Epigenetics refers to the heritable, but reversible, regulation of genes that is controlled by chemical attachments to DNA and chromosome proteins. Inherited and acquired epigenetic misregulation is consistent with numerous disease features. In type 1 diabetes (T1D), epigenetic mechanisms can explain why 35% of monozygotic twins exhibit differential susceptibility to T1D, i.e. only one twin is affected and his/her co-twin stays healthy despite their identical DNA sequences and similar environmental exposure. Differences in the incidence of T1D between males and females could also be of epigenetic origin. In a similar way, the observation that men with T1D are more likely to transmit the disease to their offspring than their female counterparts may be the result of epigenetic differences in the maternal genes vs. paternal genes. To date, however, few studies have investigated the role of epigenetic factors in T1D, and none have utilized an epigenome-wide approach. This project is dedicated to the comprehensive epigenomic analysis of T1D. More specifically, we will investigate DNA methylation, which is one of the key epigenetic mechanisms. The main goal of this project is to identify DNA methylation alterations, or epimutations, that cause or predispose individuals to T1D.
Our first aim i s to uncover DNA methylation changes that lead to misregulation of the insulin gene in the thymus. The rationale for this study is based on the observation that if there is not enough insulin in the thymus during embryogenesis, immune cells that produce antibodies against insulin will stay alive. Later in life, such cells may attack pancreatic cells that synthesize insulin, and this will result in T1D. We hypothesize that lack of insulin in the thymus is, to some extent, due to epigenetic misregulation of the insulin gene. Our effort will be dedicated to a detailed DNA methylation analysis of several million nucleotides that surround the insulin gene. The detected DNA methylation factors that account for low activity of the insulin gene will be tested in large samples of T1D patients and control individuals.
Our second aim i s to perform whole DNA methylome studies in peripheral blood samples from pairs of twins and non-twin siblings where only one of the twins or siblings is affected with T1D. To identify which epigenetic changes were inherited and which ones were acquired later in life, we will test germline samples of fathers who have children with T1D and are also affected with T1D themselves or have a family history of T1D. DNA methylation patterns will be investigated in over 1,000 DNA samples from individuals with T1D and their unaffected relatives. The project should help us understand the molecular basis of T1D. The identification of epigenetic disease markers would be of critical importance in the diagnostic, treatment, and prophylactic applications in T1D.
Project Narrative There is increasing theoretical and experimental evidence that epigenetic misregulation may be involved in the etiopathogenesis of type 1 diabetes (T1D). In this project, we plan to perform a very large scale epigenome study of T1D, which may uncover the molecular mechanisms by which genes become disregulated and predispose to T1D. This effort may have a major impact on our understanding of autoimmune mechanisms in T1D and lead to new strategies in diagnostics and treatment of the disease.
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