Karl Oskar Illmensee (1939–)

By: Cheryl Lancaster

Karl Oskar Illmensee (1939–)

Karl Oskar Illmensee studied the cloning and reproduction of fruit flies, mice, and humans in the US and Europe during the twentieth and twenty-first centuries. Illmensee used nuclear transfer techniques (cloning) to create early mouse embryos from adult mouse cells, a technique biologists used in later decades to help explain how embryonic cells function during development. In the early 1980s, Illmensee faced accusations of fraud when others were unable to replicate the results of his experiments with cloned mouse embryos. Illmensee also worked with human embryos, investigating how embryos split to form identical twins.

Illmensee was born in Lindau, Austria, in 1939. At the Ludwig Maximilians Universität in München, Germany, he studied chemistry and biology before beginning his PhD research in the Zoologisches Institut der Universität (University Department of Zoology), part of the Ludwig Maximilians Universität. Illmensee studied the developmental genetics of fruit flies. Two other researchers, Robert Briggs and Thomas King at the American Institute for Cancer Research in Washington, USA, had cloned frogs in the 1950s. Illmensee attempted to use Briggs and King's method to clone fruit flies (Drosophila melanogaster).

Despite failing to clone an adult fly, Illmensee published the results of his research in 1968. Illmensee exchanged the nucleus of an unfertilized fly egg with a nucleus from a fertilized fly egg, a process called nuclear transplantation. Of the 118 eggs that had undergone nuclear transplantation, 11 began to develop, and one developed into the larval stage, the stage right before adulthood in fruit flies. Illmensee had not cloned an adult fly, but he had created a clone that survived to the larval stage of development. He completed his PhD in 1972.

In the early 1970s, Illmensee traveled to the Institute for Cancer Research, which later became the Fox Chase Cancer Center, in Philadephia, Pennsylvania. There, Illmensee worked with Beatrice Mintz to manipulate the unfertilized eggs (oocytes) of mice. Mintz had obtained mouse cancer cells from a malignant teratoma (teratocarcinoma cells). Mintz and Illmensee inserted those teratocarcinoma cells into early stage mouse embryos, called blastocysts. They then implanted those blastocysts into mice, which had been treated with hormones to mimic pregnancy (called pseudopregnancy). The offspring of those mice were called mosaic mice, as they inherited traits from both the cancer cells and normal cells. Offspring of mosaic mice also inherited cancerous cells, thought the mice did not develop cancer.

In 1977, Illmensee worked with Peter Hoppe on cloning mice at the Roscoe B. Jackson Memorial Laboratories in Bar Harbor, Maine. Shortly after a mouse sperm fertilizes a mouse egg, the mouse egg contains two nuclei, a maternal pronucleus from the egg, and a paternal pronucleus from the sperm. Each pronucleus contains only half of the genetic material found in the nuclei of normal cells. Together, those pronuclei combine to create the whole genome required for the embryo to develop. In their experiments, Illmensee and Hoppe removed one of the pronuclei from the fertilized mouse egg and placed the egg in a liquid that included ingredients to encourage the pronucleus to divide (cytochlasin B). The single pronucleus remaining in the egg then created a copy of itself, meaning the egg had the correct amount of genetic material required for development. Once those eggs developed into early embryos in the lab, Illmensee transferred them to pseudopregnant female mice. Illmensee and Hoppe reported seven live births out of a total of 135 manipulated eggs. Hoppe and Illmensee called those mice uni-parental, stating that the technique would enable scientists to better control and explain how embryos develop.

In 1978, Illmensee moved to become a professor at the University of Geneva in Geneva, Switzerland. Hoppe visited Illmensee at the University of Geneva during 1979 and 1980. Continuing their collaboration, Illmensee and Hoppe began to create hybrid cells, cells that contained gentic material from two different species. Hoppe and Illmensee created rat-mouse hybrid cells and human-mouse hybrid cells. Illmensee and Hoppe injected those hybrid cells into early stage mouse embryos, called blastocysts. They then transferred the blastocysts into pseudopregnant female mice, which gave birth to live mice. Mice created with rat-mouse hybrid cells produced proteins found in rats. Mice created with human-mouse hybrid cells produced proteins found in humans.

