Abstract
Non-coding RNAs (ncRNAs) are regulatory elements of gene expression and chromatin structure. Both long and small ncRNAs can also act as inductors and targets of epigenetic programs. Epigenetic patterns can be transmitted from one cell to the daughter cell, but, importantly, also through generations. Diversity of ncRNAs is emerging with new and surprising roles. Functional interactions among ncRNAs and between specific ncRNAs and structural elements of the chromatin are drawing a complex landscape. In this scenario, epigenetic changes induced by environmental stressors, including reprotoxicants, can explain some transgenerationally-transmitted phenotypes in non-Mendelian ways. In this review, we analyze mechanisms of action of reprotoxicants upon different types of ncRNAs and epigenetic modifications causing transgenerationally transmitted characters through germ cells but affecting germ cells and reproductive systems. A functional model of epigenetic mechanisms of transgenerational transmission ncRNAs-mediated is also proposed.
Highlights
The notion that most of the genome in the Eukaryota was “junk DNA” is already part of Biology history
Seminal works characterized the roles of some particular long non-coding RNAs. This is the case of the Xist gene that participates, by epigenetic mechanisms, in the inactivation of one X chromosome in females or the X chromosome in spermatogenesis [8,9,10,11], or other lncRNAs involved in genomic imprinting [12]
This landscape indicates that methylation and associated mechanisms are dynamic processes able to be adapted to specific requirements of development and potentially to the changes in the environment, especially in early embryonic stages and germ cell differentiation, including stress induced by reprotoxicants
Summary
The notion that most of the genome in the Eukaryota was “junk DNA” is already part of Biology history. The complexity of all functional variants is enhanced by the diversity of cell types and developmental periods and mediated by environmental mechanisms At present, both small and long non-coding RNAs are considered key elements in the fine regulatory mechanisms of gene expression and function. The changes in the genome expression modulated by environmental conditions are mediated by epigenetic mechanisms able to induce alterations in gene expression with phenotypic effects in individuals exposed, and with the possibility of transmission to successive generations [14] Reprotoxicants are considered those toxicants that in someway affect reproductive systems of the organisms. We will review different mechanisms of epigenetic transmission environmentally induced, focusing on the role of different non-coding RNAs in the alteration of germ cells differentiation and reproductive systems development, caused by the exposure of environmental pollutants, which by epigenetic mechanisms could be transmitted to successive generations
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