GUANGZHOU, China –– Results of the first trial of gene editing in live human embryos were published in April of this year in the Beijing-based journal, Protein & Cell, restarting the debate on the ethics human gene alteration.
Click here for the published study.
The groundbreaking technique used by Junjiu Huang at the Sun Yat-sen University is called CRISPR/Cas 9 and was first developed by researchers at UC Berkeley in 2012. Since the discovery of the technique, it has taken over genetic labs with thousands of studies published since 2012. Each breakthrough using the CRISPR/Cas 9 technique has been increasingly controversial and has many scientists questioning the ethics of the gene manipulation.
Watch this video for a concise explanation of the CRISPR/Cas 9 technique.
CRISPR, short for “Clustered Regularly Interspaced Short Palindromic Repeats”, was first discovered by scientists in Japan studying the E. coli bacteria. A palindrome is a sequence of letters or numbers that is the same whether it’s read forwards or backwards. After publishing a paper on these patterns of palindromic DNA strips, many scientists have found similar structures in other bacteria.
The purpose of CRISPR was discovered around a decade later. Paired with Cas proteins and RNA segments, the CRISPR/Cas system is imperative for the bacteria’s immune system. When an invading source of DNA attacks the bacteria, the CRISPR/Cas 9 system allows the bacteria to incorporate the invasive DNA between the palindromic repeats of its own DNA. If the bacteria ever encounters the same invasive DNA, it can quickly identify and cut the foreign DNA, disabling it with the Cas protein’s specialized splicers.
Jennifer Doudna and Emmanuelle Charpentier, two researchers at UC Berkeley, successfully manipulated the CRISPR/Cas 9 system to cut a strand of DNA and replace it with a preferred DNA segment. This new gene-editing tool, much like a find and replace function, makes it easier than ever to change the genes of live cells, including those of humans.
Starting with individual cells such as human and mouse cells (2012), CRISPR/Cas 9 was soon applied to macaques monkeys and zebrafish in 2013. By the end of 2013, scientists could control the effects of the technique and get it to accurately create desired genes and in 2014, a liver disorder was successfully edited out of laboratory mice.
Although the jump in technology from animals to humans would be small, scientists are wary of crossing an ethical line. Many are concerned that humans may begin to “play God” or create “superhumans” with this new technology. The National Institute of Health, America’s largest sponsor in the field of biomedicine, released a statement stating the termination of all funding to gene alteration projects. In addition, two scientific journals (Nature and Science) refused to publish Huang’s study because of ethical reasons.
This hesitation comes with good reason. Not only is the technique still lacking, but it also changes how genes are passed down through generations. Since both chromosomes are altered, it creates a gene drive which completely defies Mendel’s hereditary laws. Gene drive shows how nearly 100% of all offspring will inherit the altered gene.
The high imprecision of this technique was highlighted by Huang’s study: out of the 86 human embryos used, 71 survived the treatment and only 54 were viable for genetic testing. Out of the 54 tested embryos, only 28 were successfully spliced and even less had successful integration of the desired gene. Many of the embryos with successful splicing were found to have strange mutations due to the CRISPR/Cas 9. Admittedly, the embryos used for testing were all embryos which were unable to come to full term which could have skewed the results.
Huang acknowledges that it was premature to start testing on embryos and is currently working with adult human cells to try and find a more precise technique. However, it is rumored that four other Chinese laboratories are doing similar research with human embryos.
Regardless of the ethics of CRISPR/Cas 9, this discovery is admittedly one of the greatest scientific breakthroughs of the decade. Hopefully after careful consideration and further research, there will be a cure for patients with hereditary diseases once and for all.
“The Age of the Red Pen; Genome Editing.” Economist 22 Aug. 2015: 18-21. Print.
Collins, Francis S., M.cd., P.h.D. “Statement on NIH Funding of Research Using Gene-editing Technologies in Human Embryos – The NIH Director – National Institutes of Health (NIH).” National Institutes of Health. National Institutes of Health, 29 Apr. 2015. Web. 07 Sept. 2015.
Cyranoski, David, and Sara Reardon2. “Chinese Scientists Genetically Modify Human Embryos.” Nature.com. Nature Publishing Group, 22 Apr. 2015. Web. 07 Sept. 2015.
Liang, Puping, Yanwen Xu, Xiya Zhang, Chenhui Ding, Rui Huang, Zhen Zhang, Jie Lv, Xiaowei Xie, Yuxi Chen, Yujing Li, Ying Sun, Yaofu Bai, Zhou Songyang, Wenbin Ma, Canquan Zhou, and Junjiu Huang. “CRISPR/Cas9-mediated Gene Editing in Human Tripronuclear Zygotes.” Protein & Cell 6.5 (2015): 363-72. Springer Link. Web. 04 Sept. 2015.
– Juyon Lee (‘18)