Conditional knockouts generated by engineered CRISPR-Cas9 endonuclease reveal the roles of coronin in C. elegans neural development.

Conditional gene knockout animals are valuable tools for studying the mechanisms underlying cell and developmental biology. We developed a conditional knockout strategy by spatiotemporally manipulating the expression of an RNA-guided DNA endonuclease, CRISPR-Cas9, in Caenorhabditis elegans somatic cell lineages. We showed that this somatic CRISPR-Cas9 technology provides a quick and efficient approach to generate conditional knockouts in various cell types at different developmental stages. Furthermore, we demonstrated that this method outperforms our recently developed somatic TALEN technique and enables the one-step generation of multiple conditional knockouts. By combining these techniques with live-cell imaging, we showed that an essential embryonic gene, Coronin, which is associated with human neurobehavioral dysfunction, regulates actin organization and cell morphology during C. elegans postembryonic neuroblast migration and neuritogenesis. We propose that the somatic CRISPR-Cas9 platform is uniquely suited for conditional gene editing-based biomedical research.