Shoukhrat Mitalipov and his colleagues from Oregon Health and Science University have successfully used the CRISPR Cas9 gene editing technology to wipe out a genetically inherited heart mutation in embryos. The study combined new technology (CRISPR-Cas9-based technology) with nature's own ability to fix DNA problems during certain cell cycles and involved researchers from Oregon Health & Science university, the Salk Institute, and the Institute for Basic Science in the Republic of Korea. This hereditary cardiac disease may cause sudden deaths, in particular during the practice of a sport. The experiments were privately funded; USA tax dollars aren't allowed for embryo research.
While none of the research so far has created babies from modified embryos, a move that would be illegal in many countries, the work represents a milestone in scientists' efforts to master the technique and brings the prospect of human clinical trials one step closer.
Furthermore, to be ethical, any applications or experiments utilizing CRISPR or other gene editing technology can not use any other methods in its process which are themselves intrinsically immoral, Fr.Pacholczyk said.
This is the first time gene editing on human embryos has been conducted in the United States. The embryos were created from eggs donated by healthy women, which were artificially inseminated with sperm from males carrying the mutation.
Salk's Jun Wu - one of the paper's authors - explained: "Our technology successfully repairs the disease-causing gene mutation by taking advantage of a DNA fix response unique to early embryos". If combined with other techniques, however, researchers say it could both cut out disease-causing genes and replace them with healthy versions to essentially cure genetic human diseases. The potential impact is huge; thousands of inherited diseases are caused by mutations in single genes, so editing the germline cells of individuals who carry these mutations could allow them to have children without the risk of passing on the conditions.
Gene editing in theory could rescue diseased embryos.
Using standard IVF techniques, the scientists first fertilised donor eggs with sperm containing the defective gene.
Molecular scissors known as CRISPR/Cas9 corrected a gene defect that can lead to heart failure. "The possibility of producing designer babies, which is unjustified in any case, is now even further away", Lovell-Badge said.
This image sequence shows embryos developing after injected CRISPR along with sperm from a man with a potentially fatal genetic mutation.
Mitalipov argues this means that the procedure should not actually be called gene editing, but that it is more of an assisted form of natural DNA fix. "The other barrier is, the (US Food and Drug Administration) is prohibited from considering any clinical trials related to germline genetic modification", she said.
The study results don't mean that editing human embryos to correct genetic diseases will be available at hospitals anytime soon.
The existence of the testing option means that gene editing of embryos has "a very narrow window of opportunities", says Lluís Montoliu, a genome researcher at the National Centre of Biotechnology in Madrid, Spain. Not only did a high percentage of embryonic cells get repaired, but also gene correction didn't induce any detectable off-target mutations and genome instability - major concerns for gene editing.
The highly controversial technique is still at an early experimental stage though and Dr Mitalipov made clear there is no question of any attempt being made to create babies with the genetic modification - something which would be illegal in the U.S. and the UK. They did this to modify the gene responsible for the blood disorder β-thalassaemia.
Now, when it comes to using CRISPR to correct gene mutations in embryos, Mitalipov said Tuesday, "We've done some ground work".
Scientists claim if these healthy embryos were implanted into a woman's womb, future generations would no longer inherit the illness. This time the researchers used normal embryos, which they found increased the proportion of embryos that were edited from 14% to 50%.
The level of efficiency is affected by the type of CRISPR machinery used and, critically, the timing in which it is put into the embryo.