4 Germline gene therapy
Now that in vitro fertilization – bringing eggs and sperm together outside the prospective mother's body – is an established technology, the possibility exists that genes could be altered in eggs or sperm, or in a very early embryo. The obvious advantages of germline gene therapy are that the cells are accessible (because they are outside the body), so gene delivery is less of a problem than it tends to be with somatic cells; and the inserted gene (or genes) would be present in all the cells of the person so treated because it would be transmitted to progeny cells during growth and development.
Would a person who had received germline gene therapy transmit the inserted gene(s) on to their children?
They would also pass it on, because it would be present in their germline cells as well as their somatic cells.
This might be poor business for gene therapy companies, but could be good for people with a genetic disorder.
Until recently, there was widespread agreement that germline gene therapy in humans should be ruled out. It is currently (early 2005) banned in the UK. It is not possible to predict where in the genome a newly inserted gene might end up, and this poses unknown risks of causing new mutations, or otherwise disrupting normal gene functioning. Even if these hazards could be removed, there are new ethical problems that could appear with serious development of germline therapy. These include how to decide which genetic alterations to permit. Some would clearly be aimed at correcting harmful mutations, but others might be considered enhancements, rather than treatments. Sometimes, it may be hard to tell the difference.