Knockout mouse

Knockout mouse refers to a laboratory mouse genetically engineered to have one or more of its genes made inoperative, known as a gene knockout. This process allows researchers to study the gene's function by observing the differences between the knockout mice and those with the gene intact. The creation and study of knockout mice have become fundamental in biomedical research and have contributed significantly to our understanding of gene function, particularly in relation to human diseases.

Overview

The concept of the knockout mouse was first introduced in the 1980s, revolutionizing genetic research. By selectively disabling specific genes, scientists can mimic human genetic conditions, making knockout mice invaluable models for studying a wide range of diseases, including cancer, heart disease, diabetes, and neurological disorders. The technique involves targeting a specific gene and disrupting its normal function through a process called homologous recombination in embryonic stem cells. These modified cells are then injected into mouse blastocysts, which are implanted into surrogate female mice. The offspring that inherit the modified gene are the knockout mice.

Methodology

The creation of a knockout mouse involves several key steps:

1. Gene Targeting: A targeting vector is designed to contain a piece of DNA that is homologous to the target gene but includes a selectable marker gene, usually conferring resistance to a particular antibiotic, and a reporter gene.
2. Homologous Recombination: The targeting vector is introduced into mouse embryonic stem (ES) cells, where it replaces the normal gene through homologous recombination.
3. Selection: Cells that have successfully integrated the targeting vector are selected using the marker gene.
4. Generation of Chimeric Mice: The modified ES cells are injected into mouse blastocysts, which are then implanted into surrogate mothers. The resulting offspring are chimeric, containing a mix of cells from both the modified ES cells and the blastocyst.
5. Breeding: Chimeric mice are bred to produce offspring that are homozygous for the knockout gene, meaning both copies of the gene are knocked out.

Applications

Knockout mice have a wide range of applications in medical and biological research. They are used to:

• Study the role of specific genes in health and disease.
• Model human diseases to understand their mechanisms and to develop new treatments.
• Investigate the complex interactions between genes.
• Assess the safety and efficacy of new drugs.

Ethical Considerations

The use of knockout mice in research raises several ethical considerations. The welfare of the animals is a primary concern, and researchers must follow strict guidelines to ensure that the mice are treated humanely. Additionally, the implications of genetically modifying organisms, including potential impacts on natural ecosystems, must be carefully considered.

Future Directions

Advancements in gene editing technologies, such as CRISPR-Cas9, are making the creation of knockout mice faster, cheaper, and more precise. These developments are expected to expand the use of knockout mice in research, leading to new discoveries in genetics and medicine.

See Also

• Genetically modified organism
• Gene therapy
• CRISPR
• Model organism