Comparison Between Electroporation at Different Voltage Levels and Microinjection to Generate Porcine Embryos with Multiple Xenoantigen Knock-Outs

Abstract

In the context of xenotransplantation, the production of genetically modified pigs is essential. For several years, knock-out pigs were generated through somatic cell nuclear transfer employing donor cells with the desired genetic modifications, which resulted in a lengthy and cumbersome procedure. The CRISPR/Cas9 system enables direct targeting of specific genes in zygotes directly through microinjection or electroporation. However, these techniques require improvement to minimize mosaicism and low mutation rates without compromising embryo survival. This study aimed to determine the gene editing potential of these two techniques to deliver multiplexed ribonucleotide proteins (RNPs) to generate triple-knock-out porcine embryos with a multi-transgenic background. We designed RNP complexes targeting the major porcine xenoantigens GGTA1, CMAH, and B4GALNT2. We then compared the development of mosaicism and gene editing efficiencies between electroporation and microinjection. Our results indicated a significant effect of voltage increase on molecule intake in electroporated embryos, without it notably affecting the blastocyst formation rate. Our gene editing analysis revealed differences among delivery approaches and gene loci. Notably, employing electroporation at 35 V yielded the highest frequency of biallelic disruptions. However, mosaicism was the predominant genetic variant in all RNP delivery methods, underscoring the need for further research to optimize multiplex genome editing in porcine zygotes.