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By Ashley Nee, '22 Recently, a group of Chinese researchers led by Jiankui He claimed that they had created the world’s first genetically modified human twins. The twins were born this November from embryos that were designed with CRISPR-CAS9 technology to theoretically be more resistant to HIV infection. The veracity and success of the researchers’ claims have been called into question; even still, the act of genetic modification on humans both violates a 2003 health-ministry guideline and ethical protests made by many both within and outside of the scientific community. [1]  The twins were genetically modified through the use of the gene editing technique CRISPR-CAS9 technology. CRISPR refers to a group of related DNA sequences that are naturally used by organisms like bacteria and archaea as protection against viruses. [2] CRISPR sequences contain repetitive base sequences followed by segments of foreign DNA from, for example, a virus that had previously integrated into the genome. [2] CAS9 enzymes then use CRISPR sequences as guides to search for foreign DNA sequences in order to then cleave them. [2] The function of CRISPR and CAS9 is applicable to gene editing, as the sequences in CRISPR that would otherwise hold sequences complementary to those of viruses can be replaced with other genes.
In the case of the genetically modified twins, the CCR5 gene was disabled through the use of CRISPR-CAS9. CCR5 is commonly used as a co-receptor by HIV to enter cells, so the disablement of CCR5 may theoretically stop HIV from infecting its target cells. [1] Though this edit is potentially beneficial , it remains unknown whether or not CRISPR-CAS9 is safe for use in humans, as gene editing may inadvertently damage other genes or result in other unforeseen consequences. Thus, when He gave a presentation regarding his work on November 28, many in the scientific community decried his work as potentially unsafe, medically unnecessary, and as a violation of ethics and law. Further, the Chinese government has also ordered an investigation to verify He’s statements and determine whether or not genetic editing occurred as well as a suspension on He’s research activities. [1] Such a strong response by both politicians and scientists provides a great testament to the improvement in accountability in science, but it also, according to some, calls for a global contract regarding gene editing in humans. [1] References: 1. Saey T. The Researcher who created CRISPR twins defends his work but fails to quell controversy. ScienceNews [Internet]. 28 November 2018 [Cited 28 November 2018]. Available from: https://www.sciencenews.org/article/researcher-defends-creating-crispr-babies-fails-quell-controversy?tgt=nr 2. Reis A, Hornblower B, Tzertzinis G. CRISPR/Cas9 & Targeted Genome Editing: New Era in Molecular Biology [Internet] [Cited 28 November 2018]. Available from: https://www.neb.com/tools-and-resources/feature-articles/crispr-cas9-and-targeted-genome-editing-a-new-era-in-molecular-biology
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