Comment

Over the past few years it has become increasingly clear that new insights into the physiology of the gut are being made by non-gastroenterologists, often working on “blue-sky” projects with no clinical relevance. One such project, published in Cellearlier this year, illustrates this point well.

Astrocytes are cells with branching cytoplasmic processes which surround nerves. Some of the processes are directed towards capillaries and others towards neurones. They provide structural support for the neurone, play a role in maintaining the blood–brain barrier, and are also important in repair after injury. They contain a characteristic protein–glial fibrillary acidic protein (GFAP). Bush and colleagues used the GFAP promoter to target the thymidine kinase of herpes simplex virus (HSV-TK) into astrocytes in transgenic mice. In proliferating cells exposed to the antiviral agent ganciclovir (GCV), HSV-TK metabolises GCV to produce toxic nucleotides which kill the cells expressing the transgene. Untreated transgenic mice are normal. However, when GCV was given to the transgenic mice in subcutaneous miniosmotic pumps, starting at about two weeks after implantation, the mice began to die. By 20 days treatment mortality was 100%.

When the mice were analysed, the cause of death was clear—they all had a fulminant …