<scp>CRISPR</scp>/<scp>C</scp>as9‐mediated gene knockout in the ascidian <i><scp>C</scp>iona intestinalis</i>

<jats:p>Knockout of genes with <jats:styled-content style="fixed-case">CRISPR</jats:styled-content>/<jats:styled-content style="fixed-case">C</jats:styled-content>as9 is a newly emerged approach to investigate functions of genes in various organisms. We demonstrate that <jats:styled-content style="fixed-case">CRISPR</jats:styled-content>/<jats:styled-content style="fixed-case">C</jats:styled-content>as9 can mutate endogenous genes of the ascidian <jats:italic><jats:styled-content style="fixed-case">C</jats:styled-content>iona intestinalis</jats:italic>, a splendid model for elucidating molecular mechanisms for constructing the chordate body plan. Short guide <jats:styled-content style="fixed-case">RNA</jats:styled-content> (sg<jats:styled-content style="fixed-case">RNA</jats:styled-content>) and <jats:styled-content style="fixed-case">C</jats:styled-content>as9 m<jats:styled-content style="fixed-case">RNA</jats:styled-content>, when they are expressed in <jats:italic><jats:styled-content style="fixed-case">C</jats:styled-content>iona</jats:italic> embryos by means of microinjection or electroporation of their expression vectors, introduced mutations in the target genes. The specificity of target choice by sg<jats:styled-content style="fixed-case">RNA</jats:styled-content> is relatively high compared to the reports from some other organisms, and a single nucleotide mutation at the sg<jats:styled-content style="fixed-case">RNA</jats:styled-content> dramatically reduced mutation efficiency at the on‐target site. <jats:styled-content style="fixed-case">CRISPR</jats:styled-content>/<jats:styled-content style="fixed-case">C</jats:styled-content>as9‐mediated mutagenesis will be a powerful method to study gene functions in <jats:italic><jats:styled-content style="fixed-case">C</jats:styled-content>iona</jats:italic> along with another genome editing approach using <jats:styled-content style="fixed-case">TALE</jats:styled-content> nucleases.</jats:p>