In addition, ES cells grown in the lab can be used to make knockout mice as long as 10 years after they were harvested. ES cells are used because they are able to differentiate into nearly any type of adult cell, which means that if a gene is knocked out in an ES cell, the effects can be observed in any tissue in an adult mouse. Researchers begin by harvesting embryonic stem (ES) cells from early-stage mouse embryos four days after fertilization. Such studies will accelerate efforts to translate newfound knowledge of the human and mouse genomes into better strategies for diagnosing, treating and preventing human disease. However, when the p53 gene is knocked out in mice, the animals develop tumors in a different array of tissues.Despite these drawbacks, knockout mice offer one of the most powerful means now available for studying gene function in a living animal. For example, mutations in the p53 gene are associated with more than half of human cancers and often lead to tumors in a particular set of tissues. Knocking out a gene also may fail to produce an observable change in a mouse or may even produce different characteristics from those observed in humans in which the same gene is inactivated.
In some instances, the gene may serve a different function in adults than in developing embryos. The lack of adult mice limits studies to embryonic development and often makes it more difficult to determine a gene's function in relation to human health. About 15 percent of gene knockouts are developmentally lethal, which means that the genetically altered embryos cannot grow into adult mice. While knockout mice technology represents a valuable research tool, some important limitations exist. For example, "Methuselah" is a knockout mouse model noted for longevity, while "Frantic" is a model useful for studying anxiety disorders. Humans born with mutations that inactivate the p53 gene suffer from Li-Fraumeni syndrome, a condition that dramatically increases the risk of developing bone cancers, breast cancer and blood cancers at an early age.Other mouse models are named, often with creative flair, according to their physical characteristics or behaviors. For example, the p53 knockout mouse is named after the p53 gene, which codes for a protein that normally suppresses the growth of tumors by arresting cell division. Many of these mouse models are named after the gene that has been inactivated. Knockout mice also offer a biological context in which drugs and other therapies can be developed and tested. Consequently, observing the characteristics of knockout mice gives researchers information that can be used to better understand how a similar gene may cause or contribute to disease in humans.Įxamples of research in which knockout mice have been useful include studying and modeling different kinds of cancer, obesity, heart disease, diabetes, arthritis, substance abuse, anxiety, aging and Parkinson disease. Knocking out the activity of a gene provides valuable clues about what that gene normally does.
0 kommentar(er)
