Bülent Kara

Exome Sequencing Links Corticospinal Motor Neuron Disease to Common Neurodegenerative Disorders

Neurodegenerative Genetics The underlying genetics of neurodegenerative disorders tend not to be well understood. Novarino et al. (p. 506; see the Perspective by Singleton) investigated the underlying genetics of hereditary spastic paraplegia (HSP), a human neurodegenerative disease, by sequencing the exomes of individuals with recessive neurological disorders. Loss-of-function gene mutations in both novel genes and genes previously implicated for this condition were identified, and several were functionally validated. Analysis of hereditary spastic paraplegia genes identifies mutants involved in human neurodegenerative disease. [Also see Perspective by Singleton] Hereditary spastic paraplegias (HSPs) are neurodegenerative motor neuron diseases characterized by progressive age-dependent loss of corticospinal motor tract function. Although the genetic basis is partly understood, only a fraction of cases can receive a genetic diagnosis, and a global view of HSP is lacking. By using whole-exome sequencing in combination with network analysis, we identified 18 previously unknown putative HSP genes and validated nearly all of these genes functionally or genetically. The pathways highlighted by these mutations link HSP to cellular transport, nucleotide metabolism, and synapse and axon development. Network analysis revealed a host of further candidate genes, of which three were mutated in our cohort. Our analysis links HSP to other neurodegenerative disorders and can facilitate gene discovery and mechanistic understanding of disease.

A frameshift mutation of ERLIN2 in recessive intellectual disability, motor dysfunction and multiple joint contractures

We present a family afflicted with a novel autosomal recessive disease characterized by progressive intellectual disability, motor dysfunction and multiple joint contractures. No pathology was found by cranial imaging, electromyography and muscle biopsy, but electron microscopy in leukocytes revealed large vacuoles containing flocculent material. We mapped the disease gene by SNP genome scan and linkage analysis to an ∼0.80 cM and 1 Mb region at 8p11.23 with a multipoint logarithm of odds (LOD) score of 12. By candidate gene approach, we identified a homozygous two-nucleotide insertion in ERLIN2, predicted to lead to the truncation of the protein by about 20%. The gene encodes endoplasmic reticulum (ER) lipid raft-associated protein 2 that mediates the ER-associated degradation of activated inositol 1,4,5-trisphosphate receptors and other substrates.

New Hyperekplexia Mutations Provide Insight into Glycine Receptor Assembly, Trafficking, and Activation Mechanisms

Background: Hyperekplexia mutations have provided much information about glycine receptor structure and function. Results: We identified and characterized nine new mutations. Dominant mutations resulted in spontaneous activation, whereas recessive mutations precluded surface expression. Conclusion: These data provide insight into glycine receptor activation mechanisms and surface expression determinants. Significance: The results enhance our understanding of hyperekplexia pathology and glycine receptor structure-function. Hyperekplexia is a syndrome of readily provoked startle responses, alongside episodic and generalized hypertonia, that presents within the first month of life. Inhibitory glycine receptors are pentameric ligand-gated ion channels with a definitive and clinically well stratified linkage to hyperekplexia. Most hyperekplexia cases are caused by mutations in the α1 subunit of the human glycine receptor (hGlyR) gene (GLRA1). Here we analyzed 68 new unrelated hyperekplexia probands for GLRA1 mutations and identified 19 mutations, of which 9 were novel. Electrophysiological analysis demonstrated that the dominant mutations p.Q226E, p.V280M, and p.R414H induced spontaneous channel activity, indicating that this is a recurring mechanism in hGlyR pathophysiology. p.Q226E, at the top of TM1, most likely induced tonic activation via an enhanced electrostatic attraction to p.R271 at the top of TM2, suggesting a structural mechanism for channel activation. Receptors incorporating p.P230S (which is heterozygous with p.R65W) desensitized much faster than wild type receptors and represent a new TM1 site capable of modulating desensitization. The recessive mutations p.R72C, p.R218W, p.L291P, p.D388A, and p.E375X precluded cell surface expression unless co-expressed with α1 wild type subunits. The recessive p.E375X mutation resulted in subunit truncation upstream of the TM4 domain. Surprisingly, on the basis of three independent assays, we were able to infer that p.E375X truncated subunits are incorporated into functional hGlyRs together with unmutated α1 or α1 plus β subunits. These aberrant receptors exhibit significantly reduced glycine sensitivity. To our knowledge, this is the first suggestion that subunits lacking TM4 domains might be incorporated into functional pentameric ligand-gated ion channel receptors.

