Efficient RNA/Cas9-mediated genome editing in Xenopus tropicalis

Area of Science:

• Amphibian genetics
• Genome editing technologies
• Molecular biology

Background:

• Targeted gene disruption in Xenopus tropicalis traditionally relies on zinc-finger nucleases (ZFNs) or transcription activator-like effector nucleases (TALENs).
• These existing methods require complex design, selection, or laborious construction, highlighting the need for simpler, more efficient tools.

Purpose of the Study:

• To evaluate the efficacy and reliability of the RNA-guided Cas9 nuclease system for genome editing in Xenopus tropicalis.
• To demonstrate the potential of Cas9 for multiplexed genome engineering and phenotypic assessment in Xenopus embryos.

Main Methods:

• Utilized RNA-guided Cas9 nuclease for targeted gene disruption across ten different genes in Xenopus tropicalis.
• Performed systematic point mutation analyses to determine optimal conditions for Cas9 cleavage.
• Applied Cas9 for multiplexed genome engineering and assessed gene disruption in specific genes (ptf1a/p48, tyrosinase).
• Analyzed the transmission of targeted mutations to the F1 generation in founder frogs.

Main Results:

• Achieved precise targeted gene disruption in all ten analyzed Xenopus tropicalis genes with efficiencies ranging from 45% to 100%.
• Confirmed that perfect matches between spacer and protospacer sequences adjacent to the protospacer adjacent motif (PAM) are crucial for Cas9 activity.
• Demonstrated successful multiplexed genome engineering and facilitated direct phenotypic assessment via Cas9-mediated gene disruption.
• Observed highly efficient transmission of targeted mutations to F1 embryos from founder frogs.

Conclusions:

• The Cas9 system offers an easy, efficient, and reliable method for multiplex genome editing in Xenopus tropicalis.
• This tool significantly advances genetic research capabilities in this amphibian model.
• Cas9-mediated gene targeting facilitates straightforward phenotypic analysis in Xenopus embryos.