What Are Transgenic Mice and Why Are They Important in Genetic Research?
When considering the drugs we take to alleviate the symptoms of disease, never would we have imagined how important transgenic laboratory mice are to drug development. However, these mice are of pivotal importance in the genetic research necessary to achieve the relief we hope for. Cancer, Alzheimer’s disease, inherited disorders and a variety of rare, genetic conditions are more treatable today than ever before, as a result of breakthroughs originally studied in transgenic mice.
Understanding Transgenic Models and Their Importance
In order to understand transgenic mice, it is first necessary to understand the transgene. Transgenes are genes that have been taken from one organism and transferred to the genetic makeup of another. For example, a human gene can be copied and transferred to the genetic makeup of a mouse in order to study human disease in a model biological system. The most common methods of introducing a transgene into an animal model involve genetic manipulation of some sort, such as by pronuclear injection of embryos or by homologous recombination in cells. As a result, the use of genetically enhanced transgenic mice has become a crucial part of the science behind elucidating human disease.
Genetic Manipulation History and Transgenes
Before the technology became available to do direct genetic manipulations in animals, selective breeding was used as a means of studying specific genes by selecting and breeding for animals that contained the specific gene of interest. This trend changed however in the 1970’s with the work of Rudolf Jaenisch and the production of the first transgenic mouse where foreign DNA was successfully inserted into early-stage mouse embryos, resulting in mice that carried the modified gene in all their tissues.
How Is a Transgene Obtained?
Two basic approaches exist for creating transgenic mice. The first involves delivery of the transgene into a single cell of the mouse embryo via pronuclear injection. Through this method, researchers can overexpress new genes, effectively creating a transgenic mouse. The second method is through the modification of embryonic stem cells via homologous recombination, and the injection of the targeted ES cells into mouse blastocysts.
Transgenic Mouse Technologies
In recent years, scientists have been trying to improve the technologies for obtaining transgenic mouse models. One more recent development is that of CRISPR-Cas9, a relatively new system that can be used to produce accurately targeted changes into mouse embryos without the need for targeting ES cells first.