Chapter 10 - Heritable Generational Epigenetic Effects through RNA

Abstract

Heritable transgenerational epigenetic effects are observed in many species, where they are detected as phenotypic differences inherited in the absence of alterations in the genome sequence. Despite their widespread nature, the molecular mechanism underlying the observed inheritance patterns is often not understood. DNA methylation and chromatin structure (histone modifications) are known to mediate transgenerational epigenetic inheritance. Recent studies of the various small RNA silencing pathways suggest that RNA should also be considered a candidate mechanism for transgenerational epigenetic inheritance. RNA is a very attractive candidate molecule because it potentially has targeting ability through base pairing with homologous sequences in other RNAs or DNA. Several classes of small RNAs participate in epigenetic pathways, and mutant analyses link the small RNA pathways to several transgenerational epigenetic phenomena. In addition, RNAs of various kinds are present in the gametes, indicating that they may be transmitted to the zygote. This review explores the evidence in support of heritable generational effects mediated by RNA.