A CpG Epigenetic Switch Reverts PFAS ToxicityAn In Vitro Study

Perfluorooctanesulfonic acid (PFOS) is a persistent environmental pollutant widely present in ecosystems and humans, linked to numerous diseases, including cancers, due to its potent toxicity. Despite its harmful effects, effective strategies for mitigating PFOS-induced toxicity remain undeveloped or at best underdeveloped. In this effort, we explore the concept of toxicity reversal by loci-specific DNA methylation editing to reverse PFOS-induced toxicity, whereby key cellular processes such as proliferation, migration, and apoptosis are restored. To demonstrate our concept, we employed CRISPR-dCas9 epigenome editing tools, utilizing catalytically deactivated Cas9 fused with either DNA methyltransferases or ten-eleven translocation (TET) dioxygenase effectors for loci-specific epigenome editing. Gene expression changes related to kidney disease, metabolism, and DNA methylation pathways were first noted. Through reduced representation bisulfite sequencing (RRBS), we demonstrated how PFOS exposure disrupts the epigenetic landscape, altering transcription factor binding sites linked to tumorigenesis, inflammation, and stress. By methylation editing of a single CpG site in implicated genes such as TARS2 and MAP2K5, we effectively reversed PFAS-induced toxicity and restored essential cell functions. Our success in precise single-CpG methylation editing of target genes effectively reverses toxicity, marking the first application of epigenome editing tools to counteract the toxic effects of a persistent environmental contaminant (PFAS). Our approach offers promising potential for toxicological screening and the identification of therapeutic targets to mitigate adverse effects triggered by environmental toxicants.