Genetic Engineering Publications - GEG Tech top picks

Whether CRISPR system was applicable in normal human (dual pronuclear, 2PN) zygotes was unclear. Here the scientists demonstrate that CRISPR/Cas9 is also effective as a gene-editing tool in human 2PN zygotes. By injection of Cas9 protein complexed with the appropriate sgRNAs and homology donors into one-cell human embryos, they demonstrated efficient homologous recombination-mediated correction of point mutations in HBB and G6PD. However, their results also reveal limitations of this correction procedure and highlight the need for further research.

Researchers in China have reported editing the genes of human embryos to try to make them resistant to HIV infection. Their paper which used CRISPR-editing tools in non-viable embryos that were destroyed after three days is only the second published claim of gene editing in human embryos.

Genome editing has potential for the targeted correction of germline mutations. Here we describe the correction of the heterozygous MYBPC3 mutation in human preimplantation embryos with precise CRISPR–Cas9-based targeting accuracy and high homology-directed repair efficiency by activating an endogenous, germline-specific DNA repair response. Induced double-strand breaks (DSBs) at the mutant paternal allele were predominantly repaired using the homologous wild-type maternal gene instead of a synthetic DNA template. By modulating the cell cycle stage at which the DSB was induced, we were able to avoid mosaicism in cleaving embryos and achieve a high yield of homozygous embryos carrying the wild-type MYBPC3 gene without evidence of off-target mutations. The efficiency, accuracy and safety of the approach presented suggest that it has potential to be used for the correction of heritable mutations in human embryos by complementing preimplantation genetic diagnosis. However, much remains to be considered before clinical applications, including the reproducibility of the technique with other heterozygous mutations.

In this work, the scientists have co-injected Cas9 mRNA, gRNAs, and donor DNA, they successfully introduced the naturally occurring CCR5Δ32 allele into early human 3PN embryos. In the embryos containing the engineeredCCR5Δ32 allele, however, the other alleles at the same locus could not be fully controlled because they either remained wild type or contained indel mutations. This work has implications for the development of therapeutic treatments of genetic disorders, and it demonstrates that significant technical issues remain to be addressed. The authors advocate preventing any application of genome editing on the human germline until after a rigorous and thorough evaluation and discussion are undertaken by the global research and ethics communities.