A rare IL33 loss-of-function mutation reduces blood eosinophil counts and protects from asthma

Dirk Smith, Hannes Helgason, Patrick Sulem, Unnur Steina Bjornsdottir, Ai Ching Lim, Gardar Sveinbjornsson, Haruki Hasegawa, Michael Brown, Randal R Ketchem, Monica Gavala, Logan Garrett, Adalbjorg Jonasdottir, Aslaug Jonasdottir, Asgeir Sigurdsson, Olafur T Magnusson, Gudmundur I Eyjolfsson, Isleifur Olafsson, Pall Torfi Onundarson, Olof Sigurdardottir, David GislasonThorarinn Gislason, Bjorn Runar Ludviksson, Dora Ludviksdottir, H Marike Boezen, Andrea Heinzmann, Marcus Krueger, Celeste Porsbjerg, Tarunveer S Ahluwalia, Johannes Waage, Vibeke Backer, Klaus A Deichmann, Gerard H Koppelman, Klaus Bønnelykke, Hans Bisgaard, Gisli Masson, Unnur Thorsteinsdottir, Daniel F Gudbjartsson, James A Johnston, Ingileif Jonsdottir, Kari Stefansson

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Abstract

IL-33 is a tissue-derived cytokine that induces and amplifies eosinophilic inflammation and has emerged as a promising new drug target for asthma and allergic disease. Common variants at IL33 and IL1RL1, encoding the IL-33 receptor ST2, associate with eosinophil counts and asthma. Through whole-genome sequencing and imputation into the Icelandic population, we found a rare variant in IL33 (NM_001199640:exon7:c.487-1G>C (rs146597587-C), allele frequency = 0.65%) that disrupts a canonical splice acceptor site before the last coding exon. It is also found at low frequency in European populations. rs146597587-C associates with lower eosinophil counts (β = -0.21 SD, P = 2.5×10-16, N = 103,104), and reduced risk of asthma in Europeans (OR = 0.47; 95%CI: 0.32, 0.70, P = 1.8×10-4, N cases = 6,465, N controls = 302,977). Heterozygotes have about 40% lower total IL33 mRNA expression than non-carriers and allele-specific analysis based on RNA sequencing and phased genotypes shows that only 20% of the total expression is from the mutated chromosome. In half of those transcripts the mutation causes retention of the last intron, predicted to result in a premature stop codon that leads to truncation of 66 amino acids. The truncated IL-33 has normal intracellular localization but neither binds IL-33R/ST2 nor activates ST2-expressing cells. Together these data demonstrate that rs146597587-C is a loss of function mutation and support the hypothesis that IL-33 haploinsufficiency protects against asthma.

OriginalsprogEngelsk
Artikelnummere1006659
TidsskriftP L o S Genetics
Vol/bind13
Udgave nummer3
Antal sider24
ISSN1553-7390
DOI
StatusUdgivet - mar. 2017

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