Variation in Exon 29 of the NOS1 Gene Does Not Contribute to Parkinson's Disease in the North Karnataka Population

INTRODUCTION

Nitric oxide (NO) overproduction has been found to have neurotoxic effects on the brain. Moreover, in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induced, the suppression of the NO-synthesizing enzymes, such as neuronal nitric oxide synthase (nNOS) and inducible NOS (iNOS), has neuroprotective benefits in Parkinson's disease (PD). These findings imply that NOS may have a role in regulating the nigral dopaminergic neurons' tolerance to environmental stressors in PD.

OBJECTIVE

In the present study, we investigated variations in the NOS1 gene that may raise the likelihood of PD.

METHODS

PD patients who visited the neurology departments of several medical colleges and hospitals in North Karnataka, India, between 2009 and 2011 were included in the study. The detailed clinic pathological details were obtained from 100 PD patients. Genomic DNA was isolated using the kit method followed by the evaluation of the quality and quantity of isolated gDNA. Polymerase chain reaction (PCR) amplification of exon 29 was performed, and sequencing was performed using the Applied Biosystems ABI 3500 Sanger sequencing platform.

RESULTS

The present study is comprised of 100 PD patients, which includes 65 males and 35 females. There were 64 sporadic, 34 idiopathic, and two familial PD cases. The majority (67.1%) of PD cases were from metropolitan areas. Community-based segregation showed that the maximum cases were from Hindu Lingayat. A proportion (90.8%) of the patients had tremors, 32.7% of them displayed slowness in their daily tasks, and 8.1% of them had dyskinesia. Molecular analysis showed two untranslated region (UTR) variations g.151787 del T (rs1434015950) and g.151745 C>T (rs2682826) in our study group.

CONCLUSION

The absence of mutations in the targeted NOS1 gene in the PD patients from North Karnataka shows the involvement of other genes in the molecular pathophysiology. Thus, it is crucial to screen other possible genes using cutting-edge technology to obtain a clear picture of the genetics of PD.

Genetic Architecture of Parkinson's Disease in the Indian Population: Harnessing Genetic Diversity to Address Critical Gaps in Parkinson's Disease Research

Over the past two decades, our understanding of Parkinson's disease (PD) has been gleaned from the discoveries made in familial and/or sporadic forms of PD in the Caucasian population. The transferability and the clinical utility of genetic discoveries to other ethnically diverse populations are unknown. The Indian population has been under-represented in PD research. The Genetic Architecture of PD in India (GAP-India) project aims to develop one of the largest clinical/genomic bio-bank for PD in India. Specifically, GAP-India project aims to: (1) develop a pan-Indian deeply phenotyped clinical repository of Indian PD patients; (2) perform whole-genome sequencing in 500 PD samples to catalog Indian genetic variability and to develop an Indian PD map for the scientific community; (3) perform a genome-wide association study to identify novel loci for PD and (4) develop a user-friendly web-portal to disseminate results for the scientific community. Our "hub-spoke" model follows an integrative approach to develop a pan-Indian outreach to develop a comprehensive cohort for PD research in India. The alignment of standard operating procedures for recruiting patients and collecting biospecimens with international standards ensures harmonization of data/bio-specimen collection at the beginning and also ensures stringent quality control parameters for sample processing. Data sharing and protection policies follow the guidelines established by local and national authorities.We are currently in the recruitment phase targeting recruitment of 10,200 PD patients and 10,200 healthy volunteers by the end of 2020. GAP-India project after its completion will fill a critical gap that exists in PD research and will contribute a comprehensive genetic catalog of the Indian PD population to identify novel targets for PD.

Whole genome sequencing for the genetic diagnosis of heterogenous dystonia phenotypes

INTRODUCTION

Dystonia is a clinically and genetically heterogeneous disorder and a genetic cause is often difficult to elucidate. This is the first study to use whole genome sequencing (WGS) to investigate dystonia in a large sample of affected individuals.

METHODS

WGS was performed on 111 probands with heterogenous dystonia phenotypes. We performed analysis for coding and non-coding variants, copy number variants (CNVs), and structural variants (SVs). We assessed for an association between dystonia and 10 known dystonia risk variants.

RESULTS

A genetic diagnosis was obtained for 11.7% (13/111) of individuals. We found that a genetic diagnosis was more likely in those with an earlier age at onset, younger age at testing, and a combined dystonia phenotype. We identified pathogenic/likely-pathogenic variants in ADCY5 (n = 1), ATM (n = 1), GNAL (n = 2), GLB1 (n = 1), KMT2B (n = 2), PRKN (n = 2), PRRT2 (n = 1), SGCE (n = 2), and THAP1 (n = 1). CNVs were detected in 3 individuals. We found an association between the known risk variant ARSG rs11655081 and dystonia (p = 0.003).

