Cas9 ribonucleoprotein complex allows direct and rapid analysis of coding and noncoding regions of target genes in Pleurodeles waltl development and regeneration

Newts have remarkable ability to regenerate their organs and have been used in research for centuries. However, the laborious work of breeding has hampered reverse genetics strategies in newt. Here, we present simple and efficient gene knockout using Cas9 ribonucleoprotein complex (RNP) in Pleurodeles waltl, a species suitable for regenerative biology studies using reverse genetics. Most of the founders exhibited severe phenotypes against each target gene (tyrosinase, pax6, tbx5); notably, all tyrosinase Cas9 RNP-injected embryos showed complete albinism. Moreover, amplicon sequencing analysis of Cas9 RNP-injected embryos revealed virtually complete biallelic disruption at target loci in founders, allowing direct phenotype analysis in the F0 generation. In addition, we demonstrated the generation of tyrosinase null F1 offspring within a year. Finally, we expanded this approach to the analysis of noncoding regulatory elements by targeting limb-specific enhancer of sonic hedgehog, known as the zone of polarizing activity regulatory sequence (ZRS; also called MFCS1). Disruption of ZRS led to digit deformation in limb regeneration. From these results, we are confident that this highly efficient gene knockout method will accelerate gene functional analysis in the post-genome era of salamanders. •Cas9-RNP targeted to tyr, pax6, and tbx5 caused severe phenotypes in founder newts.•Cas9-RNP injected founders are designated as crispants.•Crispants exhibited virtually complete biallelic disruption in targeted genes.•The first homozygous F1 offspring were obtained from tyr crispants within a year.•Disruption of shh limb-specific enhancer led to digit deformation in regeneration.