- Międzygórze, Lower Silesian Voivodeship, Poland
- Associated organizations
- MIT, U.S. National Academy of Sciences, American Academy of Arts and Sciences, International Society for Stem Cell Research
- Fields of study
- Biology, Biochemistry, Transgenic Research
- Otto Warburg Medal, Wolf Prize in Medicine, Massry Prize from the Keck School of Medicine, Max Delbrück Medal, Robert Koch Prize, Gruber Prize in Genetics, Boehringer Mannheim Molecular Bioanalytics Prize, National Medal of Science
Rudolf Jaenisch is a biology researcher who was the first person to create a transgenic animal. This procedure had sparked further developments within the fields of biological and genetic engineering, as this process is used to add specific genetic traits to an organism via artificial inclusion. He is currently serving as a biology professor at the Massachusetts Institute of Technology.
Jaenisch was born on April 20th, 1942 in Międzygórze, Lower Silesian Voivodeship in Poland. He had came from a family of German physicians, and like his father and grandfather, was expected to attend medical school. Despite attending medical school and enjoying it, he didn't feel comfortable with the ways in which it was taught and soon lost interest . Seeking to find something he found interest in, Jaenisch began to attend the Max Planck Institute of Biochemistry at Martinsried in Germany to do biological research while continuing his M.D. degree.
Doing research into bacteriophages, Jaenisch enjoyed it immensely and found that he had a passion in research. Joining one of the leading professors in the development of phages, P. H. Hofschneider allowed Jaenisch to join his team of researchers. He went on to complete his medical school thesis on the phage replication and expression within bacteria. Eventually, Jaenisch went on to graduate in 1967 with his M.D.
After completing two additional years of experimentation at the Max Planck Institute at the University of Munich, he choose to travel to the United States to pursue postdoctoral training. Searching for a mentor in his work, he found geneticist Arnold Levine, who had recently set up his first laboratory within Princton University. As a result, Levine is credited for being a major inspiration to Jaenisch's research later on within his career. Jaenisch was Levine's first postdoc and had a significant amount of trust within him, and three weeks into the program Levine had traveled to Europe and allowed Jaenisch to run the lab. It was surprising to Jaenisch that Levine would allow him to run the lab by himself at such an early stage, but as a result he not only built experience as an independent researcher, but also noted the time he spent with Levine was key to his overall career development.
In 1974 during his time spent at Levine's laboratory, Jaenisch had begun to research mammalian cells infected with the simian virus (SV40); a pathogen known to cause tumors within connective tissue. With the help of graduate students, Jaenisch continued to research the effects and replication of the SV40 virus, trying to find deeper meaning into the spread of SV40 . During his research he had stumbled upon an article by developmental geneticist Beatrice Mintz at the Fox Chase Cancer Center on generating chimeric mice. From reading the article, Jaenisch had suddenly questioned if early developing embryo's would be affected by the cancerous effects of the SV40.
Wanting to propose the idea of injecting the SV40 into mice embryo Janeisch, under the account that his mentor was in Europe at the time, traveled to the Fox Chase Cancer Center to contact Mintz and propose the idea. After much skepticism and careful planning, Jaenisch was given the opportunity to practice the experiment in at the Fox Chase Cancer Center, and while at the grace of Levine, continue half the research in his laboratory . In an interview with Jaenisch on the creation of the first transgenic organism, he credits Mintz as one of the major influences that led to its development. 
During his time researching with Mintz and Levine, Jaenisch had accepted a position at the Salk Institute for Biological Studies in California, where he began to collaborate with fellow researcher Paul Berg in detecting SV40 within the viral DNA of mice. In 1974, using a technique known as nick translation which takes a piece of radioactive DNA and subsequently marks it into an organism in order to trace its development, found that when the SV40 was injected into the embryo that it had fully incorporated itself into the tissue of the mouse without causing cancer. Jaenisch eventually became ecstatic, as he discovered that the SV40 had fully incorporated itself into the genome of the mice embryo; as a result, the first transgenic organism was born from the merging of mouse and SV40 DNA.
In 1977 Jaenisch went on to the Heinrich Pette Institute in Hamburg, Germany to study viral infection on mice. The research led him to investigate DNA methylation, which played a role in silencing gene activity during early development. After seven more years, he traveled back to the United States to work at the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, where he studied epigenetics and understanding how DNA methylation controls gene expression. From there in 1996, following the birth of the cloned Dolly the Sheep, Jaenisch set out to try to understand how a fully differentiated nucleus from an adult cell that had been placed inside an enucleated egg could be changed by the egg’s cytoplasm. Eventually in 2007 he became one of the first researchers to identify master gene regulators that effectively reprogram adult cells. Today, he currently serves as a biology professor at the Massachusetts Institute of Technology.