[Show abstract][Hide abstract] ABSTRACT: Neuronal migration disorders are human (or animal) diseases that result from a disruption in the normal movement of neurons from their original birth site to their final destination during early development. As a consequence, the neurons remain somewhere along their migratory route, their location depending on the pathological mechanism and its severity. The neurons form characteristic abnormalities, which are morphologically classified into several types, such as lissencephaly, heterotopia, and cobblestone dysplasia. Polymicrogyria is classified as a group of malformations that appear secondary to post-migration development; however, recent findings of the underlying molecular mechanisms reveal overlapping processes in the neuronal migration and post-migration development stages. Mutations of many genes are involved in neuronal migration disorders, such as LIS1 and DCX in classical lissencephaly spectrum, TUBA1A in microlissencephaly with agenesis of the corpus callosum, and RELN and VLDLR in lissencephaly with cerebellar hypoplasia. ARX is of particular interest from basic and clinical perspectives because it is critically involved in tangential migration of GABAergic interneurons in the forebrain and its mutations cause a variety of phenotypes ranging from hydranencephaly or lissencephaly to early-onset epileptic encephalopathies, including Ohtahara syndrome and infantile spasms or intellectual disability with no brain malformations. The recent advances in gene and genome analysis technologies will enable the genetic basis of neuronal migration disorders to be unraveled, which, in turn, will facilitate genotype-phenotype correlations to be determined.
Frontiers in Neuroscience 05/2015; 9:181. DOI:10.3389/fnins.2015.00181 · 3.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.ResultsWe 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.SignificanceClinical 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.
[Show abstract][Hide abstract] ABSTRACT: Whole-exome sequencing (WES) is a useful method to identify disease-causing mutations, however, often no candidate mutations are identified using commonly available targeted probe sets. In a recent analysis, we also could not find candidate mutations for 20.9% (9/43) of our pedigrees with congenital neurological disorder using pre-designed capture probes (SureSelect V4 or V5). One possible cause for this lack of candidates is that standard WES cannot sequence all protein-coding sequences (CDS) due to capture probe design and regions of low coverage, which account for approximately 10% of all CDS regions. In this study, we combined a selective circularization-based target enrichment method (HaloPlex) with a hybrid capture method (SureSelect V5; WES), and achieved a more complete coverage of CDS regions (~97% of all CDS). We applied this approach to 7 (SureSelect V5) out of 9 pedigrees with no candidates through standard WES analysis and identified novel pathogenic mutations in one pedigree. The application of this effective combination of targeted enrichment methodologies can be expected to aid in the identification of novel pathogenic mutations previously missed by standard WES analysis.
[Show abstract][Hide abstract] ABSTRACT: Chromosome 1p32-p31 deletion syndrome involving the Nuclear factor I/A (NFIA) gene is characterized by corpus callosum hypoplasia or defects and urinary tract defects. Herein we report on a case resembling the 1p32-p31 deletion syndrome carrying a de novo truncating mutation (c.1094delC; p.Pro365Hisfs*32) in the NFIA gene, confirming that haploinsufficiency of the NFIA gene is a major determinant of this syndrome. Chromosome 1p32-p31 deletion syndrome (OMIM #613735) involving the Nuclear factor I/A (NFIA) gene is characterized by corpus callosum hypoplasia or defects, hydrocephalus or ven-tricular enlargement and urinary tract defects. 1 Only six cases of this contiguous gene-deletion syndrome have been reported in the literature. 1–5 Additionally, Lu et al. 1 reported two patients showing a similar phenotype, but with balanced translocations breakpoints in the NFIA gene. 6 These authors also demonstrated ventricular enlargement, callosal agenesis and urinary tract defects in homozygous Nfia − / − mice and heterozygous Nfia +/ − mice.
[Show abstract][Hide abstract] ABSTRACT: Recent progress in genetic analysis reveals that a significant proportion of cryptogenic epileptic encephalopathies are single-gene disorders. Mutations in numerous genes for early-onset epileptic encephalopathies have been rapidly identified, including in SPTAN1, which encodes α-II spectrin. The aim of this review is to delineate SPTAN1 encephalopathy as a distinct clinical syndrome. To date, a total of seven epileptic patients with four different in-frame SPTAN1 mutations have been identified. The major clinical features of SPTAN1 mutations include epileptic encephalopathy with hypsarrhythmia, no visual attention, acquired microcephaly, spastic quadriplegia and severe intellectual disability. Brainstem and cerebellar atrophy and cerebral hypomyelination, as observed by magnetic resonance imaging, are specific hallmarks of this condition. A milder variant is characterized by generalized epilepsy with pontocerebellar atrophy. Only in-frame SPTAN1 mutations in the last two spectrin repeats in the C-terminal region lead to dominant negative effects and these specific phenotypes. The last two spectrin repeats are required for α/β spectrin heterodimer associations and the mutations can alter heterodimer formation between the two spectrins. From these data we suggest that SPTAN1 encephalopathy is a distinct clinical syndrome owing to specific SPTAN1 mutations. It is important that this syndrome is recognized by pediatric neurologists to enable proper diagnostic work-up for patients.Journal of Human Genetics advance online publication, 29 January 2015; doi:10.1038/jhg.2015.5.