RESPONSE TO RITUXIMAB AND PREDNISOLONE FOR OPSOCLONUS-MYOCLONUS-ATAXIA SYNDROME IN A CHILD WITH GANGLIONEUROBLASTOMA

Opsoclonus-myoclonus-ataxia (OMA) syndrome is a rare neurobehavioral paraneoplastic disorder in children with neuroblastic tumors. The neurologic symptoms are generally treated with a number of immunosupressive and immunomodulating agents. A 4-year-old previously healthy male patient was admitted to the authors’ center with progressive ataxia, gait disturbance, diffuculty of speech, and opsoclonus. He had a diagnosis of ganglionueroblastoma at the thoracal paraspinal region. Following surgey, the patient received IVIG and prednisolone but his cerebellar symptoms progressed. Rituximab therapy was started and continued for total 8 weeks without any side effect. The authors observed excellent neurologic response in the patient at the 4th week of treatment. Rituximab is a new, promising, and safe therapy for OMA syndrome in children with neuroblastoma.

Using the Modified Checklist for Autism in Toddlers in a well-child clinic in Turkey: Adapting the screening method based on culture and setting:

We aimed to adapt the Modified Checklist for Autism in Toddlers to Turkish culture. The Modified Checklist for Autism in Toddlers was filled out independently by 191 parents while they were waiting for the well-child examination of their child. A high screen-positive rate was found. Because of this high false-positive rate, a second study was done in which the Modified Checklist for Autism in Toddlers was administered by health-care staff in a short interview with two groups of parents. The first group (the high-risk group) comprised 80 children aged 18–36 months, who were initially diagnosed with pervasive developmental disorders. The second group (the low-risk group) comprised 538 children of the same age, who were followed regularly by the well-child clinic. Two screen positives were found in the low-risk group. These two children, a random sample of 120 children from the low-risk group, and all the high-risk group were invited to a clinical evaluation. The diagnostic power of the Modified Checklist for Autism in Toddlers was assessed against clinical diagnosis and the Childhood Autism Rating Scale. The positive predictive value of the Modified Checklist for Autism in Toddlers was found to be 75%. Our findings led us to conclude that the Modified Checklist for Autism in Toddlers is a useful tool in Turkey for screening of pervasive developmental disorders in primary care, but in our culture, it is completed more accurately when health-care personnel ask the parents the questions. This study shows that Modified Checklist for Autism in Toddlers screening should be adapted based on culture and setting.

Whole mitochondrial genome analysis of a family with NARP/MILS caused by m.8993T>C mutation in the MT-ATP6 gene.

Mutations in mitochondrial DNA (mtDNA) encoded nucleotide 8993 can cause NARP syndrome (neuropathy, ataxia, and retinitis pigmentosa) or MILS (maternally inherited Leigh syndrome). The rare T8993C mutation in the MT-ATP6 gene is generally considered to be clinically milder, but there is marked clinical heterogeneity ranging from asymptomatic carriers to fatal infantile Leigh syndrome. Clinical heterogeneity has mostly been attributed to mtDNA heteroplasmy, but environmental, autosomal, tissue-specific factors, nuclear modifier genes, and mtDNA variations may also modulate disease expression. Here, we report the results of whole mitochondrial genome analysis of a family with m.8993T>C mutation in the MT-ATP6 gene and associated with NARP/MILS, and discuss the familial inheritance, effects of variation in combinations and heteroplasmy levels on the clinical findings. The whole mitochondrial genome was sequenced with ~182× average depth of coverage per sample with next-generation sequencing technology. Thus, all heteroplasmic (>%10) and homoplasmic variations were determined (except for 727C insertion) and classified according to the associations with mitochondrial diseases.

