Identification of a common founder couple for 40 South African Afrikaner families with Parkinson's disease.

BACKGROUND: Afrikaners are a unique ethnic group in South Africa (SA) with well-documented ancestral records spanning a period of over 350 years. They are mainly descended from Dutch, German and French settlers to SA in the 17th and 18th centuries. Today several disorders in this population occur at relatively high frequencies as a result of founder effects.Objective. To determine whether a founder effect for Parkinson's disease (PD) is present in the Afrikaner population. METHODS: Study participants were recruited from the Movement Disorders Clinic at Tygerberg Hospital in Cape Town, SA, and from support groups of the Parkinson's Association of South Africa. Standard methods for genealogical research in SA on hereditary diseases were used including interviews and searches in sources such as state archives, the Huguenot Museum in Franschhoek, marriage and baptismal records, and tombstone inscriptions. RESULTS: For 40 of the PD families, there was only a single most recent ancestral couple common to all of the families. On average there are between three and four ancestral lines to the founder couple per proband (range 1 -14). CONCLUSION: If genetic studies confirm the presence of a founder effect for PD in Afrikaners, this would imply that there is a large number of individuals from this ethnic group who may potentially be at risk of developing this debilitating condition. This study illustrates and reinforces the concept that genealogical analysis is a powerful tool for identification of founder effects for various disorders in the Afrikaner population.

Screening of two indel polymorphisms in the 5'UTR of the DJ-1 gene in South African Parkinson's disease patients.

Mutations in the DJ-1 gene have been implicated in early-onset Parkinson's disease (PD). Two indel variants (g.168_185del and g.-6_+10del) in the 5'UTR of DJ-1 have been described. Genotyping of both variants in 402 South African PD patients of various ethnicities and 528 ethnically matched controls revealed that they are rare in the South African population. Further studies on these variants in other populations are warranted given their possible role in transcriptional regulation and DJ-1's critical role in alleviating oxidative stress.

Factors influencing the development of early- or late-onset Parkinson's disease in a cohort of South African patients.

BACKGROUND: Neurodegenerative disorders such as Parkinson's disease (PD) contribute significantly to global disease burden. PD can be categorised into early-onset PD (EOPD) with an age at onset (AAO) of ≤50 years and late-onset PD (LOPD) with an AAO of 50 years. AIMS: To identify factors influencing EOPD and LOPD development in a group of patients in South Africa (SA). METHODS: A total of 397 unrelated PD patients were recruited from the Movement Disorders Clinic at Tygerberg Hospital and via the Parkinson's Association of SA. Patient demographic and environmental data were recorded and associations with PD onset (EOPD v. LOPD) were analysed with a Pearson's Chi-squared test. The English- and Afrikaans-speaking (Afrikaner) white patients were analysed separately. RESULTS: Logistic regression analysis showed that ethnicity (p<0.001) and family history (p=0.004) were independently associated with AAO of PD. Average AAO was younger in black, coloured and Afrikaner patients than English-speaking white patients. A positive family history of PD, seen in 31.1% of LOPD patients, was associated with a younger AAO in the study population. CONCLUSIONS: These associations may be attributed to specific genetic and/or environmental risk factors that increase PD susceptibility and influence the clinical course of the disorder. More studies on PD in the unique SA populations are required to provide novel insights into mechanisms underlying this debilitating condition.

Mutations in the parkin gene are a minor cause of Parkinson's disease in the South African population.

The molecular basis of Parkinson's disease (PD) has been extensively studied in numerous population groups over the past decade. However, very little is known of the molecular etiology of PD in the South African population. We aimed to assess the genetic contribution of parkin mutations to PD pathology by determining the frequency of both point mutations and exon rearrangements in all 12 exons of the parkin gene in a group of 229 South African patients diagnosed with PD. This was done by performing high resolution melt (HRM) as well as multiplex ligation-dependent probe amplification (MLPA) analyses. In total, seven patients (3.1%; 7/229) had either compound heterozygous or homozygous mutations in parkin, and seven patients (3.1%) had heterozygous sequence variants. Two of the patients with parkin mutations are of Black African ancestry. Reverse-transcription PCR on lymphocytes obtained from two patients verified the presence of parkin mutations on both alleles. In conclusion, the present study reveals that mutations in the parkin gene are not a major contributor to PD in the South African population. Further investigations of the molecular etiology of PD in the unique South African population, particularly the Black African and mixed ancestry sub-populations, are warranted.

LRRK2 G2019S mutation: frequency and haplotype data in South African Parkinson's disease patients.