CONCLUSION

A genetic diagnosis was found in 11.7% of individuals with dystonia. The diagnostic yield was higher in those with an earlier age of onset, younger age at testing, and a combined dystonia phenotype. WGS may be particularly relevant for dystonia given that it allows for the detection of CNVs, which accounted for 23% of the genetically diagnosed cases.

A Novel Homozygous Mutation in the FUCA1 Gene Highlighting Fucosidosis as a Cause of Dystonia: Case Report and Literature Review

BACKGROUND

Fucosidosis is a rare lysosomal disorder caused by mutations in the FUCA1 gene. We describe here a novel homozygous mutation in FUCA1 in an Indian fucosidosis case. Furthermore, we summarize the clinical and genetic findings in the most recently reported individuals with fucosidosis.

CASE

The proband is an 8-year-old boy born to consanguineous parents. He had generalized dystonia and bilateral spasticity as well as coarse facies, dysostosis multiplex, recurrent infections, angiokeratoma corporis diffusum, and visceromegaly. Whole exome sequencing analysis detected a homozygous canonical splice variant in the FUCA1 gene [Chr1(GRCh37):g.24172346C > T; NM_000147.4:c.1261-1G > A], not previously reported as causative of a human phenotype. Low levels of α-fucosidase in patient leukocytes and a positive qualitative urine based thin layer chromatography test for fucosidosis confirmed the diagnosis. Our literature review identified 89 cases of fucosidosis since the last major review. We show that dystonia is a rare manifestation (12%) and that only a small minority of cases receive treatment with transplantation (3.37%).

CONCLUSION

We report a novel homozygous mutation in FUCA1 as the cause of severe neurological phenotype including generalized dystonia. Early recognition of fucosidosis may be important for consideration of promising treatment options, such as bone marrow transplantation.

A Compound Heterozygote for GCH1 Mutation Represents a Case of Atypical Dopa-Responsive Dystonia

Dopa-responsive dystonia (DRD), a movement disorder, is characterized by young onset dystonia and dramatic response to levodopa treatment. However, the wide range of phenotypic spectrum of the disease often leads to misdiagnosis. DRD is usually caused by mutation in GCH1 gene coding for GTP cyclohydrolase 1 (GTPCH1) enzyme, which is involved in biosynthesis of tetrahydrobiopterin (BH4) and dopamine. In this study, the entire GCH1 gene was screened in 14 Indian DRD patients and their family members. A family was identified where the proband was found to be a compound heterozygote for GCH1 (p.R184H and p.V204I) variants; the former variant being inherited from the father and the latter from the mother. All other family members harboring one of these GCH1 variants were asymptomatic except for one (heterozygous for p.R184H) who was diagnosed with DRD. In silico analyses predicted these two variants to be pathogenic and disruptive to GCH1enzymatic activity. This proband was misdiagnosed as cerebral palsy and remained untreated for 25 years. He developed retrograde movements and gait problems in lower limbs, deformity in upper limbs, and difficulty in swallowing, and became mute. However, most of his symptoms were alleviated upon levodopa administration. Our study confirms the variability of DRD phenotype and the reduced penetrance of GCH1 mutations. It also emphasizes the need of molecular diagnostic test and L-dopa trial especially for those with atypical DRD phenotype.

Defining the genetic basis of early onset hereditary spastic paraplegia using whole genome sequencing

We performed whole genome sequencing (WGS) in nine families from India with early-onset hereditary spastic paraplegia (HSP). We obtained a genetic diagnosis in 4/9 (44 %) families within known HSP genes (DDHD2 and CYP2U1), as well as perixosomal biogenesis disorders (PEX16) and GM1 gangliosidosis (GLB1). In the remaining patients, no candidate structural variants, copy number variants or predicted splice variants affecting an extended candidate gene list were identified. Our findings demonstrate the efficacy of using WGS for diagnosing early-onset HSP, particularly in consanguineous families (4/6 diagnosed), highlighting that two of the diagnoses would not have been made using a targeted approach.

Spinocerebellar ataxia type 7: Report of an Indian family

Spinocerebellar ataxia type 7 (SCA7) is a form of autosomal dominant cerebellar ataxia which is associated with pigmentary retinal degeneration. It is known for its world-wide rarity except in the Scandinavian countries. It is very rarely reported from India and the neighbouring Asian countries. The present report describes the neurogenetic findings of a family of SCA7, from the northern part of Karnataka in South India. It documents the wide intrafamilial phenotypic variability, which could be correlated with the CAG repeat counts and phenomenon of anticipation. Genotype phenotype correlation highlighted certain disparities in comparison with the previous studies. The report highlights the need for multiethnic population studies and the role of genetic counseling and prenatal testing in SCA7 patients.

