If we learn how to change genes of embryos in a safe way we can prevent hereditary diseases
To free families from the curse of hereditary diseases, medical geneticists dream of changing human DNA before birth. But the dream is also a nightmare because it raises the possibility of babies on order or the creation of harmful mutations. Now, the precision of a new genome editing method, called CRISPR-Cas9, brings both the dream and the nightmare to the brink of reality.
The method makes it possible to cut and remove problematic DNA segments from the genome easily and at a low cost compared to other methods. Scientists are testing whether it can be used to treat genetic diseases, such as cystic fibrosis, or other conditions, such as HIV, in adult human cells. But no one has tried to edit cells that can pass the DNA from generation to generation: egg cells, sperm or cells of early stage embryos. Such cells belong to what is called the germ cell line. In April 2015, a group at Sun Yat-sen University in China reported that its scientists had crossed that line.
Rumors of such research have already caused panic. In March, the authors of a well-received editorial in Nature called for halting changes in all human germ cells, both for research and clinical use, as the Center for Genetics and Society in Berkeley, California, did. But a total ban is a misstep.
The Chinese group used CRISPR on early-stage embryos that carried genetic material from two sperm cells instead of one. Such embryos do not develop properly, so fertility clinics get rid of them. The researchers tried to correct a mutation in the gene that causes beta-thalassemia, a blood disease that can be fatal. The results of the study, published in the scientific journal Protein & Cell, show that CRISPR failed to correct the mutation in most embryos and caused unexpected changes elsewhere in the genome. (Scientific American, Nature and Protein & Cell belong to Springer Nature.) The study showed that the method, as it is used today, has too many missing factors and there is no justification for endangering human life in its use.
There is no doubt that changes in the genome of germ cells intended for fertilization must be stopped. Scientists still need to learn how CRISPR works. Moreover, they still do not know enough about how genes react with each other and with the environment in disease processes. Funding foundations are prohibited from supporting research with embryos suitable for reinsertion and journals from publishing such research.
But scientists should be allowed to do basic research on changing human stem cells, the International Society for Stem Cell Research and other groups have argued. Such studies can be conducted on embryos in early stages, which cannot develop into a live baby. Such genetic engineering may stop fatal diseases such as Huntington's disease or muscular dystrophy before they break out in the offspring, and prevent the inheritance of the damaged DNA to additional offspring. The risk is that unexpected and harmful changes will also be inherited. Researchers need to conduct extensive studies before clinical use can be considered. Today, IVF parents can scan embryos at early stages to detect certain genetic diseases. However, there are couples who are unable to produce healthy embryos or who do not wish to produce more embryos than they need for ethical reasons. Germ cell DNA editing could help them.
In the US, we would like basic research on germ cells to be conducted with the help of federal funding, because it would allow more resources and more transparency, but such research would have to win private or state funding. After the study was published in Protein & Cell, the US National Institutes of Health (NIH) came back and said they would not fund research involving the modification of human embryos, due to legal reasons and safety concerns.
These issues indicate that scientists and government officials should engage the public in discussions about changes in germ cells and use these discussions to design new policies. CRISPR is the most powerful tool available today for DNA editing. We must explore its potential to prevent the harms of genetic diseases, but do so without jeopardizing our values or future generations of human life.
On the issue in the Israeli context, see "Reflections - a baby with blue eyes? / Bracha Reger, from the same issue of Scientific American
The article was published with the permission of Scientific American Israel
