The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system naturally occurs in prokaryotic organisms (archaea and bacteria), serving as a defense mechanism against attacking viruses and plasmids. The system is based on complementary RNA-guided cleavage of the target (foreign) DNA, marking it for subsequent degradation. In eukaryotes, which possess sophisticated DNA repair mechanisms, the cleaved DNA is repaired via one of two mechanisms: non-homologous end-joining (error-prone) or homologous directed DNA (template-dependent). Compared with other gene editing tools that have been developed over the years, CRISPR-Cas9 is cost-effective, extremely precise, and reliable, offering robust and high throughput genetic engineering. This book outlines the application of CRISPR-Cas9 in human health, agriculture, genetic engineering, and environmental sciences.

CRISPR-Cas9-mediated genome engineering has revolutionized biomedical research. It is widely used in the development of novel approaches to treat cancer, chronic diseases, infectious diseases, and congenital defects. In this book, we review the latest advances in the clinical applications of CRISPR-Cas9, including those for the correction of loss-of-function and gain-of-function-mutations responsible for genetic and neuromuscular diseases. We also explore the emerging applications of CRISPR-Cas9 in the diagnosis and treatment of infectious diseases caused by bacteria, protozoa, and viruses. We pay particular attention to the use of CRISPR-Cas9 in the identification of cancer-related genes, novel drug targets, and biomarkers in cancer. Lastly, we summarize the emerging applications of CRISPR-Cas9 technology in tissue and organ regeneration.