PRRT2 gene mutations: from paroxysmal dyskinesia to episodic ataxia and hemiplegic migraine

OBJECTIVE

The proline-rich transmembrane protein (PRRT2) gene was recently identified using exome sequencing as the cause of autosomal dominant paroxysmal kinesigenic dyskinesia (PKD) with or without infantile convulsions (IC) (PKD/IC syndrome). Episodic neurologic disorders, such as epilepsy, migraine, and paroxysmal movement disorders, often coexist and are thought to have a shared channel-related etiology. To investigate further the frequency, spectrum, and phenotype of PRRT2 mutations, we analyzed this gene in 3 large series of episodic neurologic disorders with PKD/IC, episodic ataxia (EA), and hemiplegic migraine (HM).

METHODS

The PRRT2 gene was sequenced in 58 family probands/sporadic individuals with PKD/IC, 182 with EA, 128 with HM, and 475 UK and 96 Asian controls.

RESULTS

PRRT2 genetic mutations were identified in 28 out of 58 individuals with PKD/IC (48%), 1/182 individuals with EA, and 1/128 individuals with HM. A number of loss-of-function and coding missense mutations were identified; the most common mutation found was the p.R217Pfs*8 insertion. Males were more frequently affected than females (ratio 52:32). There was a high proportion of PRRT2 mutations found in families and sporadic cases with PKD associated with migraine or HM (10 out of 28). One family had EA with HM and another large family had typical HM alone.

CONCLUSIONS

This work expands the phenotype of mutations in the PRRT2 gene to include the frequent occurrence of migraine and HM with PKD/IC, and the association of mutations with EA and HM and with familial HM alone. We have also extended the PRRT2 mutation type and frequency in PKD and other episodic neurologic disorders.

Sepiapterin reductase deficiency: a treatable mimic of cerebral palsy

OBJECTIVE

Sepiapterin reductase deficiency (SRD) is an under-recognized levodopa-responsive disorder. We describe clinical, biochemical, and molecular findings in a cohort of patients with this treatable condition. We aim to improve awareness of the phenotype and available diagnostic and therapeutic strategies to reduce delayed diagnosis or misdiagnosis, optimize management, and improve understanding of pathophysiologic mechanisms.

METHODS

Forty-three individuals with SRD were identified from 23 international medical centers. The phenotype and treatment response were assessed by chart review using a detailed standardized instrument and by literature review for cases for which records were unavailable.

RESULTS

In most cases, motor and language delays, axial hypotonia, dystonia, weakness, oculogyric crises, and diurnal fluctuation of symptoms with sleep benefit become evident in infancy or childhood. Average age of onset is 7 months, with delay to diagnosis of 9.1 years. Misdiagnoses of cerebral palsy (CP) are common. Most patients benefit dramatically from levodopa/carbidopa, often with further improvement with the addition of 5-hydroxytryptophan. Cerebrospinal fluid findings are distinctive. Diagnosis is confirmed by mutation analysis and/or enzyme activity measurement in cultured fibroblasts.

INTERPRETATION

Common, clinical findings of SRD, aside from oculogyric crises and diurnal fluctuation, are nonspecific and mimic CP with hypotonia or dystonia. Patients usually improve dramatically with treatment. Consequently, we recommend consideration of SRD not only in patients with levodopa-responsive motor disorders, but also in patients with developmental delays with axial hypotonia, and patients with unexplained or atypical presumed CP. Biochemical investigation of cerebrospinal fluid is the preferred method of initial investigation. Early diagnosis and treatment are recommended to prevent ongoing brain dysfunction.

Acute movement disorder with bilateral basal ganglia lesions in diabetic uremia

Acute movement disorder associated with symmetrical basal ganglia lesions occurring in the background of diabetic end stage renal disease is a recently described condition. It has distinct clinico-radiological features and is commonly described in Asian patients. We report the first Indian case report of this potentially reversible condition and discuss its various clinico-radiological aspects.

Novel movement disorder of the lower lip: Is it epilepsia partialis continua? Clues from a secondary case

A 28-year-old woman developed an acute-onset novel movement disorder of the lower lip mimicking focal dystonia. Investigations showed it to be a presentation of epilepsia partialis continua occurring in association with agenesis of the corpus callosum. It responded favorably to anti-epileptic drug therapy. Recently, Kleopa and Kyriakides reported on 4 patients who developed sudden-onset movement disorder characterized by a tonic sustained, lateral and outward protrusion of half of the lower lip. They failed to find any causative factors, despite extensive investigation. Treatment with anticholinergics, clonazepam, and botulinum toxin injection failed to improve the movement disorder. I present an additional case of similar focal movement disorder occurring in the presence of agenesis of the corpus callosum. A scalp electroencephalogram revealed focal epileptic activity, and the movement disorder responded favorably to treatment with antiepileptic drugs.

