Lack of applicability to humans – some examples: 1. Only recently, researchers from the US and Canada studying heart disease found that, although their gene-mutated mice5 showed an improvement in heart function, human patients with a mutation in the equivalent gene show such severely reduced heart function that two patients with the mutation required a heart transplant before they reached the age of 30yrs6 .
2. A gene called “Large tumour suppressor 2” was known to prevent tumour development in people, yet it didn’t have that effect in mice. The mice with this gene knocked-out (so that tumour suppression would be switched off) still did not develop cancer.
3. The “klotho” gene in humans is known to be involved in coronary artery disease and heart disease. But this wasn’t the case in the knockout mice. Mice with the klotho gene knocked out were very small and sickly and died prematurely at 9 or 10 weeks of age, but they did not suffer any heart problems.
4. In cystic fibrosis (CF) research, mouse ‘models’ have delayed research and could have held up the search for a treatment for the disease. Mice with mutations in the equivalent gene that is at fault in CF patients are being used to study the condition, but often do not suffer from any lung disease, which is fatal in 95% of human patients.