Generational stability of epigenetic transgenerational inheritance facilitates adaptation and evolution

Abstract

The epigenome and epigenetic inheritance were not included in the original modern synthesis theory or more recent extended evolutionary synthesis of evolution. In a broad range of species, the environment has been shown to play a significant role in natural selection, which more recently has been shown to occur through epigenetic alterations and epigenetic inheritance. However, even with this evidence, the field of epigenetics and epigenetic inheritance has been left out of modern evolutionary synthesis, as well as other current evolutionary models. Epigenetic mechanisms can direct the regulation of genetic processes (e.g. gene expression) and also can be directly changed by the environment. In contrast, DNA sequence cannot be directly altered by the environment. The goal of this review is to present the evidence of how epigenetics and epigenetic inheritance can alter phenotypic variation in numerous species. This can occur at a significantly higher frequency than genetic change, so correlates with the frequency of evolutionary change. In addition, the concept and importance of generational stability of transgenerational inheritance is incorporated into evolutionary theory. For there to be a better understanding of evolutionary biology, we must incorporate all aspects of molecular (e.g. genetics and epigenetics) and biological sciences (e.g. environment and adaptation).

Keywords: Epigenetic; adaptation; evolutionary biology; generational stability; inheritance; review; transgenerational.

Figure 1.

Unified theory of evolution with incorporation of epigenetics and epigenetic transgenerational inheritance. Inclusion of both darwinian concepts and neo-lamarckian concepts to expand evolutionary theory. Schematic of the unified theory of evolution. No dominance is suggested by the appearance of specific circles (e.g., epimutations versus genetics) such that all are equally important components. Modified from Skinner [16].

Figure 2.

Schematic of epigenetic processes. Representation of the primary epigenetic factors and processes schematic of non-coding RNA, DNA methylation, chromatin structure, histone modifications, and DNA structure presented. Modified from Nilsson, et al. [21].

Figure 3.

Clarification of intergenerational and transgenerational epigenetic inheritance. Environmentally induced transgenerational epigenetic inheritance: schematic of environmental exposure and affected generations for both gestating female and adult male or female. The multigenerational direct exposures are indicated in contrast to the transgenerational generation without direct exposure. Modified from Nilsson, et al. [21].

Figure 4.

Environmentally induced epigenetic transgenerational inheritance and generational toxicology. A variety of toxicants and exposures are listed that promote epigenetic transgenerational inheritance. A number of different organisms the environmental exposure promotes epigenetic transgenerational inheritance are presented, from plants to humans. Modified from Nilsson, et al. [21].