Epigenetic Basis of Twin Discordance in Diseases: Future Benefits

Abstract

Monozygotic twins share the same genotype since they are derived from the same zygote. However,monozygotic twin siblings frequently present many phenotypic differences, such as their susceptibilitiesto diseases. These isogenic individuals are not entirely identical. They exhibit phenotypic incompatibilityfor many features, from birth weight to complex diseases. Recently, several studies have been publishedshowing that phenotypic differences, especially in monozygotic twins, are being induced from prenatalperiod to life-long epigenetic differences. Epigenetic studies on twins have a great potential to contributeto our understanding of complex diseases, such as cancer, autoimmune disorders, psychiatric disordersand neurological diseases. Since monozygotic twins are genetic clones (genetically identical), they areconsidered as perfect models for studying the role of environmental factors as determinants of complexdiseases and phenotypes. In this review, a number of intrauterine effects and genetic mechanisms thatmay affect phenotypic, genotypic, and epigenetic differences between monozygotic twins were describedand effects of epigenetic mechanisms on complex diseases were mentioned. Further work on epigeneticchanges in diseases using incompatible monozygotic twin models, would lead to new developments inmedical therapies.