Amanda Singleton

Early-onset Parkinson's disease caused by a compound heterozygous DJ-1 mutation.

Mutations in DJ‐1 have been linked to an autosomal recessive form of early‐onset parkinsonism. To identify mutations causing Parkinsons disease (PD), we sequenced exons 1 through 7 of DJ‐1 in 107 early‐onset (age at diagnosis up to 50 years) PD subjects. One subject had a frameshift mutation in the first coding exon and an exon 7 splice mutation both predicted to result in a loss of functional protein. This subject was diagnosed with probable PD at age 24 years with asymmetric onset and an excellent response to levodopa therapy. Our observations suggest that sequence alterations in DJ‐1 are a rare cause of early‐onset PD.

Spinocerebellar ataxia type 2 with parkinsonism in ethnic Chinese

Objective: To describe the clinical and molecular genetic analysis of a large family of northern Chinese descent with a mutation at the SCA2 locus causing carbidopa-levodopa–responsive parkinsonism. Background: Most causes of parkinsonism remain unknown. However, molecular genetic analysis of families with parkinsonism has recently identified five distinct loci and pathogenic mutations in four of those. Additionally, some of the spinocerebellar ataxia syndromes (SCA), particularly Machado–Joseph syndrome (SCA3), are known to cause parkinsonism. Spinocerebellar ataxia type 2 (SCA2) has not previously been described as causing a typical dopamine-responsive asymmetric PD phenotype. Methods: A large family was evaluated clinically and molecularly for apparent autosomal dominant parkinsonism. Results: The phenotype includes presentation consistent with typical dopamine-responsive parkinsonism. Other presentations in this family include a parkinsonism/ataxia phenotype, which is classic for SCA2 and parkinsonism, resembling progressive supranuclear palsy. Conclusions: Patients presenting with a family history of parkinsonism, including familial progressive supranuclear palsy and PD, should be tested for the spinocerebellar ataxia type 2 expansion.

Genome-wide association study of Tourette's syndrome

Tourettes syndrome (TS) is a developmental disorder that has one of the highest familial recurrence rates among neuropsychiatric diseases with complex inheritance. However, the identification of definitive TS susceptibility genes remains elusive. Here, we report the first genome-wide association study (GWAS) of TS in 1285 cases and 4964 ancestry-matched controls of European ancestry, including two European-derived population isolates, Ashkenazi Jews from North America and Israel and French Canadians from Quebec, Canada. In a primary meta-analysis of GWAS data from these European ancestry samples, no markers achieved a genome-wide threshold of significance (P<5 × 10−8); the top signal was found in rs7868992 on chromosome 9q32 within COL27A1 (P=1.85 × 10−6). A secondary analysis including an additional 211 cases and 285 controls from two closely related Latin American population isolates from the Central Valley of Costa Rica and Antioquia, Colombia also identified rs7868992 as the top signal (P=3.6 × 10−7 for the combined sample of 1496 cases and 5249 controls following imputation with 1000 Genomes data). This study lays the groundwork for the eventual identification of common TS susceptibility variants in larger cohorts and helps to provide a more complete understanding of the full genetic architecture of this disorder.

Profile of families with parkinsonism‐predominant spinocerebellar ataxia type 2 (SCA2)

Spinocerebellar ataxia type 2 (SCA2) has been recognized recently as an uncommon cause of parkinsonism, an alternate presentation to the typical cerebellar disorder. This research review summarizes the existing literature on parkinsonism‐predominant presentation SCA2 and presents new clinical cases of patients with this condition. Various phenotypes are noted in this subtype of SCA2, including parkinsonism indistinguishable from idiopathic Parkinsons disease (PD), parkinsonism plus ataxia, motor neuron disease, and postural tremor. In several kindreds with multiple affected family members, the SCA2 expansion segregated with disease; in addition, several single cases of parkinsonism with and without a family history are also described. The number of repeats in symptomatic patients ranged from 33 to 43. Interruption of the CAG repeat with CAA, CGG, or CCG was found in some individuals, possibly stabilizing the repeat structure and accounting for the relative stability of the repeat size across generations in some families; allele length is not necessarily indicative of trinucleotide repeat architecture. Positron emission tomography scanning in one family showed reduced fluorodopa uptake and normal to increased raclopride binding with a rostrocaudal gradient similar to that found in idiopathic PD. This review emphasizes the importance of testing for SCA2 in patients with parkinsonism and a family history of neurodegenerative disorders. Testing for SCA2 is also important in studies of inherited parkinsonism.