In 1981, at the University of Geneva, Illmensee and Hoppe transplanted nuclei from embryonic mouse cells into fertilized mouse eggs that lacked nuclei, a process called nuclear transfer. The eggs developed to the early blastocyst stage in the lab before being transferred to pseudopregnant female mice. Illmensee and Hoppe transplanted 179 developing eggs and recorded three live births. Later, those mice produced offspring that had traits and characteristics of the genes contained in the donated nucleus. Illmensee and Hoppe published their results, and the report attracted world-wide press attention. Following the above work, in 1981, Illmensee received the Marcel Benoist research prize for the most useful scientific discovery in Switzerland or by a Swiss national in the previous year.

In the summer of 1982, Illmensee attempted to use the nuclear transfer technique to transfer the nuclei of mouse teratocarcinoma cells into fertilized mouse eggs with their nuclei removed (enucleated). Three members of Illmensee's laboratory team, Denis Duboule, Joachim Huarte, and Kurt B¨rki, attempted to replicate Illmensee's results, but could not get their mouse nucleus and egg transplantation experiments to work. Bürki accused Illmensee of falsifying data at a University of Geneva conference in January of 1983. Bürki provided Marco Crippa, who led the biology department at the university, a report regarding his concerns about Illmensee's research. Crippa and other professors confronted Illmensee in May of 1983, and Illmensee signed a letter admitting that his work had been manipulated inappropriately or not conducted at all. The letter sparked an internal review of Illmensee's work at the University of Geneva, and a further investigation of work Illmensee had done at the Roscoe B. Jackson Memorial Laboratories.

By June 1983, the popular press reported the accusations, and other researchers began to make statements about Illmensee's work. Several researchers admitted they had attempted unsuccessfully to reproduce the results Illmensee and Hoppe had reported in 1981. For example, James McGrath and Davor Solter at the Wistar Institute of Anatomy and Biology in Philadelphia, Pennsylvania, failed to replicate Illmensee and Hoppe's work, reporting their unsuccessful results in 1984. Another group, led by Neal L. First at the University of Wisconsin in Madison, Wisconsin, also failed to reproduce Illmensee and Hoppe's results. An external review of Illmensee's research was organised by the University of Geneva in June 1983, comprised of lawyers and experts in mammalian development. Neither the Roscoe B. Memorial Laboratories nor the University of Geneva internal reviews found definitive evidence of fraud. Likewise, the external review team accepted Illmensee's version of events but conceded that Illmensee kept poor records. The external reviewers recommended that Illmensee repeat his work alongside international collaborators, starting with the transfer of mouse teratocarcinoma nuclei to enucleated fertilized mouse eggs.

In 1988, Illmensee left the University of Geneva and became professor of molecular embryology at the University of Salzburg in Salzburg, Austria. Illmensee worked on repeating the work requested by the external reviewers. In two articles published in 1989 and 1990, Illmensee repeated the required work with Jayek A. Modlinski of the University of Warsaw in Warsaw, Poland, D. Gerhäuser of the University of Geneva, and B. Lioi of the University of Naples in Naples, Italy. None of those experiments resulted in in live births. However, Illmensee stated that he had demonstrated the potential of his nuclear transfer techniques.

During the 1990s, Illmensee studied mammalian reproduction, including the biochemistry of human eggs, and the development of organs in the mouse embryo. In 1996, Illmensee became professor of reproductive medicine at the University Hospital of Innsbruck in Innsbruck, Austria.

In 2001, Severino Antinori, who studied medicine at the University of Rome La Sapienza in Rome, Italy, invited Illmensee to a cloning conference in Rome. At the conference, Illmensee met Panayiotis Zavos, who ran an artificial insemination clinic in Lexington, Kentucky. Zavos offered Illmensee a role as director of research for his company, Reprogen. Illmensee accepted Zavos's offer and began working with Reprogen in 2002. Also in 2002, Illmensee became the Austrian representative for the European Society for Human Reproduction and Embryology Advisory Committee, headquartered in Grimbergen, Belgium.

