Transgenerational epigenetics: Integrating soma to germline communication with gametic inheritance.

Evidence supporting germline mediated epigenetic inheritance of environmentally induced traits has increasingly emerged over the past several years. Although the mechanisms underlying this inheritance remain unclear, recent findings suggest that parental gamete-borne epigenetic factors, particularly RNAs, affect post-fertilization and developmental gene regulation, ultimately leading to phenotypic appearance in the offspring. Complex processes involving gene expression and epigenetic regulation are considered to perpetuate across generations. In addition to transfer of germline factors, epigenetic inheritance via gametes also requires a mechanism whereby the information pertaining to the induced traits is communicated from soma to germline. Despite violating a century-old view in biology, this communication seems to play a role in transmission of environmental effects across generations. Circulating RNAs, especially those associated with extracellular vesicles like exosomes, are emerging as promising candidates that can transmit gene regulatory information in this direction. Cumulatively, these new observations provide a basis to integrate epigenetic inheritance. With significant implications in health, disease and ageing, the latter appears poised to revolutionize biology.