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MSH3 modifies somatic instability and disease severity in Huntington’s and myotonic dystrophy type 1
Journal article   Open access   Peer reviewed

MSH3 modifies somatic instability and disease severity in Huntington’s and myotonic dystrophy type 1

Michael Flower, Vilija Lomeikaite, Marc Ciosi, Sarah Cumming, Fernando Morales, Kitty Lo, Davina Hensman Moss, Lesley Jones, Peter Holmans, Darren G Monckton, …
Brain (London, England : 1878), Vol.142(7), pp.1876-1886
07/2019
DOI: 10.1093/brain/awz115
PMCID: PMC6598626
PMID: 31216018
url
https://doi.org/10.1093/brain/awz115View
Published (Version of record) Open Access

Abstract

A genome-wide association study recently identified an MSH3/DHFR locus associated with Huntington’s disease progression. Flower, Lomeikaite et al. identify tandem repeat variants at this locus, and show that a three-repeat allele is associated with reduced somatic expansion, delayed onset and slower progression in Huntington’s disease and myotonic dystrophy type 1. The mismatch repair gene MSH3 has been implicated as a genetic modifier of the CAG·CTG repeat expansion disorders Huntington’s disease and myotonic dystrophy type 1. A recent Huntington’s disease genome-wide association study found rs557874766, an imputed single nucleotide polymorphism located within a polymorphic 9 bp tandem repeat in MSH3 / DHFR , as the variant most significantly associated with progression in Huntington’s disease. Using Illumina sequencing in Huntington’s disease and myotonic dystrophy type 1 subjects, we show that rs557874766 is an alignment artefact, the minor allele for which corresponds to a three-repeat allele in MSH3 exon 1 that is associated with a reduced rate of somatic CAG·CTG expansion ( P = 0.004) and delayed disease onset ( P = 0.003) in both Huntington’s disease and myotonic dystrophy type 1, and slower progression ( P = 3.86 × 10 −7 ) in Huntington’s disease. RNA-Seq of whole blood in the Huntington’s disease subjects found that repeat variants are associated with MSH3 and DHFR expression. A transcriptome-wide association study in the Huntington’s disease cohort found increased MSH3 and DHFR expression are associated with disease progression. These results suggest that variation in the MSH3 exon 1 repeat region influences somatic expansion and disease phenotype in Huntington’s disease and myotonic dystrophy type 1, and suggests a common DNA repair mechanism operates in both repeat expansion diseases.
association study Huntington’s disease movement disorders myotonic dystrophy Reports transcriptomics

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