PIWI-Interacting RNA (piRNA) and Epigenetic Editing in Environmental Health Sciences

PURPOSE OF REVIEW: The epigenome modulates gene expression in response to environmental stimuli. Modifications to the epigenome are potentially reversible, making them a promising therapeutic approach to mitigate environmental exposure effects on human health. This review details currently available genome and epigenome editing technologies and highlights ncRNA, including piRNA, as potential tools for targeted epigenome editing. RECENT FINDINGS: Zinc finger nuclease (ZFN), transcription activator-like effector nuclease (TALEN), and clustered regularly interspaced short palindromic repeats (CRISPR) associated nuclease (CRISPR/Cas) research has significantly advanced genome editing technology, with broad promise in genetic research and targeted therapies. Initial epigenome-directed therapies relied on global modification and suffered from limited specificity. Adapted from current genome editing tools, zinc finger protein (ZFP), TALE, and CRISPR/nuclease-deactivated Cas (dCas) systems now confer locus-specific epigenome editing, with promising applicability in the field of environmental health sciences. However, high incidence of off-target effects and time taken for screening limit their use. FUTURE DEVELOPMENT: ncRNA serve as a versatile biomarker with well-characterized regulatory mechanisms that can easily be adapted to edit the epigenome. For instance, the transposon silencing mechanism of germline PIWI-interacting RNAs (piRNA) could be engineered to specifically methylate a given gene, overcoming pitfalls of current global modifiers. Future developments in epigenome editing technologies will inform risk assessment through mechanistic investigation and serve as potential modes of intervention to mitigate environmentally induced adverse health outcomes later in life.