1. Sequence variations in C9orf72 downstream of the hexanucleotide repeat region and its effect on repeat-primed PCR interpretation: a large multinational screening study.
- Author
-
Nordin A, Akimoto C, Wuolikainen A, Alstermark H, Forsberg K, Baumann P, Pinto S, de Carvalho M, Hübers A, Nordin F, Ludolph AC, Weishaupt JH, Meyer T, Grehl T, Schweikert K, Weber M, Burkhardt C, Neuwirth C, Holmøy T, Morita M, Tysnes OB, Benatar M, Wuu J, Lange DJ, Bisgård C, Asgari N, Tarvainen I, Brännström T, and Andersen PM
- Subjects
- Adolescent, Adult, Age of Onset, Aged, Aged, 80 and over, Amyotrophic Lateral Sclerosis epidemiology, Base Sequence, Cohort Studies, DNA Repeat Expansion, Female, Frontotemporal Dementia genetics, Gene Frequency, Genetic Predisposition to Disease, Genetic Variation, Humans, Male, Middle Aged, Polymerase Chain Reaction, Survival Analysis, Young Adult, Amyotrophic Lateral Sclerosis genetics, C9orf72 Protein genetics
- Abstract
A large GGGGCC-repeat expansion mutation (HREM) in C9orf72 is the most common known cause of ALS and FTD in European populations. Sequence variations immediately downstream of the HREM region have previously been observed and have been suggested to be one reason for difficulties in interpreting RP-PCR data. Our objective was to determine the properties of these sequence variations with regard to prevalence, the range of variation, and effect on disease prognosis. We screened a multi-national cohort (n = 6981) for the HREM and samples with deviant RP-PCR curves were identified. The deviant samples were subsequently sequenced to determine sequence alteration. Our results show that in the USA and European cohorts (n = 6508) 10.7% carried the HREM and 3% had a sequence variant, while no HREM or sequence variants were observed in the Japanese cohort (n = 473). Sequence variations were more common on HREM alleles; however, certain population specific variants were associated with a non-expanded allele.In conclusion, we identified 38 different sequence variants, most located within the first 50 bp downstream of the HREM region. Furthermore, the presence of an HREM was found to be coupled to a lower age of onset and a shorter disease survival, while sequence variation did not have any correlation with these parameters.
- Published
- 2017
- Full Text
- View/download PDF