Ethics of Research involving animals
GM disease models (Chapter 7)
10.16 GM animals are increasingly being used in the study of human disease. Scientific advances allow the creation of animal models of diseases with a genetic component in a targeted way, reflecting the genetic patterns that underlie the human version of the disease. Examples include models for diabetes, deafness, psychiatric disorders, neurodegenerative disorders and cancers.
10.17 Some animals are used for the study of genetic diseases because of the strong genetic similarities between humans and many other species. For example, 99 percent of genes in mice have direct counterparts in humans (paragraph 7.2). Most biomedical scientists
maintain that the similarities between mice and humans are sufficient to make informative comparisons. Furthermore, the differences may be as instructive as the similarities when investigating the mechanistic basis of disease (paragraph 7.10). Scientists using animals in this field therefore maintain that careful analysis of mouse models can provide significant information on the function of genes in mammalian disease processes (paragraph 7.10). Other species with suitable genomes for comparative studies such as the zebrafish and the rat are being increasingly used (paragraphs 7.11-7.13).
10.18 Information from mouse models has enabled scientists to investigate the relationship between mutations and the nature and severity of the disease they cause. The glucokinase gene in diabetes is one such example. The use of the mouse model shaker1 has also led to the discovery of a gene causing profound hearing loss in both mice and humans (see paragraph 7.9). Mouse models are also important for investigating how one disease can produce varying symptoms in different individuals. Indirect changes, for example in levels of a protein or a hormone, may prove to be more suitable therapeutic targets than the genes themselves, as in the case of patients with neurodegenerative disorders (see paragraph 7.9). The use of GM animals can entail a wide range of welfare implications, as the animals involved usually suffer from the disease being studied for the duration of their lives (paragraph 4.57). They are also likely to be the subject of procedures carried out to characterise the different stages of the disease, including blood, metabolic and behavioural tests. The very low success rates in producing a strain of animal that can serve as a disease model also require attention (see Box 5.6).