SCA2 may present as levodopa-responsive parkinsonism

Some kindreds with familial parkinsonism exhibit genetic anticipation, suggesting possible involvement of trinucleotide repeat expansion. Recent reports have shown trinucleotide repeat expansions in the spinocerebellar ataxia 2 (SCA2) gene in patients with levodopa‐responsive parkinsonism. We tested 136 unrelated patients with familial parkinsonism for SCA2 mutations. Two probands had borderline mutations; the rest were normal. (≤31 repeats is normal, 32–35 is borderline, ≥36 is pathogenic). The expanded allele segregated with neurological signs in one kindred. The absence of borderline mutations in the normal population, and the co‐segregation of the expanded allele with neurological signs in one kindred suggest that SCA2 mutations may be responsible for a subset of familial parkinsonism.

The genetics of ischaemic stroke

Abstract.  Matarin M, Singleton A, Hardy J, Meschia J (Laboratory of Neurogenetics, Bethesda, MD, USA; UCL Institute of Neurology, London, UK; Mayo Clinic, Jacksonville, FL, USA). The genetics of ischaemic stroke (Review). J Intern Med 2010; 267: 139–155.

Informed choice in direct-to-consumer genetic testing (DTCGT) websites: a content analysis of benefits, risks, and limitations

An informed choice about health-related direct-to-consumer genetic testing (DTCGT) requires knowledge of potential benefits, risks, and limitations. To understand the information that potential consumers of DTCGT services are exposed to on company websites, we conducted a content analysis of 23 health-related DTCGT websites. Results revealed that benefit statements outweighed risk and limitation statements 6 to 1. The most frequently described benefits were: 1) disease prevention, 2) consumer education, 3) personalized medical recommendations, and 4) the ability to make health decisions. Thirty-five percent of websites also presented at least one risk of testing. Seventy-eight percent of websites mentioned at least one limitation of testing. Based on this information, potential consumers might get an inaccurate picture of genetic testing which could impact their ability to make an informed decision. Practices that enhance the presentation of balanced information on DTCGT company websites should be encouraged.

Analysis of SCA-2 and SCA-3 repeats in Parkinsonism: evidence of SCA-2 expansion in a family with autosomal dominant Parkinson's disease.

The spinocerebellar ataxias (SCAs) are progressive neurodegenerative disorders linked to more than 20 genetic loci. Most often, these diseases are caused by expansion of triplet repeats encoding polyglutamine (polyQ) tracts. The phenotype is variable and can cause a disease that overlaps clinically with Parkinsons disease (PD). l-Dopa-responsive parkinsonism with minimal cerebellar deficits has been described in SCA2 and SCA3. In order to define if mutation at these loci is a common cause of clinically defined parkinsonism we typed the SCA-2 and SCA-3 repeats for expansion in a series of 280 patients diagnosed with PD or parkinsonism. We identified one pathogenic expansion in SCA-2 in a North American family with autosomal dominant parkinsonism.

Analysis of familial and sporadic restless legs syndrome in age of onset, gender, and severity features.

Restless Legs Syndrome is characterized by the irresistible, often indescribable unpleasant urge to move the limbs while resting. It has an estimated prevalence of ~29.3 % in US private practice. Restless Legs Syndrome often has a familial component; whether the familial and non-familial forms differ in terms of clinical features has previously been investigated, with the only significant factor emerging as younger age at onset in familial cases. Our study further explores a possible underlying difference between familial and sporadic forms of RLS by comparing familial RLS with sporadic RLS in terms of demographic and clinical features including subject gender, age of onset, and severity measures based an the IRLSSG severity scale. Both gender and family history are significant predictors of onset age in an overall model and also significant when analyzed independently. Participants who reported more severe RLS symptoms were significantly younger in age and progressed more rapidly. Two variables from the IRLSSG severity scale were significantly associated with age of onset when tested independently: discomfort and the urge to move the limb for relief. Our analysis supports the prevailing hypothesis that RLS is divided into earlier onset disease with a clear genetic component and later onset disease wich unclear etiology, and that one or more endophenotypes might exist within the disorder which could further characterize these subjects for future genetic studies.

Clinical Features, with Video Documentation, of the original Familial Lewy Body Parkinsonism caused by α-Synuclein Triplication (Iowa Kindred)

This family has autosomal dominant parkinsonism due to α-synuclein triplication. Dopamine-responsive parkinsonism, cognitive difficulties, RBD, and dysautonomia are common. End-stage illness includes contractures, myoclonus, and severe motor and cognitive impairment. Of note, there was pre-symptomatic amphetamine/cocaine use in two of the cases described.