Mus Musculus (House Mouse)
The mouse is one of the most useful models for comparison to humans as it is also a mammal. The mouse genome was sequenced in 2002 and it was shown that almost every gene in the mouse genome had a human homolog. The first mouse gene was isolated in 1977 and started a huge growth in mouse genetics.
Advantages of the mouse as a model organism:
- Small vertebrate
- Mammal therefore a model for man
- Have Embryonic Stem Cells
- Fairly quick reproduction rates – therefore several generations in a short amount of time.
- On implantation contains embryonic and extraembryonic tissue like humans
- Better tools for probing the immune, endocrine, nervous, cardiovascular, skeletal and other complex physiological systems that they share with humans.
Disadvantages of the mouse as a model organism:
- Poor accessibility as embryo develops inside womb.
- Small batches of embryos ~10 per litter.
- Expensive to keep in a lab.
What can the mouse be used for:
- Targeted Transgenesis.
- Mutagenesis.
Mice can be used to produce knockout models for human disease, this was first developed in the late 1980s:
Cystic Fibrosis (CFTR gene)
Atherosclerosis (apolipoprotein B)
Susceptibility to cancer (tumour suppressor genes)
If you mutate a gene in the mouse embryonic stem cells then this mutation can be passed down through the germline. The embryonic stem cells can become part of a new embryo and grow into an adult mouse.
Mice in medical research:
Mice are especially good models for human conditions such as obesity, cancer and immune system defects as these also occur in the mouse naturally the same as humans. Other diseases that do not usually affect mice such as cystic fibrosis and Alzheimer’s can be induced in the mouse by manipulating the genome.
Models developed:
Down's Syndrome - It occurs once in every 800 to 1,000 live births making it the most common human birth defect. It results from an extra copy of chromosome 21, known as trisomy. The Ts65Dn mouse, developed at The Jackson Laboratory, mimics trisomy 21 and exhibits many of the behavioural, learning, and physiological defects associated with the syndrome in humans, including mental deficits, small size, obesity, hydrocephalus and thymic defects.
Reference: https://www.nhgri.nih.gov/10005834
Cancer - The p53 knockout mouse has a Trp53 tumour suppressor gene that can’t elicit any effect. This makes the mouse more susceptible to tumours including lymphomas and osteosarcomas. The mouse has proved an important model for human Li-Fraumeni syndrome, a form of familial breast cancer.
Reference: https://www.nhgri.nih.gov/10005834
References:
https://www.nhgri.nih.gov/10005834
https://genome.wellcome.ac.uk/doc_WTD023552.html
Image courtesy of Wikimedia Commons.