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    Genome editing of human embryos in UK reveals key gene function in human embryogenesis

    Researchers have used genome editing technology to reveal the role of a key gene in human embryos in the first few days of development. This is the first time that genome editing has been used to study gene function in human embryos, which could help scientists to better understand the biology of human embryo development.

    In contrast to previous research that attempted to fix disease-causing mutations in human embryos, in the hope of eventually preventing genetic disorders. Whereas those studies raised concerns over potential ‘designer babies’, the latest paper, published on Sep. 20 in Nature, used CRISPR-Cas9 technique to disrupt the production of a protein called OCT4 that is important for embryo development.

    The team, led by developmental biologist Kathy Niakan of the Francis Crick Institute in London, used a total of 58 embryos that had been generated in fertility clinics as a result of in vitro fertilization (IVF) treatments. The embryos were no longer needed for IVF and had been donated for research. The UK Human Fertilisation and Embryology Authority granted permission to do the study — the first time a national regulator has approved research involving gene editing in human embryos (previous studies in other countries were endorsed by local review boards).

    CRISPR–Cas9 gene editing cocktail was injected into the embryos when the fertilized eggs, or zygotes, consisted of just one cell and their development were followed in the lab for a week. It soon became clear that normal development had derailed in embryos that lacked normal levels of OCT4. About half of the controls (which had unaltered, normal OCT4 levels) developed to form multicellular embryos called blastocysts. Of the edited embryos with disrupted OCT4 levels, only 19% made it that far.

    Researchers have traditionally done such studies in mouse embryos, which are more plentiful and carry fewer ethical considerations than human embryos. But the latest study highlights key differences between the role of OCT4 in human and in mouse embryos, underscoring the limitations of relying on animal models.

    The results will reassure scientists that CRISPR–Cas9 is efficient enough for studies in human embryos, says Fredrik Lanner, a developmental biologist at the Karolinska Institute in Stockholm. “If you do this in mice, you can test hundreds of embryos,” he says. “But you have a limited access to human embryos.”

    Read more: “Genome editing reveals a role for OCT4 in human embryogenesis”, Nature 2017, doi:10.1038/nature24033