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A Mice Life

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Lab mice are far more experimental than commonly thought.

The phrase ‘mouse model’ may inspire thoughts of eager rodents twitching their whiskers in the hope of making it big. But in the world of biomedical lab work, choosing the right mouse model for your experiment is an integral step in the scientific process.

When listening to a podcast on Alzheimer’s disease, I stumbled upon a question of diseased mice – are they given the diseases or are the symptoms found? Upon investigating, it seems the world of murine breeding is far more intriguing than you would imagine.


Lab mouse being posed for a photograph. Global Panorama, Flickr.

Though it has long been agreed upon that rodents are the best human substitutes in trials due to their genomic simplicity and similarity to humans, and the relatively low sale price, the simplest decision when purchasing subjects is the choice between mice and rats. Rats are considered to be more intelligent. Unfortunately, they are large causing the cost of their housing and wellbeing to be higher; this is well worth the expense to any of those needing to disassemble and study internal matters. Mice are far more popular in the field of genes and diseases as there are more advanced tools to work with.

It is these tools that answer my original question – mice are not found to have diseases similar to humans, they are designed into their DNA. The most common way of procuring rodents for scientific purposes is to buy them off of labs that specialise in creating mouse ‘models’. These models can be immunodeficient, inbred, outbred, have cardiovascular diseases and so on and so forth including mixes of many different degenerative edits. 
The Jackson Laboratories in America are currently one of the largest suppliers worldwide as they breed millions of mice in thousands of different models a year. Their website not only links to mouse genome database but their own magazine and podcast relating to their studies. As they approach a monopoly on the mice breeding industry, previous methods of acquiring mice begin to be revisited.
Lab mouse.

Lab mouse. Mycroyance, Flickr.

The switch from pet store mice to lab-bred mice was largely due to the increasingly controlled care conditions of the labs. Following research on mice stress, laboratories keep their mice at a temperature of 18-23ºC, at a humidity between 40 and 60%, eating a fat content of 4-11% and prevent direct handling by males. The control over their living conditions prevents much of the ‘nurture’ differences in personality and biology which may otherwise compromise results.
Due to the strict conditions purchasing from breeders can be expensive – one immunologist shared online that the cost of an immunodeficient NSG model is over four times the $30 price tag of a common C57BL/6 mouse at 12 weeks old. However, the commercialisation of CRISPR technology now allows labs to create their own subjects that fit the purposes of their experiments, without having to pay tens of thousands to breeders for unique genomic sequences.
The use of mice in experiments has forged medical science as we know it today, though the methods used would not have been recognised by the scientists who drafted them.