In the early 2000s, Illmensee published papers about improving artificial reproductive technology (ART) techniques. He discussed a technique called embryo splitting in mice. In the technique, half of the cells from an early embryo were removed and grown in the lab to create two embryos from one. In 2006, Illmensee and Zavos published a paper on somatic cell nuclear transfer (SCNT). SCNT involves removing a nucleus from a cell, and inserting that nucleus into another cell that has had its original nucleus removed. In their work, Illmensee and Zavos cultured cells from an infertile man in the lab. They fused a single adult cell from the infertile man with an egg from the man's wife, and allowed the egg to develop in the lab. Once the egg developed to the four-cell stage, Illmensee and Zavos transferred the early embryo to the uterus of the woman, but the pregnancy did not continue.

Speaking to journalist Sasha Karburg in 2007, Illmensee stated that he attempted to clone humans to help the many infertile couples he had met. Illmensee also said that he found cloning humans particularly difficult. Based on the difficulty he had cloning humans for therapeutic reproduction, Illmensee ended his collaboration with Zavos in May 2007.

At the Genesis Fertility Center in Patras, Greece, Illmensee began working with Mike Levanduski. They also worked at American Fertility Services in New York City, New York. Illmensee and Levanduski studied embryo splitting, a process that can occur in pregnant women and results in identical twins. Levanduski and Illmensee caused human embryos to split in the laboratory, reporting their results in 2010. As the split human embryos progressed to a further stage of development, Levanduski and Illmensee suggested that embryo splitting might be useful for artificial reproductive technologies (ART).

By 2017, Illmensee continued to work at the Genesis Fertility Center in Patras, Greece, continuing his research on ART methods.


