What Are Transgenic Mice and Why Are They Important in Genetic Research?
When considering the drugs we take to alleviate the symptoms of, or even cure certain diseases entirely, transgenic mice bred in a lab are not always what we first think of. However, these mice are of pivotal importance in the genetic research necessary to achieve the results 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 in genetic manipulation.
Understanding Transgenic Models and Their Importance
In order to understand what transgenic mice are all about, it is first necessary to understand the transgene. Transgenes are essentially genes that have been copied from one organism and tied to the genetic makeup of another. The development of a transgene can be performed through natural means – such as selective breeding – or through the use of a number of artificial methods. The most common methods involve genetic manipulation of some sort, and are most importantly used today in fields such as genetic therapy and the treatment of diseases such as cancer, HIV, leukemia, immunodeficiencies and various genetic disorders. As a result, the use of genetically enhanced, humanized mice, for the purpose of studying these diseases, has become a crucial part of the science behind modern medicine.
Genetic Manipulation History and Transgenes
The idea of selective breeding is a very old one, and has been actively considered in the collective consciousness of the scientific community, for genetic purposes, since the late 19th century. Transgenic mice, however, have only been around for a few decades, since the technology did not permit such a level of artificial genetic manipulation until that time. The 1970s and 1980s have seen scientists pushing the boundaries of what is possible by combining the DNA of two or more very different organisms. Genetic engineering methods were used for that purpose, and the result was named the production of so-called transgenes. Although the first transgenic organisms date back to the work of Annie Chang in 1974, the incorporation of transgenes into retroviruses and their injection into larger organisms only came later.
How Is a Transgene Obtained?
Two basic approaches exist to the creation of genetically modified, transgenic mice. The first is to deliver the transgene into a single cell of the mouse embryo with the help of a pronuclear injection. Through this method, researchers can opt to either overexpress certain genes or introduce new genetic material, effectively creating a transgenic mouse. The second method is through the modification of embryonic stem cells, involving the injection of homologous DNA sequences into the mouse blastocysts.
Transgenic Mouse Technologies
Recent years have found scientists trying to perfect the use and development of new technologies for obtaining transgenic mouse models. One of these is CRISPR-Cas9, a relatively new system that can be programmed to induce accurately targeted changes into the mouse genome. There are several other technologies as well, including the development of artificial retroviral infections, as well as the direct microinjectioin of modified DNA into fertilized one-cell mouse embryos. The latter method of obtaining transgenic mice typically involves the use of genomic PCR assay or a Southern blot to identify the founders present in pseudo-pregnant foster mothers.