Genetics... new and amazing discoveries are being made every day! Transgenic animals are an excellent tool for medical research: they allow for a better understanding of emerging therapies as well as a means to efficiently manufacture pharmaceutical products. Transgenic animals are produced when a gene from one animal is integrated into the genome of a different species. There are several ways that transgenic animals can be made; this article focuses on the most common and versatile method, pronuclear microinjection. Using this method, fertilised eggs are isolated from a donor animal and injected, using a fine glass needle, with foreign DNA. The engineered eggs are then implanted into a surrogate mother. The desired characteristics are expressed by cells that successfully incorporate the transgene (genetic material that has been transferred from one animal to another). The flow diagram below briefly illustrates the production of transgenic mice using the pronuclear microinjection method.
Figure 1: Foreign DNA is injected into mouse eggs to produce transgenic mice.
The idea of transgenic animals was established in the 1980’s but it was not until 2006 that the first therapeutic product was approved (2009) . The term “pharming” refers to the manufacturing of pharmaceutical products, especially protein products, in transgenic animals (Niemann and Kues, 2007).
Transgenic mice have recently been used to model the progression of neurodegenerative diseases such as Alzheimer’s disease. Previously it was difficult to find a good transgenic model for Alzheimers, as the mice only demonstrated certain characteristics. The latest transgenic mouse however, express more characteristics of the disease making them a more reliable model. Studies found that transgenic mice that over express mutant forms of human amyloid precursor protein (APP) are more likely to suffer an early onset of Alzheimer’s disease. From this discovery it can be inferred that humans who have higher levels of mutant APP will also suffer an early onset of Alzheimer’s Disease. The next step was to use transgenic mice to investigate suitable therapies for Alzheimer’s disease. (D. Skaper, 2010)
2009. Animal Pharming: Past Experience and Future Prospects. Berlin, Heidelberg: Springer Berlin Heidelberg.
D. SKAPER, S. 2010. Editorial [Hot topic: Transgenic Animal Models of Neurodegenerative Diseases (Guest Editor: Stephen D. Skaper)]. CNS & Neurological Disorders - Drug Targets (Formerly Current Drug Targets, 9, 384-385.
NIEMANN, H. & KUES, W. A. 2007. Transgenic farm animals: an update. Reproduction, Fertility and Development, 19, 762-770.