  1. Baumgartner, Bernhard G., Karl‐Friedrich Murach, Elisabeth Schlegel, Claudia Praxmayer, and Karl Illmensee. "Comparison of Protein Analysis between Embryonic and Extraembryonic Tissues during the 11th Day of Gestation of the Mouse." Electrophoresis 15 (1994): 992–1000.
  2. Bergant, Anton M., Kurt Heim, Hanno Ulmer, and Karl Illmensee. "Early Postnatal Depressive Mood: Associations with Obstetric and Psychosocial Factors." Journal of Psychosomatic Research 46 (1999): 391–4.
  3. Briggs, Robert, and Thomas King. "Transplantation of Living Nuclei from Blastula Cells into Enucleated Frogs' Eggs." Proceedings of the National Academy of Sciences of the United States of America 38 (1952): 455–63. http://www.pnas.org/ content/38/5/455.long (Accessed May 16, 2016).
  4. Briggs, Robert, and Thomas J. King. "Nuclear Transplantation Studies on the Early Gastrula (Rana pipiens): I. Nuclei of Presumptive Endoderm." Developmental Biology 2 (1960): 252–70.
  5. Cooke, Robert. "Female Mice Give Birth – With No Help from Males." Boston Sunday Globe, January 4, 1982.
  6. Hoppe, Peter C. "Microsurgical Manipulation of Mouse Eggs." in The International Committee, ed. The Jackson Laboratory: 37–38. The Jackson Laboratory Archives, Bar Harbor, Maine, The Joan Staats Library.
  7. Hoppe, Peter C., and Karl Illmensee. "Microsurgically Produced Homozygous-Diploid Uniparental Mice." Proceedings of the National Academy of Sciences of the United States of America 74 (1977): 5657–61. http://www.pnas.org /content/74/12/5657.long (Accessed May 16, 2016).
  8. Illmensee, Karl. "Transplantation of Embryonic Nuclei into Unfertilized Eggs of Drosophila melanogaster." Nature 219 (1968): 1268–9.
  9. Illmensee, Karl. "Experimental Genetics of the Mouse Embryo." Progress in Clinical and Biological Research 85 (1982): 87–102.
  10. Illmensee, Karl. "Controversy over the Cloning of Mice." Nature 398 (1999): 19–20.
  11. Illmensee, Karl, and Peter C. Hoppe. "Nuclear Transplantation in Mus musculus: Developmental Potential of Nuclei from Preimplantation Embryos." Cell 23 (1981): 9–18.
  12. Illmensee, Karl, and Anthony P. Mahowald. "Transplantation of Posterior Polar Plasm in Drosophila. Induction of Germ Cells at the Anterior Pole of the Egg." Proceedings of the National Academy of Sciences of the United States of America 71 (1974): 1016–20. http://www.pnas.org/ content/71/4/1016.long (Accessed May 16, 2016).
  13. Illmensee, Karl, and Anthony P. Mahowald. "The Autonomous Function of Germ Plasm in a Somatic Region of the Drosophila Egg." Experimental Cell Research 97 (1976): 127–40.
  14. Illmensee, Karl, and Beatrice Mintz. "Totipotency and Normal Differentiation of Single Teratocarcinoma Cells Cloned by Injection into Blastocysts." Proceedings of the National Academy of Sciences of the United States of America 73 (1976): 549–53. http://www.pnas.org/ content/73/2/549.long (Accessed May 16, 2016).
  15. Illmensee Karl, Peter C. Hoppe, and Carlo M. Croce. "Chimeric Mice Derived from Human-Mouse Hybrid Cells." Proceedings of the National Academy of Sciences of the United States of America 75 (1978): 1914–8. http://www.pnas.org/ content/75/4/1914.long (Accessed May 16, 2016).
  16. Illmensee, Karl, D. Gerhäuser, B. Lioi, and Jacek A. Modlinski. "Developmental Potential of Nuclei from Mouse Teratocarcinoma Cells." Naturwissenschaften 76 (1989): 582–4.
  17. Illmensee, Karl, Mike Levanduski, Andrea Vidali, Nabil Husami, Vasilios T. Goudas. "Human Embryo Twinning with Applications in Reproductive Medicine." Fertility and Sterility 93 (2010): 423–7.
  18. Karberg, Sasha. "I've Cloned Human Embryos." Magazin P.M., October 1, 2007.
  19. King, Thomas J., and Robert Briggs. "Changes in the Nuceli of Differentiating Gastrula Cells, as Demonstrated by Nuclear Transplantation." Proceedings of the National Academy of Sciences of the United States of America 41 (1955): 321–5. http://www.pnas.org/ content/41/5/321.long (Accessed May 16, 2016).
  20. Kolata, Gina B. Clone: The Road to Dolly and the Path Ahead. The Penguin Press: London, 1997.
  21. Lewis, Ricki A. Discovery: Windows on the Life Sciences. Abingdon: Blackwell Science Inc., 2001.
  22. MacKenzie, Debora. "New Charges Hit Illmensee." New Scientist, May 31, 1984: 3–4. https://books.google.com/books ?id=IFqxBJNuET8C&pg=PA3&lpg=PA3&dq= MacKenzie,+Debora.+%E2%80%9CNew+Charges+Hit+Illmensee.%E2%80%9D++New+ Scientist&source=bl&ots=xtUmRkcYxr&sig=eSjvgyd- g2GkeA4Cd20hyXJJE-Q&hl= en&sa=X&ved=0ahUKEwi5oP2g-9_MAhVQyGMKHVKHDWkQ6AEIJTAC#v= onepage&q= MacKenzie%2C%20Debora.%20%E2%80%9CNew%20Charges%20Hit%20Illmensee.%E2% 80%9D%20%20New%20Scientist&f=false (Accessed May 16, 2016).