Journal of Human Genetics 01/2015; 60(4). DOI:10.1038/jhg.2015.5 · 2.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Megalencephaly capillary malformation (MCAP) is a syndrome involving brain overgrowth, characterized by megalencephaly, capillary malformations, asymmetric growth, polymicrogyria, polydactyly, and syndactyly. Cerebellar tonsillar herniation (CTH) and ventriculomegaly are also observed in over half the patients with this syndrome. Early sudden death has been reported in MCAP, but its causes and the surgical strategies for its prevention remain unclear.
Here, we report on a patient with MCAP who died suddenly at 5 months of age. He presented with progressive macrocephaly and hypotonia. MRI performed at 4 months of age showed tight posterior fossa, bilateral perisylvian polymicrogyria, enlargement of the straight sinus, and a thickened corpus callosum. However, since the patient did not exhibit capillary malformation, polydactyly, or syndactyly, a definitive diagnosis of MCAP could not be made. He died suddenly while asleep at home 1 month later. The sudden death of MCAP patients was previously attributed to CTH, convulsion, or arrhythmia. In this case, progressive cerebellar enlargement appeared to be the underlying cause. After the patient's death, using his preserved DNA, a missense mutation in the AKT3 gene was identified. Vakt murine thymoma viral oncogene homologue (AKT) is a serine-threonine kinase that functions in the mammalian target of rapamycin (mTOR) pathway and plays an important role in cell proliferation.
Accurate early diagnosis, including imaging and genetic analyses, and the recognition and treatment of critical conditions are required to prevent the sudden death of patients with MCAP.
Child s Nervous System 11/2014; DOI:10.1007/s00381-014-2589-y · 1.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sturge-Weber syndrome (SWS) is a neurocutaneous disorder characterized by capillary malformation (port-wine stains), and choroidal and leptomeningeal vascular malformations. Previously, the recurrent somatic mutation c.548G>A (p.R183Q) in the G-α q gene (GNAQ) was identified as causative in SWS and non-syndromic port-wine stain patients using whole-genome sequencing. In this study, we investigated somatic mutations in GNAQ by next-generation sequencing. We first performed targeted amplicon sequencing of 15 blood-brain-paired samples in sporadic SWS and identified the recurrent somatic c.548G>A mutation in 80% of patients (12 of 15). The percentage of mutant alleles in brain tissues of these 12 patients ranged from 3.6 to 8.9%. We found no other somatic mutations in any of the seven GNAQ exons in the remaining three patients without c.548G>A. These findings suggest that the recurrent somatic GNAQ mutation c.548G>A is the major determinant genetic factor for SWS and imply that other mutated candidate gene(s) may exist in SWS.Journal of Human Genetics advance online publication, 6 November 2014; doi:10.1038/jhg.2014.95.
Journal of Human Genetics 11/2014; 59(12). DOI:10.1038/jhg.2014.95 · 2.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Kinesins are a large superfamily of molecular motors. They move along microtubule filaments and are powered by the hydrolysis of ATP. This transport system is essential for neuronal function and survival. KIF1A belongs to the kinesin 3 family and involves in the anterograde transport of synaptic vesicle precursors along axons. Several studies confirmed that KIF1A mutations cause spastic paraplegia and sensory neuropathy in an autosomal-recessive fashion. A missense mutation in the KIF1A gene (p.Thr99Met) has been reported in a patient with intellectual disability (ID), axial hypotonia and peripheral spasticity. Mild atrophy of the cerebellar vermis was found on magnetic resonance imaging. The mutation was heterozygous and de novo. We identified the second patient with the p.T99M mutation in the KIF1A gene by whole-exome sequencing. He showed severe ID, spasticity, optic atrophy, neurogenic bladder, growth failure and progressive cerebellar atrophy. The p.T99M mutation may be a common recurrent mutation. We suppose that this specific mutation of KIF1A shows a novel neurodegenerative syndrome.Journal of Human Genetics advance online publication, 25 September 2014; doi:10.1038/jhg.2014.80.
