Poster Abstracts

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DNA methylation variants in young adult off spring exposed to famine during postnatal life in BangladeshS Finer, S Iqbal, C Mathews, B W Ogunkolade, M Smart, D Alam*, G Hitman*

Abstract Background Developmental programming via exposure to malnutrition suggests windows of susceptibility during periconceptual, in-utero, and postnatal periods, and might contribute to the missing heritability of complex disease. Metastable epialleles in off spring exposed to periconceptual nutritional defi ciency have been identifi ed, as have trimester-specifi c and sex-specifi c epigenetic eff ects. Methylation variation from postnatal exposure to famine has not been described. We aimed to identify whether Bangladeshi adults exposed to famine in utero or in postnatal life display DNA methylation variation compared with those unexposed, on a genome-wide scale or at previously described metastable epialleles.

Methods We studied a cross-sectional cohort of adults (27–32 years old) exposed to severe famine during 1974–75 in Matlab, Bangladesh. Whole blood DNA was bisulphite converted and hybridised to the Illumina 450k methylation array to access genome-wide DNA methylation. Normalised data were analysed with the limma package and methylation variable positions (MVPs) were identifi ed in two-way group comparisons (t test, leave-one-out cross-validation). Pathway analysis was done with GOstats. Replication of metastable epialleles was done with targeted bisulphite pyrosequencing. Samples were obtained with written consent, under ethics approval and a Material Transfer Agreement.

Findings 78 participants were included (25 exposed in utero, 29 exposed in postnatal life, and 24 unexposed). Samples from 55 individuals were used for validation. MVPs were identifi ed in the two-way comparisons of postnatal exposure versus unexposed (n=2122), and in-utero exposure versus unexposed (n=1454) but did not reach genome-wide signifi cance. Consistent directionality of methylation diff erence at MVPs in postnatal exposure versus unexposed was observed in validation samples (r²=0·69, p<0·05). Gene ontology analysis of MVPs suggests their role in growth factor signalling pathways. Preliminary analysis of targeted replication at metastable epialleles on all samples (n=133) showed methylation diff erences at PAX8 and ZFYVE28 across at least fi ve adjacent CpG sites according to in-utero and postnatal exposure.

Interpretation Our data identifi ed DNA methylation diff erences in young Bangladeshi adults exposed to famine in the postnatal period with putative roles in regulation of growth factor signalling. Preliminary replication using previously described metastable epialleles is reassuring, but requires further analysis. Larger sample sizes are required to control for multiple testing biases and false discovery. Future studies should incorporate the postnatal window of exposure, longitudinal sampling and intervention to establish causation over association, and primary aetiological over secondary pathophysiological epigenomic diff erences.

Funding UK Medical Research Council.

ContributorsDA and GH were responsible for the original cohort design. SF, DA, and GH designed the study. SF, SI, BWO, and MS did the experimental work. CM, SF, and GH analysed the data. SF and GH wrote the abstract.

Confl icts of interestWe declare that we have no confl icts of interest.

Published OnlineFebruary 26, 2014

Poster 37

*These authors contributed equally

Wellcome Trust MRC-Institute of Molecular

Science, University of Cambridge, Cambridge, UK

(S Finer PhD); ICDDR,B, Dhaka, Bangladesh (S Iqbal PhD,

Prof D Alam MD); and Blizard Institute, Barts and the

London, Queen Mary University of London, London,

UK (C Mathews MSc, W Ogunkolade PhD,

M Smart PhD, Prof G Hitman MD)

Correspondence to: Dr Sarah Finer, Wellcome

Trust-MRC Institute of Metabolic Science, University of Cambridge,

Wellcome Trust-MRC Institute of Metabolic Science,

Level 4, Box 289, Addenbrooke’s Hospital, Cambridge CB2 0QQ, UK

sf494@medschl.cam.ac.uk