Ciosi, Marc, Maxwell, Alastair, Cumming, Sarah, Hensman Moss, Davina, Alshammari, Asma, Flower, Michael, Durr, Alexandra, Leavitt, Blair, Roos, Raymund, Holmans, Peter ORCID: https://orcid.org/0000-0003-0870-9412, Jones, Lesley ORCID: https://orcid.org/0000-0002-3007-4612, Langbehn, Douglas, Kwak, Seung, Tabrizi, Sarah and Monckton, Darren 2019. A genetic association study of glutamine-encoding DNA sequence structures, somatic CAG expansion, and DNA repair gene variants, with Huntington disease clinical outcomes. EBioMedicine 48 , pp. 568-580. 10.1016/j.ebiom.2019.09.020 |
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Abstract
Background: Huntington disease (HD) is caused by an unstable CAG/CAA repeat expansion encoding a toxic polyglutamine tract. Here, we tested the hypotheses that HD outcomes are impacted by somatic expansion of, and polymorphisms within, the HTT CAG/CAA glutamine-encoding repeat, and DNA repair genes. Methods: The sequence of the glutamine-encoding repeat and the proportion of somatic CAG expansions in blood DNA from participants inheriting 40 to 50 CAG repeats within the TRACK-HD and Enroll-HD cohorts were determined using high-throughput ultra-deep-sequencing. Candidate gene polymorphisms were genotyped using kompetitive allele-specific PCR (KASP). Genotypic associations were assessed using time-to-event and regression analyses. Findings: Using data from 203 TRACK-HD and 531 Enroll-HD participants, we show that individuals with higher blood DNA somatic CAG repeat expansion scores have worse HD outcomes: a one-unit increase in somatic expansion score was associated with a Cox hazard ratio for motor onset of 3·05 (95% CI = 1·94 to 4·80, p = 1·3 × 10−6). We also show that individual-specific somatic expansion scores are associated with variants in FAN1 (pFDR = 4·8 × 10-6), MLH3 (pFDR = 8·0 × 10−4), MLH1 (pFDR = 0·004) and MSH3 (pFDR = 0·009). We also show that HD outcomes are best predicted by the number of pure CAGs rather than total encoded-glutamines. Interpretation: These data establish pure CAG length, rather than encoded-glutamine, as the key inherited determinant of downstream pathophysiology. These findings have implications for HD diagnostics, and support somatic expansion as a mechanistic link for genetic modifiers of clinical outcomes, a driver of disease, and potential therapeutic target in HD and related repeat expansion disorders.
Item Type: | Article |
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Date Type: | Publication |
Status: | Published |
Schools: | Medicine MRC Centre for Neuropsychiatric Genetics and Genomics (CNGG) |
Publisher: | Elsevier |
ISSN: | 2352-3964 |
Funders: | MRC |
Date of First Compliant Deposit: | 16 September 2019 |
Date of Acceptance: | 11 September 2019 |
Last Modified: | 22 Nov 2024 05:45 |
URI: | https://orca.cardiff.ac.uk/id/eprint/125434 |
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