Is It Too Soon?

(May 5th, 2015) A recent study on human germline gene editing has thrown the scientific world into turmoil. Many wonder: ”Are we ready to cross that line?” We asked Christine Mummery, member of the International Human Embryonic Research Guidelines Task Force, for her opinion.

Last month, a group of Chinese researchers revealed the results of their attempt to manipulate the human germline genome. In a controversial paper entitled "CRISPR/Cas9-mediated Gene Editing in Human Tripronuclear Zygotes", the researchers describe the use of this gene editing technology applied to human embryos for the first time. As proof-of-concept, they successfully cleaved the endogenous beta-globin gene in tripronuclear (3PN) zygotes using CRISPR/Cas9.

Aware of the limitations, the team also raised concerns about its efficiency and specificity. "Our study underscores the challenges facing clinical applications of CRISPR/Cas9," they conclude. "Further investigation [...] is surely needed. In particular off-target effect of CRISPR/ Cas9 should be investigated thoroughly before any clinical application."

However, calling for more drastic measures, the International Society for Stem Cell Research (ISSCR) reiterates its appeal for a moratorium on this type of research only a month after their initial statement regarding human germline genome modification.

For the ISSCR, before any practical applications, it's imperative to conduct an extensive risk analysis alongside public discussion about potential ethical implications. "The moratorium was issued because it was felt that the ethical debate needed to take place first on whether the moral line should be crossed and future generations impacted," explains Christine Mummery, based at the University Medical Centre in Utrecht, the Netherlands and member of ISSCR's International Human Embryonic Research Guidelines Task Force. "At present it is not safe [...] and society will have incorrect perceptions of the outcome, for good and bad."

Gene editing procedures have come a long way over the last few years. In fact, this procedure has now been applied to animal cells, including early embryos and gametes. Despite these successes, and although not outright against the procedure, the ISSCR felt this jump from other animals to humans was a step too far, given our current lack of understanding of potential long term risks, including the fear that it will affect unrelated genes. For Mummery, public debate is essential to "dispel the Frankenstein ideas or that you can create designer babies, super intelligent, highly sportive." The public need to get the correct information in a simple and straightforward way.

Whichever the side of the argument they defend, all researchers agree that CRISPR/Cas9 is becoming an increasingly popular technique, which can be used in a wide range of applications, from gene editing and gene therapy to investigating gene functions. However, for the ISSCR it is simply too soon to apply it to the human germline, even in a research setting, let alone in a clinical setting. According to Mummery, the best approach is to improve the technique first, followed by public debate as to if, how and when to use this approach. "I think the research on the technique will continue and it will improve to the extent that risks are minimal," defends the researcher. "We should then revisit the question of whether it is desirable. I have no principle objections to using it for the most serious of conditions but there has to be consensus on what those are."

The ISSCR's "Guidelines for the Conduct of Human Embryonic Stem Cell Research," defending ethical, responsible and transparent research practices involving human embryos, can be found at

Alex Reis

Photo: Rondeau (scissors), National Human Genome Research Institute (DNA)

Last Changes: 06.19.2015