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Anonymous
Correction of a pathogenic gene mutation in human embryos 2017-08-03 03:16:57 Post No. 9081627
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Correction of a pathogenic gene mutation in human embryos 2017-08-03 03:16:57 Post No. 9081627
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Correction of a pathogenic gene mutation in human embryos
Anonymous
2017-08-03 03:16:57
Post No. 9081627
[Report]
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature23305.html
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.
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Key Highlights:
These WGS results support our Digenome-seq conclusions that gene correction did not induce any detectable off-target mutations in selected blastomeres
Taken together, these Digenome-seq, WGS and WES results demonstrate high on-targeting specificity of CRISPR–Cas9 in human embryos without any off-target effects.
This striking difference implies that human gametes and embryos employ a different DNA damage response system, perhaps reflecting the evolutionary importance of maintaining germline genome integrity
On the basis of our results, it may not even be necessary to provide exogenous oligo templates for gene correction in heterozygous human embryos.
Despite remarkable targeting efficiency and high HDR frequency, some CRISPR–Cas9-treated human embryos demonstrated NHEJ-induced indels and thus would not be suitable for transfer. Therefore, genome editing approaches must be further optimized before clinical application of germline correction can be considered.
CRISPR–Cas9 targeting seen in our investigation was very accurate, providing assurance regarding safety concerns.
As indicated, PGD may be a viable option for heterozygous couples at risk of producing affected offspring. In cases when only one parent carries a heterozygous mutation, 50% of embryos should be mutant. In contrast, targeted gene correction can potentially rescue a substantial portion of mutant human embryos, thus increasing the number of embryos available for transfer.
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