Screening for C9orf72 repeat expansions in parkinsonian syndromes.
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ABSTRACT:
SUBMITTER: Yeh TH
PROVIDER: S-EPMC4022748 | biostudies-literature | 2013 Apr
REPOSITORIES: biostudies-literature
Publications
Screening for C9orf72 repeat expansions in parkinsonian syndromes.
Yeh Tu-Hsueh TH Lai Szu-Chia SC Weng Yi-Hsin YH Kuo Hung-Chou HC Wu-Chou Yah-Huei YH Huang Chia-Ling CL Chen Rou-Shayn RS Chang Hsiu-Chen HC Traynor Bryan B Lu Chin-Song CS
Neurobiology of aging 20121011 4
Parkinsonism might precede, coincide, or follow the behavioral or language-predominant cognitive impairments characteristic of frontotemporal dementia (FTD). In this study, we analyze the hexanucleotide repeat expansions within C9orf72 gene in various parkinsonian syndromes because it is a recently identified important genetic cause of FTD. The expanded hexanucleotide repeat is only identified in our familial FTD patients but not in patients with predominant parkinsonism. The lack of association ...[more]
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Project description:IMPORTANCE:Hexanucleotide repeat expansions in the chromosome 9 open reading frame 72 (C9orf72) gene underlie a significant fraction of frontotemporal dementia and amyotrophic lateral sclerosis. OBJECTIVE:To investigate the frequency of C9orf72 repeat expansions in clinically diagnosed late-onset Alzheimer disease (AD). DESIGN, SETTING, AND PATIENTS:This case-control study genotyped the C9orf72 repeat expansion in 872 unrelated familial AD cases and 888 control subjects recruited as part of the National Institute on Aging Late-Onset Alzheimer Disease Family Study cohort, a multisite collaboration studying 1000 families with 2 or more individuals clinically diagnosed as having late-onset AD. MAIN OUTCOMES AND MEASURES:We determined the presence or absence of the C9orf72 repeat expansion by repeat-primed polymerase chain reaction, the length of the longest nonexpanded allele, segregation of the genotype with disease, and clinical features of repeat expansion carriers. RESULTS Three families showed large C9orf72 hexanucleotide repeat expansions. Two additional families carried more than 30 repeats. Segregation with disease could be demonstrated in 3 families. One affected expansion carrier had neuropathology compatible with AD. In the National Institute on Aging Late-Onset Alzheimer Disease Family Study series, the C9orf72 repeat expansions constituted the second most common pathogenic mutation, just behind the PSEN1 A79V mutation, highlighting the heterogeneity of clinical presentations associated with repeat expansions. CONCLUSIONS AND RELEVANCE:C9orf72 repeat expansions explain a small proportion of patients with a clinical presentation indistinguishable from AD, and they highlight the necessity of screening frontotemporal dementia genes in clinical AD cases with strong family history.
| S-EPMC3681841 | biostudies-literature
Project description:Hexanucleotide expansions in the C9ORF72 gene are frequently found in patients with amyotrophic lateral sclerosis, frontotemporal dementia or both, some of whom exhibit concurrent extrapyramidal symptoms. To determine if repeat expansions are a cause of Parkinson's disease (PD), we used repeat-primed polymerase chain reaction to investigate the frequency of C9ORF72 repeat expansions in a cohort of 478 patients with PD and 662 control subjects. Three control subjects were found to be expansion carriers, and no expansions were found among patients, suggesting that C9ORF72 expansions are not a common cause of PD.