Asymmetrical awake bruxism associated with multiple system atrophy

We describe a 51-year-old man who developed awake bruxism during the course of multiple system atrophy. Electromyographic studies revealed side-to-side amplitude asymmetry of the bursts of motor activity. The bruxism responded favourably to low-dose levodopa-carbidopa therapy. Possible mechanisms of this rare association are discussed.

Parkinsonism associated with Addison's disease

We describe a 35-year-old woman who developed parkinsonism in association with Addison's disease. The parkinsonism disappeared following treatment for Addison's disease without the use of antiparkinsonian drugs. This association stands unique although the pathophysiology remains unclear.

Mutation analysis of the sodium/hydrogen exchanger gene (NHE5) in familial paroxysmal kinesigenic dyskinesia

Familial Paroxysmal Kinesigenic Dyskinesia (PKD) is an autosomal dominant condition characterized by attacks of dystonia or chorea triggered by sudden movements. Recently two separate loci for PKD, Episodic Kinesigenic Dyskinesia 1 (EKD1) and Episodic Kinesigenic Dyskinesia 2 (EKD2), have been mapped to chromosome 16 but the causative genes have not been identified. The Na(+)/H(+) exchanger gene (NHE5) involved in regulating intracellular pH lies in the EKD2 region. The coding region of the NHE5 gene in familial PKD was sequenced. We did not identify any mutations in the exons, intron/exon boundaries or the 5' and 3'UTR. This excludes mutations in the coding region of the NHE5 gene as a cause for familial PKD, but does not rule out a possible role of sequence variants in introns or regulatory regions.

Genetic and clinical heterogeneity in paroxysmal kinesigenic dyskinesia: evidence for a third EKD gene

Paroxysmal kinesigenic dyskinesia (PKD) is characterised by paroxysms of choreic, dystonic, ballistic, or athetoid movements. The attacks typically last seconds to minutes in duration and are induced by sudden voluntary movement. PKD loci have been identified on chromosome 16. We present the clinical and genetic details of two British and an Indian family with PKD. Linkage to the PKD loci on chromosome 16 has been excluded in one of these families, providing evidence for a third loci for PKD. Detailed clinical descriptions highlight the presence of both adolescent and infantile seizures in some of the PKD families. This study attempts to clarify the relationship of adolescent and infantile seizures to PKD and provides evidence that PKD is both genetically and clinically heterogeneous.

A second paroxysmal kinesigenic choreoathetosis locus (EKD2) mapping on 16q13-q22.1 indicates a family of genes which give rise to paroxysmal disorders on human chromosome 16

Paroxysmal kinesigenic choreoathetosis (PKC) is a rare paroxysmal movement disorder characterized by recurrent and brief attacks of choreiform or dystonic movements triggered or exacerbated by sudden voluntary movements. Some patients with PKC also have a history of infantile afebrile convulsions. PKC can be sporadic, or familial with autosomal dominant inheritance. PKC has been mapped to the pericentromeric region of human chromosome 16 in several Japanese families and in an African-American family, to regions which overlap by 9.8 cM (centiMorgan). Both regions overlap by 3.4 cM with a region containing a gene responsible for 'infantile convulsions and paroxysmal choreoathetosis' (ICCA). We have identified a second PKC locus (EKD2) on the long arm of chromosome 16 in a large Indian family with PKC. A maximum two-point LOD score of 3.66 (recombination fraction = 0.00, penetrance = 0.80) was obtained between PKC and D16S419. Haplotype and recombinant analysis localized EKD2 to a 15.8 cM region between D16S685 and D16S503. This region does not overlap with that identified in Japanese families, or with the ICCA locus. These results exclude one locus on chromosome 16 which causes both the ICCA and PKC syndromes; this suggests that there may be a cluster of genes on human chromosome 16 which lead to paroxysmal disorders.

"Ease of falling" syndrome associated with subdural haematoma

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"Fou rire prodromique" heralding a brainstem stroke

A patient manifested pathological laughter heralding the onset of brainstem stroke leading to a "locked-in" state. The pathological laughter did not recur. MRI revealed a bilateral ventral pontine infarct. The clinico-anatomical correlations of this rare phenomenon of fou rire prodromique are discussed.

Paroxysmal hemidystonia induced by prolonged exercise and cold

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Bickerstaff's brainstem encephalitis associated with typhoid fever

A 14 year old boy developed the syndrome of Bickerstaff's brainstem encephalitis during the course of bacteriologically proved typhoid fever. The clinical course and the results of various neurological investigations are detailed. This report adds a further manifestation to the published neuropsychiatric complications of typhoid fever.