Gene Therapy

One form of genetic engineering on trial at the moment in humans is gene therapy. Gene therapy is being used to treat diseases that are caused by a single defective gene, of which there are approximately 2,800 known diseases. These include haemophilia, muscular dystrophy, cystic fibrosis and Tay-Sachs disease.

The mutations that cause these diseases can occur randomly and can also be passed on from generation to generation. The most famous example of this is the haemophilia gene carried by Queen Victoria, which was passed on to many of her descendants in the 19th and early 20th centuries.

The idea behind gene therapy is to put a correct copy of the gene that is missing into the cells, so that patients can make the protein they need.

The idea for gene therapy was proposed 15 years ago and scientists were very optimistic about the possibilities this treatment could offer. Since the first trial conducted in 1990, there have been around 400 gene therapy studies worldwide.

Unfortunately, getting gene therapy to work in reality has proven to be a difficult challenge and there have been many setbacks. One of the main problems has been getting the gene into the cells. Researchers have found viruses to be the most effective vessels as they naturally go into our cells and put their DNA into ours. But the death of a young boy called Jesse Gelsinger, who was undergoing a gene therapy trial, was perhaps the worst moment in gene therapy history. He died because of a immune response to the virus that was used. Many people were angry and felt that scientists were pushing the research ahead too fast and questions were raised about whether gene therapy would ever work.

A few years later, there is new hope, with several trials reporting very promising results, including a haemophilia trial being conducted in the US. But again tragedy struck when two of the boys on another trial in France were reported to have developed leukaemia following gene therapy treatment.

The problem seems to be with the viruses being used. These are used because they naturally entwine their DNA with ours, but a drawback of this is that most of the time the new gene gets inserted randomly into the cells’ DNA. This is usually fine, because most of the DNA in our cells is redundant. But the danger is when the new gene inserts itself into a part of the DNA that does have a function and, by doing this, disrupts the function of the normal gene. This is what happened with the boys on the French trial. The new gene inserted itself into a gene involved in cell division, so the cells began dividing uncontrollably resulting in leukaemia.

There are still many obstacles to overcome before gene therapy becomes a standard form of treatment, but, if it does work, it could rid us, not only of single gene defects, but perhaps more complicated diseases, where more than one gene is involved, such as diabetes or heart disease.

Once we are able to cure diseases using gene therapy it may also be applied cosmetically, for example - having a gene inserted to make you more muscular or to stop you going bald.

Gene Testing
Although some gene mutations lead to diseases from birth, other gene mutations only make people more susceptible to certain diseases, such as Huntingdon’s disease and breast cancer. You can now have a genetic test see if you have these mutations. This does not necessarily mean you will get the disease, but means you have a higher than average chance of developing it, for example - women with the BRCA1 gene have an 80% chance of developing breast cancer by the age of 65.

There are concerns that, if gene testing become widespread, people may be discriminated against because of their genes by insurance companies and employers.