| S-EPMC3566343 | biostudies-literature
Project description:The loss of chromosome 9 open reading frame 72 (C9ORF72) expression, associated with C9ORF72 repeat expansions, has not been examined systematically. Three C9ORF72 transcript variants have been described thus far; the GGGGCC repeat is located between two non-coding exons (exon 1a and exon 1b) in the promoter region of transcript variant 2 (NM_018325.4) or in the first intron of variant 1 (NM_145005.6) and variant 3 (NM_001256054.2). We studied C9ORF72 expression in expansion carriers (n = 56) for whom cerebellum and/or frontal cortex was available. Using quantitative real-time PCR and digital molecular barcoding techniques, we assessed total C9ORF72 transcripts, variant 1, variant 2, variant 3, and intron containing transcripts [upstream of the expansion (intron 1a) and downstream of the expansion (intron 1b)]; the latter were correlated with levels of poly(GP) and poly(GA) proteins aberrantly translated from the expansion as measured by immunoassay (n = 50). We detected a decrease in expansion carriers as compared to controls for total C9ORF72 transcripts, variant 1, and variant 2: the strongest association was observed for variant 2 (quantitative real-time PCR cerebellum: median 43 %, p = 1.26e-06, and frontal cortex: median 58 %, p = 1.11e-05; digital molecular barcoding cerebellum: median 31 %, p = 5.23e-10, and frontal cortex: median 53 %, p = 5.07e-10). Importantly, we revealed that variant 1 levels greater than the 25th percentile conferred a survival advantage [digital molecular barcoding cerebellum: hazard ratio (HR) 0.31, p = 0.003, and frontal cortex: HR 0.23, p = 0.0001]. When focusing on intron containing transcripts, analysis of the frontal cortex revealed an increase of potentially truncated transcripts in expansion carriers as compared to controls [digital molecular barcoding frontal cortex (intron 1a): median 272 %, p = 0.003], with the highest levels in patients pathologically diagnosed with frontotemporal lobar degeneration. In the cerebellum, our analysis suggested that transcripts were less likely to be truncated and, excitingly, we discovered that intron containing transcripts were associated with poly(GP) levels [digital molecular barcoding cerebellum (intron 1a): r = 0.33, p = 0.02, and (intron 1b): r = 0.49, p = 0.0004] and poly(GA) levels [digital molecular barcoding cerebellum (intron 1a): r = 0.34, p = 0.02, and (intron 1b): r = 0.38, p = 0.007]. In summary, we report decreased expression of specific C9ORF72 transcripts and provide support for the presence of truncated transcripts as well as pre-mRNAs that may serve as templates for RAN translation. We further show that higher C9ORF72 levels may have beneficial effects, which warrants caution in the development of new therapeutic approaches.
| S-EPMC4655160 | biostudies-literature
Project description:ObjectiveTo identify potential genetic modifiers contributing to the phenotypic variability that is detected in patients with repeat expansions in chromosome 9 open reading frame 72 (C9ORF72), we investigated the frequency of these expansions in a cohort of 334 subjects previously found to carry mutations in genes known to be associated with a spectrum of neurodegenerative diseases.MethodsA 2-step protocol, with a fluorescent PCR and a repeat-primed PCR, was used to determine the presence of hexanucleotide expansions in C9ORF72. For one double mutant, we performed Southern blots to assess expansion sizes, and immunohistochemistry to characterize neuropathology.ResultsWe detected C9ORF72 repeat expansions in 4 of 334 subjects (1.2% [or 1.8% of 217 families]). All these subjects had behavioral phenotypes and also harbored well-known pathogenic mutations in either progranulin (GRN: p.C466LfsX46, p.R493X, p.C31LfsX35) or microtubule-associated protein tau (MAPT: p.P301L). Southern blotting of one double mutant with a p.C466LfsX46 GRN mutation demonstrated a long repeat expansion in brain (>3,000 repeats), and immunohistochemistry showed mixed neuropathology with characteristics of both C9ORF72 expansions and GRN mutations.ConclusionsOur findings indicate that co-occurrence of 2 evidently pathogenic mutations could contribute to the pleiotropy that is detected in patients with C9ORF72 repeat expansions. These findings suggest that patients with known mutations should not be excluded from further studies, and that genetic counselors should be aware of this phenomenon when advising patients and their family members.
| S-EPMC3806926 | biostudies-literature
Project description:The hexanucleotide repeat expansion in the C9orf72 gene is the most common genetic variant found in individuals with sporadic amyotrophic lateral sclerosis (ALS), occurring at a frequency of between 7 and 11% in cohorts of European ancestry. While limited data suggest that C9-expansions (>30 repeats) are less frequent in African-Americans with ALS, there is no data on the frequency of C9-expansions among ALS subjects residing in Africa. We therefore investigated the frequency of this expansion mutation (using repeat-primed PCR) in a cohort of 143 South Africans (SA) with ALS. The cohort included different genetic ancestry subgroups who self-identified as black African (n = 24), Cape mixed-African (M/A) (n = 65), white European ancestry (n = 51), and Indian ancestry (n = 3). Three M/A individuals had a family history of ALS (2%) and all had normal C9orf72 alleles. Of the 140 individuals with sporadic ALS who were successfully genotyped, 10 (7%) carried pathogenic C9-expansions; four white and six M/A ancestry individuals, respectively. Our results highlight the importance of including Africans in genetic studies aimed at unravelling the genomic architecture in ALS and suggest pathogenetic mechanisms other than the C9orf72 expansion in black Africans with ALS.
