Evans, Sir Martin John (1941-…), a British geneticist, won the 2007 Nobel Prize in physiology or medicine for his contribution to a technique used to modify genes in mice. Genes direct the formation, growth, and reproduction of living cells and organisms. Evans shared the prize with the American biologists Mario R. Capecchi and Oliver Smithies. The three scientists developed methods used to produce knockout mice, strains of laboratory mice in which a particular gene has been inactivated or “knocked out.” Scientists use knockout mice as models for studying gene function and disease.
In the early 1980’s, working independently, Capecchi and Smithies developed a technique called gene targeting. The two men had demonstrated that gene targeting could be used to knock out genes within individual mammalian cells. Around the same time, Evans developed a technique that could be combined with gene targeting to allow scientists to knock out genes throughout an entire organism.
Evans began with mouse embryos. Early in development, such an embryo consists of a hollow ball of cells called a blastocyst. The blastocyst contains stem cells, cells that have the ability to develop into any of the various types of cells found in an adult mouse. Evans removed stem cells from mouse blastocysts and introduced to them a mutated form of a specific gene. This gene could only be passed from mother to son. He then injected the modified stem cells back into the blastocysts. Evans did not use gene targeting to introduce the mutated genes, but instead he used a technique that uses special viruses called retroviruses to introduce genes into the cells. Some cells in the blastocysts contained the original version of the gene while the injected cells contained the mutated version. The blastocysts Evans created were genetic chimeras that have a mix of cell types in a single individual (see Chimera ). Some of the blastocysts developed into female mice. When the females mated, some of their male offspring inherited the mutated gene in all of their cells. Evans had demonstrated that embryonic stem cells could be used to transmit a modified gene into mice. However, the retroviral technique only allowed scientists to add certain genes, rather than “knockout” the gene of their choosing.
Many scientists, including Capecchi, Smithies, and Evans, quickly realized that gene targeting could be used in combination with Evans’s embryonic stem cell discoveries to alter or inactivate any gene. In 1989, several groups published research announcing the creation of the first knockout mice. Scientists have used knockout mice to study many diseases, including cystic fibrosis, diabetes, and hypertension, and to analyze the role of various genes in development.
Martin John Evans was born in Stroud, England, on Jan. 1, 1941. He studied biochemistry at Cambridge University, graduating in 1963, and received his Ph.D. degree in anatomy and embryology at University College London in 1969. He remained at University College as a lecturer until 1978 and held positions at Cambridge University from 1978 to 1999. Since 1999, he has been professor of mammalian genetics at Cardiff University in Wales. He was knighted in 2004.
See also Capecchi, Mario Renato ; Smithies, Oliver .
