Humans who have had their genetic material modified could exist in the next two years. A US based company announced plans to start trials to genetically edit patient’s DNA who suffer from the genetic condition ‘leber congenital amaurosis’.
The private biotech company, Editas Medicine, are set to manipulate human genes to reverse blindness,says chief executive of Editas Medicine Katrine Bosley. The rare inherited condition affects retinal function: the specialised tissue at the back of the eye that detects light and colour. Sufferers are affected from birth, or during the first few months of infancy, and can eventually become completely blind. Hereditary eye diseases are already precedent in gene therapy, for example in the treatment of choroideraemia, a disease causing progressive blindness therefore it seems an obvious starting point for genetic modification. However, GM is banned in the United States and the company requires special permission from health professionals to carry out trials.
The condition is the result of a defect in the RPE65 gene that codes for a proteins essential in competent vision. Scientists working for the private company have confidence in the ground-breaking technique used to fix this defected gene, thus preventing disease.
The science behind the procedure is complex. It involves a naturally occurring defence mechanism used by bacteria called CRISPR, or ‘Clustered, Regularly Interspaced, Short Palindromic Repeat’. This is a section of prokaryotic DNA containing short repetitions of base sequences.
The CRISPR system protects bacteria against viruses. When the bacteria detects the presence of viral DNA within the cell, it produces two types of short RNA. One of these RNA strands matches the sequence of the invading virus. A complex is formed, built from the two RNA strands and nuclease type enzyme that cuts DNA. When the matching sequence finds its target within the viral genome, the enzyme cuts the DNA disabling the virus. Researchers have found this mechanism could be engineered to cut any DNA sequence by changing the RNA sequence to match the target. When the DNA is cut, the cell tries to repair DNA which is error prone. The gene becomes disabled due to mutation, allowing researchers to understand the genes function.
Replacing the mutant gene with a healthy copy allows increased precision for research. This addition can be achieved by adding another section of DNA carrying the desired sequence. It will pair with the cut ends, recombining and replacing the original sequence with the new version. According to the MIT Technology Review, patients will have a range of viruses fed into their eye that include instructions to delete a mutated gene in photoreceptor cells.
The morality of this genetic modification is questionable, causing conflict between science and ethics. As the patient’s genome is altered, it could be passed down to their offspring. Also there is possibility of unintended detrimental effects to the patient’s genome. Ultimately where will it stop, could this lead to controversial “designer babies”?
It appears CRISPR technology is still a matter of science fiction and increased research is required to eradicate possibilities of unwanted mutations and to ensure efficiency and safety. It is suggested that the ultimate motives of the company are extremely premature. Although researchers recognize that CRISPR has huge potential for preventing genetic disease and helping families desperate for cures.
Gene editing is much more feasible today than it has ever been and these trials could provide a promising future in the fields of genetic disease and medicine.