| S-EPMC6556408 | biostudies-literature
Project description:Due to the GC-rich, repetitive nature of C9orf72 hexanucleotide repeat expansions, PCR based detection methods are challenging. Several limitations of PCR have been reported and overcoming these could help to define the pathogenic range. There is also a need to develop improved repeat-primed PCR assays which allow detection even in the presence of genomic variation around the repeat region. We have optimised PCR conditions for the C9orf72 hexanucleotide repeat expansion, using betaine as a co-solvent and specific cycling conditions, including slow ramping and a high denaturation temperature. We have developed a flanking assay, and repeat-primed PCR assays for both 3' and 5' ends of the repeat expansion, which when used together provide a robust strategy for detecting the presence or absence of expansions greater than ∼100 repeats, even in the presence of genomic variability at the 3' end of the repeat. Using our assays, we have detected repeat expansions in 47/442 Scottish ALS patients. Furthermore, we recommend the combined use of these assays in a clinical diagnostic setting.
| S-EPMC4978699 | biostudies-literature
Project description:It has been recently reported that a large proportion of patients with familial amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are associated with a hexanucleotide (GGGGCC) repeat expansion in the first intron of C9ORF72. We have assessed 1757 Italian sporadic ALS cases, 133 from Sardinia, 101 from Sicily, and 1523 from mainland Italy. Sixty (3.7%) of 1624 mainland Italians and Sicilians and 9 (6.8%) of the 133 Sardinian sporadic ALS cases carried the pathogenic repeat expansion. None of the 619 regionally matched control samples (1238 chromosomes) carried the expansion. Twenty-five cases (36.2%) had behavioral FTD in addition to ALS. FTD or unspecified dementia was also detected in 19 pedigrees (27.5%) in first-degree relatives of ALS patients. Cases carrying the C9ORF72 hexanucleotide expansion survived 1 year less than cases who did not carry this mutation. In conclusion, we found that C9ORF72 hexanucleotide repeat expansions represents a sizeable proportion of apparent sporadic ALS in the Italian and Sardinian population, representing by far the most common mutation in Italy and the second most common in Sardinia.
| S-EPMC3372681 | biostudies-literature
Project description:Hexanucleotide repeat expansions in C9orf72 are a major cause of frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). Understanding the disease mechanisms and a method for clinical diagnostic genotyping have been hindered because of the difficulty in estimating the expansion size. We found 96 repeat-primed PCR expansions: 85/2,974 in six neurodegenerative diseases cohorts (FTLD, ALS, Alzheimer disease, sporadic Creutzfeldt-Jakob disease, Huntington disease-like syndrome, and other nonspecific neurodegenerative disease syndromes) and 11/7,579 (0.15%) in UK 1958 birth cohort (58BC) controls. With the use of a modified Southern blot method, the estimated expansion range (smear maxima) in cases was 800-4,400. Similarly, large expansions were detected in the population controls. Differences in expansion size and morphology were detected between DNA samples from tissue and cell lines. Of those in whom repeat-primed PCR detected expansions, 68/69 were confirmed by blotting, which was specific for greater than 275 repeats. We found that morphology in the expansion smear varied among different individuals and among different brain regions in the same individual. Expansion size correlated with age at clinical onset but did not differ between diagnostic groups. Evidence of instability of repeat size in control families, as well as neighboring SNP and microsatellite analyses, support multiple expansion events on the same haplotype background. Our method of estimating the size of large expansions has potential clinical utility. C9orf72-related disease might mimic several neurodegenerative disorders and, with potentially 90,000 carriers in the United Kingdom, is more common than previously realized.
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Project description:An expanded GGGGCC repeat in C9orf72 is the most common genetic cause of frontotemporal dementia and amyotrophic lateral sclerosis. A fundamental question is whether toxicity is driven by the repeat RNA itself and/or by dipeptide repeat proteins generated by repeat-associated, non-ATG translation. To address this question, we developed in vitro and in vivo models to dissect repeat RNA and dipeptide repeat protein toxicity. Expression of pure repeats, but not stop codon-interrupted "RNA-only" repeats in Drosophila caused adult-onset neurodegeneration. Thus, expanded repeats promoted neurodegeneration through dipeptide repeat proteins. Expression of individual dipeptide repeat proteins with a non-GGGGCC RNA sequence revealed that both poly-(glycine-arginine) and poly-(proline-arginine) proteins caused neurodegeneration. These findings are consistent with a dual toxicity mechanism, whereby both arginine-rich proteins and repeat RNA contribute to C9orf72-mediated neurodegeneration.
| S-EPMC4944841 | biostudies-literature
Project description:Multiple system atrophy (MSA) is a fatal neurodegenerative disorder of unknown etiology that presents with variable combinations of progressive ataxia, parkinsonism, and autonomic instability. Pathologic expansion of a hexanucleotide repeat in the C9orf72 gene has been demonstrated to cause neurodegeneration with diverse neurologic presentations. To test the hypothesis whether pathologic expansions in C9orf72 are a cause of MSA, we undertook genetic screening in 100 neuropathologically confirmed cases. No pathologic repeat expansions were detected suggesting that MSA is not a C9orf72-related neurodegenerative disease.
| S-EPMC4315721 | biostudies-literature