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As young adults, those not taking part in the second stage study (see below) have received a questionnaire representing the wave 4 follow-up of these twins.
This epidemiological first-stage of our FinnTwin12 study thus includes some 5,600 twins, and 5,000 of their biological parents, and, as expected from population-based ascertainment, the twins form equal proportions of brother-brother, sister-sister, and brother-sister pairs, permitting robust testing of gender modulation of genetic and environmental risks in the development of health behaviors, and appraisal of the magnitude and persistence of effects of variation in pubertal timing.
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We now have genome-wide genotyping data (‘gwas’) from the wave 4 twins genotyped on the Illumina 670 custom chip. This has been imputed to Hapmap2 and 1000 Genomes. In addition 200+ metabolites, primarily of lipids and their fractions have been determined from all twins, who provided blood samples (n=780) (Kettunen et al, Nature Genetics 2012) and cotinine, 3-hydroxycotinine and the nicotine metabolite ratio have been determined for smokers and their cotwins by professor Rachel Tyndale’s lab, University of Toronto for all occasional and daily smokers. We are currently completing the first epigenetic analyses using targeted gene-specific methylation assays, as well as genome-wide approaches (such as the Illumina Infinium 450k array). A small number of pairs have been invited to an intensive clinical assessment of metabolic health and obesity.
The FinnTwin12 dataset represents a very rich longitudinal design, with a genetically informative component (twins and parents). A recent overview has been published in by Rose R et al, in Twin Research and Human Genetics, 2019