Exploring the extent and scope of epigenetic inheritance.

Environmental factors, particularly during early life, are important for the later metabolic health of the individual. In our obesogenic environment, it is of major socio-economic importance to investigate the mechanisms that contribute to the risk of metabolic ill health. Increasing evidence from a variety of model organisms suggests that non-genetically determined phenotypes, including metabolic effects such as glucose intolerance and obesity, can be passed between generations, which encourages us to revisit heredity. Inheritance of altered epigenetic information through the germ line has been proposed as one plausible mechanism. Whether the germline epigenome can be altered by environmental conditions such as diet and the extent to which this occurs in humans are the subject of intense current interest and debate, especially given that extensive germline epigenetic reprogramming is known to occur. As epigenetic mechanisms are often highly conserved between organisms, studying epigenetic inheritance in plants and lower metazoans has the potential to inform our investigation in mammals. This Review explores the extent to which epigenetic inheritance contributes to heredity in these different organisms, whether the environment can affect epigenetic inheritance and whether there is any evidence for the inheritance of acquired phenotypes.