Chapter 9 - Heritable generational epigenetic effects through small noncoding RNA

Abstract

Transgenerational and intergenerational epigenetic effects are phenotypic differences inherited in the absence of alterations in the genome sequence from one generation to the next. They occur in a range of species, but the molecular mechanism underlying the observed inheritance patterns is often unclear. DNA methylation and chromatin structure are known to mediate epigenetic inheritance, and their inheritance mechanisms are well understood. Interestingly, studies of RNA interface pathways suggest that small RNAs also can mediate transgenerational epigenetic inheritance. For example, RNA can be directed to specific targets through base pairing with homologous sequence in RNA or DNA. Several classes of small RNA participate in epigenetic pathways, and mutant analyses link the small RNA pathways to various transgenerational and intergenerational epigenetic phenomena. In addition, inheritance of small RNA from the gametes to the zygote has been documented, and in Caenorhabditis elegans, small RNAs can mediate long-term inheritance of silencing phenotypes. This review explores the evidence in support of heritable generational effects mediated by small RNA and highlights gaps in knowledge that are the focus of on-going research.