Journal of Human Genetics 09/2014; DOI:10.1038/jhg.2014.80 · 2.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Recently, de novo mutations in TBL1XR1 were found in two patients with autism spectrum disorders. Here, we report on a Japanese girl presenting with West syndrome, Rett syndrome-like and autistic features. Her initial development was normal until she developed a series of spasms at 5 months of age. Electroencephalogram at 7 months showed a pattern of hypsarrhythmia, which led to a diagnosis of West syndrome. Stereotypic hand movements appeared at 8 months of age, and autistic features such as deficits in communication, hyperactivity and excitability were observed later, at 4 years and 9 months. Whole exome sequencing of the patient and her parents revealed a de novo TBL1XR1 mutation [c.209 G>A (p.Gly70Asp)] occurring at an evolutionarily conserved amino acid in an F-box-like domain. Our report expands the clinical spectrum of TBL1XR1 mutations to West syndrome with Rett-like features, together with autistic features.Journal of Human Genetics advance online publication, 7 August 2014; doi:10.1038/jhg.2014.71.
Journal of Human Genetics 08/2014; 59(10). DOI:10.1038/jhg.2014.71 · 2.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We developed a next-generation sequencing(NGS)based mutation screening strategy for neurodevelopmental diseases. Using this system, we screened 284 genes in 40 patients. Several novel mutations were discovered. Patient 1 had a novel mutation in ACTB. Her dysmorphic feature was mild for Baraitser-Winter syndrome. Patient 2 had a truncating mutation of DYRK1A. She lacked microcephaly, which was previously assumed to be a constant feature of DYRK1A loss of function. Patient 3 had a novel mutation in GABRD gene. She showed Rett syndrome like features. Patient 4 was diagnosed with Noonan syndrome with PTPN11 mutation. He showed complete agenesis of corpus callosum. We discussed these novel findings.
[Show abstract][Hide abstract] ABSTRACT: Background:
Adrenocorticotropic hormone (ACTH) therapy is the first-line therapy for infantile spasms, and is effective for many other intractable epilepsies. While spasms may respond to ACTH for weeks, a substantial proportion of patients develop recurrent seizures over a yearly period. To maintain efficacy, we treated two children with intractable epilepsy with weekly ACTH therapy for 1 year and described the changes in clinical seizures, electroencephalograms, developmental assessments and side effects.
Subjects and methods:
A girl with infantile spasms due to lissencephaly and a boy with atypical absence seizures were studied. In both cases, seizures were frequent and resistant to antiepileptic drugs; electroencephalograms showed continuous epileptiform activities, and the patients' development was delayed and stagnant prior to ACTH treatment. The initial ACTH therapy (daily 0.015 mg/kg for 2 weeks, 0.015 mg/kg every 2 days for 1 week, 0.0075 mg/kg every 2 days for 1 week), was transiently effective in both cases. The second-round ACTH therapy consisted of the initial ACTH therapy protocol followed by weekly ACTH injections (0.015 mg/kg or 0.0075 mg/kg) for 1 year. Both cases were followed for at least 1 year after therapy.
In both patients, clinical seizures were completely controlled during and 1 year after the second-round AHCH therapy. Continuous epileptiform discharges disappeared, while intermittent interictal epileptiform discharges remained. Both patients showed some developmental gains after achieving seizure control. No serious side effects were recorded.
Further studies are warranted to determine if a long-term weekly ACTH is a safe and effective treatment for intractable epilepsy.
Brain and Development 08/2014; 37(4). DOI:10.1016/j.braindev.2014.07.004 · 1.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Recessive mutations in genes of the glycosylphosphatidylinositol (GPI)-anchor synthesis pathway have been demonstrated as causative of GPI deficiency disorders associated with intellectual disability, seizures, and diverse congenital anomalies. We performed whole exome sequencing in a patient with progressive encephalopathies and multiple dysmorphism with hypophosphatasia and identified novel compound heterozygous mutations, c.250G>T (p. Glu84*) and c.1342C>T (p. Arg488Trp), in PIGT encoding a subunit of the GPI transamidase complex. The surface expression of GPI-anchored proteins (GPI-APs) on patient granulocytes was lower than that of healthy controls. Transfection of the Arg488Trp mutant PIGT construct, but not the Glu84* mutant, into PIGT-deficient cells partially restored the expression of GPI-APs DAF and CD59. These results indicate that PIGT mutations caused neurological impairment and multiple congenital anomalies in this patient.