Transgenerational inheritance: Models and mechanisms of non–DNA sequence–based inheritance

Heritability has traditionally been thought to be a characteristic feature of the genetic material of an organism—notably, its DNA. However, it is now clear that inheritance not based on DNA sequence exists in multiple organisms, with examples found in microbes, plants, and invertebrate and vertebrate animals. In mammals, the molecular mechanisms have been challenging to elucidate, in part due to difficulties in designing robust models and approaches. Here we review some of the evidence, concepts, and potential mechanisms of non–DNA sequence–based transgenerational inheritance. We highlight model systems and discuss whether phenotypes are replicated or reconstructed over successive generations, as well as whether mechanisms operate at transcriptional and/or posttranscriptional levels. Finally, we explore the short- and long-term implications of non–DNA sequence–based inheritance. Understanding the effects of non–DNA sequence–based mechanisms is key to a full appreciation of heritability in health and disease.