A type of genetic engineering called genome editing is receiving worldwide attention as a technique that can produce amazing progress in medicine and improvement of agricultural products. But the technique, which precisely alters genetic sequences, has raised ethical and social questions. Given the move to strongly push research on genome editing in Japan, including human genome editing, it is imperative that the government and academic societies concerned work out strict rules because the technique at this stage is not fully reliable and its ethical, legal and social ramifications are not completely known.
In genome editing, targeted DNA in a cell is cut away at a specific location to inactivate a problematic gene or to insert a replacement DNA sequence for replacement or repairs in order to produce a desired result. While DNA is a substance that contains genes, a genome refers to the entirety of hereditary information contained in genes and chromosomes in cells. In humans, a copy of the entire genome — more than 3 billion DNA base pairs — is contained in all cells that have a nucleus. Since the accuracy of genome editing at present is not high enough and inaccurate editing can happen, there is a view that genome editing is not an established technique. The current mainstream method in genome editing is programming a complex made up of a guide RNA and a certain type of protein to target a problematic gene in DNA.
In April last year, news that Chinese scientists edited the DNA of human embryos — the first time this has been done — shocked the world and touched off a debate because of the ethical implication of such endeavors. A team of researchers at Sun Yat-sen University in Guangzhou injected 86 nonviable embryos with a complex called CRISPR/Cas 9 to modify the gene responsible for beta thalassemia, a fatal blood disorder. Of the embryos, 71 survived and 54 of them were genetically tested. It was found that just 28 were successfully spliced, but that only a fraction of them contained the replacement genetic material. The researchers also detected a number of "off-target" mutations apparently caused by the injection of the CRISPR/Cas 9 complex.