The history of the mouse, Mus musculus, as the stereotypical lab animal dates back to the early 1900s. Researchers discovered that the mouse’s small size made it an excellent research animal. Also, mice are famous for their prolific breeding. They reach sexual maturity at the age of about 4 weeks, are sexually receptive every few days, and give birth to litters of 1 to 10 pups after a gestation of only about 3 weeks. Over a life span of 1.5 to 3 years, a single pair of mice can produce hundreds of offspring.
Researchers have benefited from biotechnology in their studies of mice. Transgenic mice have been available since the 1980s. These mice are modified in countless ways, including altered susceptibility to human diseases. Another biotechnology, cloning, was applied to mice in 1998, making possible the production of genetically identical animals ideal for testing new disease treatments. The mouse genome sequence was completed in 2002, revealing about 30,000 genes divided among 20 chromosomes. Not surprisingly, most mouse genes have counterparts in the human genome. This genetic similarity has made possible some of the following ways in which Mus musculus has contributed to biological research:
In the 1930s, the discovery that mice reject transplants from all but their very close relatives led to the discovery of the major histocompatibility complex (MHC). Since that time, biologists have discovered an array of genes related to immune function.
Mice have been used to study human disease since the 1930s, when researchers discovered that mice could contract yellow fever. Vaccines were subsequently tested in mice. The availability of transgenic mice has opened new possibilities for research on the cause and treatment of human disease, including muscular dystrophy, Alzheimer disease, obesity, Parkinson disease, cancer, and HIV/AIDS.
X chromosome inactivation
In the 1960s, biologist Mary Lyon proposed that in female mammals, one of the two X chromosomes is inactivated early in embryonic development. This phenomenon, which is now often illustrated using calico cats, was first proved in mice with mottled coats.
These undifferentiated cells, which can be derived from embryos or adults, can specialize into many other cell types. Mouse stem cell research has shown great promise in treating spinal cord injuries and many other ailments.