Chromosome 9 ALS and FTD locus is probably derived from a single founder

Reta Lila Weston Research Laboratories, Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London, UK.
Neurobiology of aging (Impact Factor: 5.01). 09/2011; 33(1):209.e3-8. DOI: 10.1016/j.neurobiolaging.2011.08.005
Source: PubMed


We and others have recently reported an association between amyotrophic lateral sclerosis (ALS) and single nucleotide polymorphisms on chromosome 9p21 in several populations. Here we show that the associated haplotype is the same in all populations and that several families previously shown to have genetic linkage to this region also share this haplotype. The most parsimonious explanation of these data are that there is a single founder for this form of disease.

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Available from: Ammar Al-Chalabi, Jan 20, 2014
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    • "Indeed the C9ORF72 expansion was identified through study of a risk haplotype at the 9p21 locus [17]. Following the screening of numerous populations for the C9ORF72 expansion, it has been shown to occur in the presence of the same haplotype in all populations considered, or with the A-allele of rs389942, which is associated with the haplotype [18], including populations which might be considered relatively genetically different from Scandinavia such as Japan [16]. Data analysis of a 42-SNP haplotype from carriers of the expansion in Europe, USA and Australia led to the hypothesis that there was a common founder carrying the pathogenic mutation approximately 100 generations ago in Northern Europe and this expansion then spread across the world [5]. "
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    ABSTRACT: The GGGGCC (G4C2) repeat expansion in C9ORF72 is the most common cause of familial amyotrophic lateral sclerosis (ALS), frontotemporal lobar dementia (FTLD) and ALS-FTLD, as well as contributing to sporadic forms of these diseases. Screening of large cohorts of ALS and FTLD cohorts has identified that C9ORF72-ALS is represented throughout the clinical spectrum of ALS phenotypes, though in comparison with other genetic subtypes, C9ORF72 carriers have a higher incidence of bulbar onset disease. In contrast, C9ORF72-FTLD is predominantly associated with behavioural variant FTD, which often presents with psychosis, most commonly in the form of hallucinations and delusions. However, C9ORF72 expansions are not restricted to these clinical phenotypes. There is a higher than expected incidence of parkinsonism in ALS patients with C9ORF72 expansions, and the G4C2 repeat has also been reported in other motor phenotypes, such as primary lateral sclerosis, progressive muscular atrophy, corticobasal syndrome and Huntington-like disorders. In addition, the expansion has been identified in non-motor phenotypes including Alzheimer's disease and Lewy body dementia. It is not currently understood what is the basis of the clinical variation seen with the G4C2 repeat expansion. One potential explanation is repeat length. Sizing of the expansion by Southern blotting has established that there is somatic heterogeneity, with different expansion lengths in different tissues, even within the brain. To date, no correlation with expansion size and clinical phenotype has been established in ALS, whilst in FTLD only repeat size in the cerebellum was found to correlate with disease duration. Somatic heterogeneity suggests there is a degree of instability within the repeat and evidence of anticipation has been reported with reducing age of onset in subsequent generations. This variability/instability in expansion length, along with its interactions with environmental and genetic modifiers, such as TMEM106B, may be the basis of the differing clinical phenotypes arising from the mutation.
    Full-text · Article · Feb 2014 · Acta Neuropathologica
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    • "However, among families where both ALS and FTD cases are clustered together, strong linkage to chromosomal locus 9p21 was identified and defined as causative for the FTD/ALS spectrum [17] [18]. The associated risk haplotype has since been shown to be the same in all ALS and FTD populations studied, and is also present in affected members of several FTD/ALS families, suggesting a single founder mutation effect [19] "
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    ABSTRACT: Amyotrophic lateral sclerosis (ALS) is a progressive and lethal disease of motor neuron degeneration, leading to paralysis of voluntary muscles and death by respiratory failure within five years of onset. Frontotemporal dementia (FTD) is characterised by degeneration of frontal and temporal lobes, leading to changes in personality, behaviour, and language, culminating in death within 5-10 years. Both of these diseases form a clinical, pathological, and genetic continuum of diseases, and this link has become clearer recently with the discovery of a hexanucleotide repeat expansion in the C9orf72 gene that causes the FTD/ALS spectrum, that is, c9FTD/ALS. Two basic mechanisms have been proposed as being potentially responsible for c9FTD/ALS: loss-of-function of the protein encoded by this gene (associated with aberrant DNA methylation) and gain of function through the formation of RNA foci or protein aggregates. These diseases currently lack any cure or effective treatment. Antisense oligonucleotides (ASOs) are modified nucleic acids that are able to silence targeted mRNAs or perform splice modulation, and the fact that they have proved efficient in repeat expansion diseases including myotonic dystrophy type 1 makes them ideal candidates for c9FTD/ALS therapy. Here, we discuss potential mechanisms and challenges for developing oligonucleotide-based therapy for c9FTD/ALS.
    Full-text · Article · Nov 2013 · Journal of nucleic acids
    • "A custom PCR cycling program was used (4 min at 94°C; 50 cycles of 1 min at 94°C, 1 min at 64°C and 2 min at 72°C; 10 min at 72°C). Genotypes for the C9ORF72 risk haplotype SNPs (Mok et al., 2012a) were available for this analysis from a previous GWAS study (Edwards et al., 2010) for 10 out of 14 intermediate repeat copy carriers. For the remaining four, the haplotype tag rs3849942 was genotyped by Sanger sequencing. "
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    ABSTRACT: We set out to determine whether expansions in the C9ORF72 repeat found in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) families are associated with Parkinson disease (PD). We determined the repeat size in a total of 889 clinically ascertained patients (including PD and essential tremor plus Parkinsonism (ETP)) and 1144 controls using a repeat-primed PCR assay. We found that large C9ORF72 repeat expansions (>30 repeats) were not contributing to PD risk. However, PD and ETP cases had a significant increase in intermediate (>20 to 30+) repeat copies compared to controls. Overall, 14 cases (13 PD, 1 ETP) and three controls had >20 repeat copies (Fisher's exact test p = 0.002). Further, seven cases and no controls had >23 repeat copies (p = 0.003). Our results suggest that intermediate copy numbers of the C9ORF72 repeat contribute to risk for PD and ETP. This also suggests that PD, ALS and FTD share some pathophysiological mechanisms of disease. Further studies are needed to elucidate the contribution of the C9ORF72 repeat in the overall PD population and to determine whether other common genetic risk factors exist between these neurodegenerative disorders.
    No preview · Article · Jul 2013 · Annals of Human Genetics
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