Twenty Thousand Mutant Mice

A May 2014 editorial in the journal Nature described “a project that aims to mutate every gene in the mouse genome to improve our knowledge of mouse biology,” that “should help avoid irreproducible results and costly failures in drug development.” At a cost of nearly $1 billion, the International Mouse Phenotyping Consortium wants to find out what changes occur to the mouse, when each of nearly 20,000 genes are removed.

This is the very definition of a fishing expedition. Therapies that successfully treat mutant mice routinely fail on human subjects in the clinic. Results from one lab are often irreproducible due to differences in environment, mouse strain, food, handling, etc. Most importantly, mutant mice often suffer significant health problems. Alteration of a single gene rarely has a single outcome. Instead, there are unintended effects that can cause pain and distress to the mouse. For example, attempts to create mutant mice to study human cleft palate conditions resulted in mice with severe facial or limb defects, delayed lung formation, and poor heart function, or in mice that died shortly after birth. Producing mutant mice, simply to see what happens, flies in the very face of the principles of the 3Rs (Reduction, Refinement, and Replacement) for animals in research. The motives and potential outcomes of this endeavor must be examined carefully before millions of mice suffer needlessly.