/kg/day (1.0-7.3 mg/kg/day, n=10). Evaluation at the second month revealed that one of 11 patients (9%) became seizure-free, six patients (54%) showed greater than 50% seizure reduction, three patients (27%) showed less than 50% seizure reduction, and one patient (9%) had aggravation of convulsive seizures resulting in discontinuation of TPM at the first month. Evaluation at the sixth month revealed that one of 10 patients (10%) was seizure-free, seven patients (70%) had greater than 50% seizure reduction, two patients (20%) had less than 50% seizure reduction, and no patient (0%) had aggravation. Adverse effects were observed in five patients; dizziness in three patients, sleepiness in three patients, and oligohidrosis in one patient. In the present study, TPM was useful as an adjunctive therapy to reduce the frequency of convulsive seizures in patients with Dravet syndrome. A large-scale efficacy study of TPM for Dravet syndrome is warranted.