Intravenous cyclophosphamide is the drug of choice for steroid dependent nephrotic syndrome

Abstract Background : Steroid dependency is a major problem seen after therapy for idiopathic nephrotic syndrome in childhood. Although there is consensus about the usage of cyclophosphamide (CYC) in frequent relapsers, there is still a controversy concerning its usage in steroid‐dependent nephrotic syndrome (SDNS).

Adult phenotype and further phenotypic variability in SRD5A3-CDG

BackgroundSRD5A3 is responsible for SRD5A3-CDG, a type of congenital disorder of glycosylation, and mutations have been reported in 15 children. All the mutations are recessive and truncating.Case presentationWe present 2 brothers at the age of 38 and 40 years with an initial diagnosis of cerebellar ataxia. We found the candidate disease loci via linkage analysis using data from single nucleotide polymorphism genome scans and homozygous truncating mutation SRD5A3 p.W19X, which was previously reported in 3 unrelated children, by exome sequencing.Clinical investigations included physical and ocular examinations and blood tests. Severe ocular involvement with retinal bone spicule pigmentation and optic atrophy are the most prominent disabling clinical features of the disease. The serum transferrin isoelectric focusing (TIEF) pattern is abnormal in the patient investigated.ConclusionOur patients are older, with later onset and milder clinical phenotypes than all patients with SRD5A3-CDG reported so far. They also have atypical ocular findings and variable phenotypes. Our findings widen the spectrum of phenotypes resulting from SRD5A3 mutations and the clinical variability of SRD5A3-CDG, and suggest screening for SRD5A3 mutations in new patients with at least a few of the clinical symptoms of SRD5A3-CDG.

Clinical outcomes in children with herpes simplex encephalitis receiving steroid therapy

BACKGROUND Herpes simplex virus encephalitis (HSE) is a significant cause of morbidity and mortality. Neurologic sequelae are common even after early initiation of acyclovir treatment. The host immune response during HSE can also lead to brain damage. There are an increasing number of reports favoring steroid use in HSE. OBJECTIVES We aimed to compare the prognosis of children with HSE with and without steroid therapy. STUDY DESIGN We retrospectively screened our hospital archive from 2009 to 2014 for patients diagnosed with HSE with a positive result for herpes simplex virus polymerase chain reaction in cerebrospinal fluid. Patients ≥1 month and ≤18 years at diagnosis were included in the study. Clinical outcomes in terms of cognitive function, motor function, electroencephalographic findings, seizure frequency, and radiologic findings were compared in patients who received adjuvant steroid therapy with those who did not. RESULTS Six patients (1 boy, 5 girls; aged 4 months to 10 years) were included. Overall symptom duration before hospital admission was ≤5days. Patients received acyclovir treatment for 21-28days. Three received steroid therapy early during the disease and three patients did not. No adverse effects related to steroids were observed. Follow-up duration was 6 months to 5 years. All patients had radiologic sequelae of encephalitis. Cognition, motor function, and seizure control were better in patients who received steroid therapy. CONCLUSIONS Adjuvant steroid therapy seems to be effective in decreasing morbidity in children with HSE but the radiologic sequelae were the same in both groups.

Transient peripheral leukocytosis in children with afebrile seizures.

The purpose of this study was (1) to demonstrate whether peripheral blood leukocytosis accompanies first afebrile seizures without bacterial infection, (2) to investigate the duration of leukocytosis, and (3) to assess the relationship between peripheral blood leukocytosis and seizure characteristics. Complete blood count was routinely obtained from all the patients. Blood and urine cultures were obtained from patients with leukocytosis. On the 24th hour of admission, a second complete blood count was obtained from patients with initial leukocytosis. Sixty-two children aged 4.0 ± 3.6 years (range, 6 months—13 years)—31 boys (50%) and 31 girls (50%)—enrolled in the study. The findings showed that peripheral blood leukocytosis was found in 8% of afebrile children without status epilepticus and 41.6% of afebrile children with status epilepticus. An interesting finding of the study was that peripheral blood leukocytosis accompanied by afebrile seizures subsided in 24 hours. Transient leukocytosis could be found in children with afebrile seizures without bacterial infection.