Overview

Martin J. Evans (born 1 January 1941 in Stroud, Gloucestershire) is a British geneticist whose laboratory discoveries established key methods for manipulating the mammalian genome. Evans's work on deriving and maintaining embryonic mouse embryonic stem cells and on applying homologous recombination in those cells made targeted alteration of animal genomes practical for research and medicine.

Early breakthrough: embryonic stem cells

In collaboration with Matthew Kaufman, Evans reported robust conditions to isolate pluripotent cells from early mouse embryos. These cultured cells could self-renew in vitro and differentiate into many cell types, providing a reproducible cellular resource for developmental studies and for genetic manipulation of mammals. The availability of stable embryonic stem cell lines was a prerequisite for later methods that introduce specific genetic changes and then transmit them through the germline.

Gene targeting, knockout mice and the Nobel Prize

Evans, together with Oliver Smithies and Mario Capecchi, helped to establish and apply the principle that introduced DNA with sequence similarity to a chromosomal locus can undergo homologous recombination with the resident gene. That principle underlies modern genetic engineering techniques known as gene targeting. When gene targeting is performed in embryonic stem cells and those cells contribute to the germline of a resulting animal, researchers can produce defined genetic alterations such as knockout mice. For these achievements the three scientists shared the Nobel Prize in Physiology or Medicine in 2007.

Method in brief

Derivation of mouse embryonic stem cells typically begins with the inner cell mass of a blastocyst-stage embryo. Cells are plated and maintained under conditions that preserve pluripotency, historically using supportive feeder layers and factors that prevent differentiation. To make a targeted change, researchers introduce a DNA construct designed to match a genomic region but carrying a deliberate modification. Cellular repair machinery can replace the endogenous sequence with the altered one through homologous recombination. Selected and screened stem cell clones carrying the change are then used to generate animals that transmit the modification to offspring.

Creating genetically altered animals

The combination of cultured pluripotent cells and targeted recombination enabled production of chimeric animals and, ultimately, fully gene-modified lines. Knockout animals—organisms in which a specific gene has been disrupted—became a routine experimental class for assigning gene function, modeling human disease and testing therapies. These approaches remain a foundation for experimental genetics even as newer editing tools have appeared.

Applications and wider impact

  • Generation of animal models for human diseases, including cancer, metabolic and neurological disorders.
  • Functional dissection of developmental processes, enabling researchers to link genetic changes to phenotypes.
  • Preclinical testing and validation of drug targets using genetically defined animal strains.
  • Conceptual groundwork for subsequent advances such as induced pluripotent stem cells and programmable nucleases.

Ethical and scientific considerations

Evans's work prompted wide discussion about the ethical use of embryos, animal welfare, and the regulation of genetically modified organisms. Those debates influenced research governance, laboratory practice and public policy in many countries. At the same time, the technical clarity provided by embryonic stem cell culture and gene targeting improved experimental reproducibility and spurred a broad expansion of biomedical research.

Legacy and later developments

While genome-editing platforms such as CRISPR have increased speed and accessibility of targeted changes, the experimental strategy pioneered by Evans—cultured pluripotent cells plus sequence-specific modification via homologous recombination—remains central to genetic research. Evans's contributions are often discussed alongside those of his collaborators, including Oliver Smithies and Mario Capecchi, and underpin many subsequent advances in genetic engineering and in the production of model organisms for study.

For concise background on related topics and figures, see entries on gene targeting, the science of homologous recombination, and summaries of knockout mice and their role in studying animal genomes.