Mutations in the leucine-rich repeat kinase 2 gene (LRRK2) are the most significant genetic cause of Parkinson's disease (PD). The exact function of LRRK2 is currently unknown but the presence of multiple protein interaction domains including WD40 and ankyrin indicates that it may act a scaffold for assembly of a multi-protein signaling complex. The G2019S mutation in LRRK2 represents the most clinically relevant PD-causing mutation and has been found in both familial and sporadic forms of the disorder. This mutation is situated in the highly conserved kinase MAPKKK domain, and has been found in up to 40% of PD patients from North African Arabic, 30% of Ashkenazi Jewish and approximately 10% of Portuguese and Spanish populations. Although extensively investigated in numerous European and North American populations, studies on the frequency of G2019S in African countries have been rare. The present study is the first on the South African population. High-resolution melt analysis was used to identify the G2019S mutation and it was found in 2% (4/205) of the patients studied. G2019S was not found in any of the Black PD patients screened. In all four G2019S-positive probands the mutation was shown to be present on the common haplotype referred to as haplotype 1. This reveals that the four South African G2019S-positive probands (three Caucasian and one of mixed ancestry) share a common ancestor with the other haplotype 1-associated families reported worldwide.

Investigation of mitochondrial sequence variants associated with aminoglycoside-induced ototoxicity in South African TB patients on aminoglycosides.

A known side effect of aminoglycoside antibiotics is the development of permanent hearing loss. As South Africa is currently facing a tuberculosis (TB) epidemic, with an increasing number of multi-drug resistant tuberculosis (MDR-TB) infections, the use of aminoglycosides is on the increase. It is therefore important to determine whether the mitochondrial mutations associated with aminoglycoside-induced hearing loss occur at high frequencies in particular ethnic groups in our population. A total of 115 mainly MDR-TB patients all on aminoglycosides and 439 controls representative of the main ethnic groups in South Africa were screened for six mutations using the SNaPshot technique. Furthermore, the mitochondrial genomes of eight patients with ototoxicity were sequenced. Homoplasmic mutations were found in controls (A1555G in 0.9% of Black controls and A827G in 1.1% of Afrikaner controls) which reveal that a significant proportion of the South African population is genetically predisposed to developing aminoglycoside-induced hearing loss. The 961 delT+insC((n)) and T961G variants were found at frequencies of >1% indicating that both are probably non-pathogenic polymorphisms. Sequencing of the entire mitochondrial genome in eight patients did not reveal any mutations in the MT-RNR1 gene. However, two potentially pathogenic variants, T10114C (I19T in MT-ND3) and T15312C (I189T in MT-CYB) were found that may impact on the oxidative phosphorylation capacity and warrant further investigation for their possible role in this disorder. It is imperative that the genetic basis of this potentially preventable condition be investigated, particularly in countries where aminoglycosides are still commonly used, in order to identify individuals and/or ethnic groups who are at risk for this type of hearing loss.

Analysis of exon dosage using MLPA in South African Parkinson's disease patients.

Genomic rearrangements (exon dosage) are common mutations reported in Parkinson's disease (PD) patients. In the present study, we aimed to investigate the prevalence of genomic rearrangements in 88 South African patients with predominantly early-onset PD (age-at-onset

Molecular analysis of the parkin gene in South African patients diagnosed with Parkinson's disease.

Parkinson's disease (PD) is a common movement disorder which may arise from mutations in the parkin gene. To date, more than 100 different parkin mutations have been reported. The aim of the present study was to determine the frequency of point mutations and homozygous exon deletions in the parkin gene in a group of 91 South African patients diagnosed with PD. Mutation screening of the 12 exons of parkin was performed using single strand conformation polymorphism analysis and the high-resolution melt technique. Six different mutations were identified: four putative disease-causing missense heterozygous changes (H200Q, D280N, E310D and R402C) and two homozygous exon deletions (exons 3 and 4, and exon 4). The D280N and R402C variants have both previously been described but their pathogenic status has been equivocal. In the present study, the D280N variant was observed in three early onset PD-affected siblings and was not present in a 63-year-old unaffected sibling. This data provide further support for the pathogenicity of this variant which is situated within the first RING finger of the RING-box. None of the four missense variants were detected in over 100 ethnic-matched control chromosomes. We conclude that point mutations and homozygous exon deletions in the parkin gene are not a major cause of PD in the South African population. Further studies on this group of patients are needed to determine the contribution of heterozygous exon deletions and insertions in parkin. The present study is the first report on the molecular etiology of PD in South African patients.