Determining the biological mechanisms of action for environmental exposures: Applying CRISPR/Cas9 to toxicological assessments

Toxicology is a constantly evolving field, especially in the area of developing alternatives to animal testing. Toxicological research must evolve and utilize adaptive technologies in an effort to improve public, environmental, and occupational health. The most commonly cited mechanisms of toxic action after exposure to a chemical or particle test substance is oxidative stress. However, because oxidative stress involves a plethora of genes and proteins, the exact mechanism(s) are not commonly defined. Exact mechanisms of toxicity can be revealed using an emerging laboratory technique referred to as CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats). This paper reviews the most common CRISPR techniques utilized today and how each may be applied in toxicological science. Specifically, the CRISPR/CRISPR-associated (Cas) protein complex is used for single gene knock-outs, while CRISPR interference/activation (CRISPRi/CRISPRa) is used for silencing or activating (respectively) ribonucleic acid (RNA). Finally, CRISPR libraries are used for knocking-out entire gene pathways. This review highlights the application of CRISPR in toxicology to elucidate the exact mechanism through which toxicants perturb normal cellular functions.