Mouse (Mus musculus) 

About the mouse:

Gremlin expression (blue) in heterozygous (left) and homozygous (right) mutant embryos.

The common house mouse Mus musculus has had an association with humans since we first began farming and storing grains, which mice were more than happy to share. Starting in the 18th century and continuing today, mice have been collected and bred for their unique coat patterns. Today, the mouse is the premier model organism for mammalian genetics and the study of human biology.

Mice were first studied genetically in the early part of the 20th century, with Lucien Cuénot demonstrating mendelian inheritance of coat color in 1902. Clarence Little, along with William Castle, pioneered the use of the mouse as a genetic model organism, developing many of the inbred mouse strains which are commonly used in laboratory research, including the "Black 6" strain C57BL/6, the target of the mouse genome sequencing effort. In 1929, Little founded the Jackson Laboratory, which today continues to develop and maintain strains of mice for biological research.

Mice have a number of desirable traits making them ideal for study. They are small and easy to keep in the laboratory, and have a short generation time, which makes them suitable for genetic analysis. Mice are by far the best developed mammalian system for genetic analysis. Use of mice enables the study of many uniquely mammalian properties, including the immune and endocrine systems, as well as embryonic development.

The development of transgenic technologies in the 1980's allowed researchers to manipulate the mouse genome in very precise ways.  Genes can be "knocked out", eliminating their function, while mutant genes can be "knocked in" to study the effects of various mutations. Using these and other tools, researchers have been able to develop strains of mice which serve as models of many human diseases, including cancer, cystic fibrosis, and diabetes, facilitating the study of these diseases and the design of potential therapies.The mouse genome was sequenced in 2002. At about 2.5 billion base pairs and 22,000 genes, it is roughly comparable to the human genome. In fact, almost every human gene has a counterpart in the mouse genome. Furthermore, much of the mouse genome is syntenic with the human genome, meaning that the order of human genes and their mouse counterparts along the chromosomes is identical. This greatly facilitates the identification of genes, and allows for the study of noncoding regulatory regions by the identification of sequences conserved between mouse and human.

Noggin expression at embryonic day 13.5, visualized by staining for a lacZ transgene (blue)

Expression of Noggin (red) and Gdf5 (blue) in the forelimb, embryonic day 14.5

Ectopic expression of Noggin alters cranial morphology (right) by preventing suture fusion