  23. Maienschein, Jane. Whose View of Life? Embryos, Cloning and Stem Cells. Cambridge: Harvard University Press, 2003.
  24. Marx, Jean L. "Swiss Research Questioned." Science 220 (1983): 1023. http://science.sciencemag.org/content/220/4601/1023.long (Accessed February 26, 2017).
  25. Marx, Jean, L. "Bar Harbor Investigation Reveals No Fraud." http://science.sciencemag.org/content/220/4603/1254.1.long (Accessed February 26, 2017). Science 220 (1983): 1254.
  26. McGrath, James, and Davor Solter. "Inability of Mouse Blastomere Nuclei Transferred to Enucleated Zygotes to Support Development In Vitro." Science 226 (1984): 1317–9.
  27. Mintz, Beatrice, and Karl Illmensee. "Normally Genetically Mosaic Mice Produced from Malignant Teratocarcinoma Cells." Proceedings of the National Academy of Sciences of the United States of America 72 (1975): 3538–9. http://www.pnas. org/content/72/9/3585.full.pdf (Accessed May 16, 2016).
  28. Modlinski, Jacek A. "Transfer of Embryonic Nuclei to Fertilized Mouse Eggs and Development of Tetraploid Blastocysts." Nature 273 (1978): 466–7.
  29. Modlinski, Jacek A, D. Gerhäuser, B. Lioi, H. Winking, and Karl Illmensee. "Nuclear transfer from teratocarcinoma cells into mouse oocytes and eggs." Development 108 (1990): 337–348. http://dev.biologists.org/content/develop/108/2/337.full.pdf (Accessed February 26, 2017).
  30. Papaioannou, Virginia E., Michael W. McBurney, Richard L. Gardner, and Martin J. Evans. "Fate of Teratocarcinoma Cells Injected into Early Mouse Embryos." Nature 258 (1975): 70–3.
  31. Prather, Randall S. "Nuclear Transplantation and Embryo Cloning in Mammals." Institute for Laboratory Animal Research Journal 33 (1991): 62–8. http://ilarjournal.oxfordjournals.org/content/33/4/62.full.pdf+ html (Accessed May 16, 2016).
  32. Prather, Randall S., Frank L. Barnes, Michelle M. Sims, Jim M. Robl, Willard H. Eyestone, and Neal L. First. "Nuclear Transplantation in the Bovine Embryo: Assessment of Donor Nuclei and Recipient Oocyte." Biology of Reproduction 37 (1987): 859–66. http://www. biolreprod.org/content/37/4/859.long (Accessed May 16, 2016).
  33. Praxmayer, Claudia, Karl-Friedrich Murach, Bernhard Baumgartner, Friedrich Aberger, Elisabeth Schiegel and Karl Illmensee. "Protein Synthesis in Murine Organs during Postimplantation Development Detected by Two-Dimensional Gel Electrophoresis." Electrophoresis 13 (1992): 720–2.
  34. Sanford, Barbara H. "Dr. Karl Illmensee [memorandum]." The Jackson Laboratory Archives, Bar Harbor, Maine, The Joan Staats Library.
  35. Schmeck Jr., Harold M. "Panel Questions Embryo Research." The New York Times, June 4, 1983. http://www.nytimes.com/1983/06/04/us/panel-questions-embryo-research. html (Accessed May 16, 2016).
  36. "Scientist Credited with Pioneering Cloning Accused of Faking Research." The Nashua Telegraph, May 26, 1983. https://news. google.com/newspapers?nid=2209&dat=19830526&id= saYrAAAAIBAJ&sjid=6PwFAAAAIBAJ&pg=6707,5922240&hl=en (Accessed May 16, 2016).
  37. "Scientists Develop Potential Mammal-Cloning Techniques." The Wall Street Journal, January 5, 1981.
  38. Spitzer, D., Karl Friedrich Murach, Friedrich Lottspeich, Alfons Staudach, and Karl Illmensee. "Different Protein Patterns Derived from Follicular Fluid of Mature and Immature Human Follicles." Human Reproduction (1995): 798–807. http://humrep.oxfordjournals.org/content/11/4/798.full.pdf+html (Accessed May 16, 2016).
  39. Stevens, Leroy C., and Don S. Varnum. "The Development of Teratomas from Parthenogenetically Activated Ovarian Mouse Eggs." Developmental Biology 27 (1974): 369–80.
  40. Sullivan, Walter. "First Cloning of Mammals Produces 3 Mice." The New York Times, January 4, 1981. http://www.nytimes.com/1981/01/04/us/first-cloning-of-mammals-produces -3-mice.html (Accessed May 16, 2016).
  41. Sullivan, Walter. "Letter and Article Proof to Peter Hoppe" [letter] (1982). The Jackson Laboratory Archive, Bar Harbor, Maine, The Joan Staats Library.
  42. Tarkowski, Andrzej K. "Induced Parthogenesis in the Mouse." In The Developmental Biology of Reproduction, eds. Clement L. Markert and John Papaconstantinou. Cambridge: Academic Press, 1975.
  43. The Jackson Laboratory. "Goings and Comings." JAX (1980): 2.
  44. The Jackson Laboratory. "After Nuclear Transplant Success Dr. Hoppe Plans New Avenues of Research." JAX 27 (1981): 1, 3.
  45. Vithoulkas, Alexandrou, Mike Levanduski, Vasilios T. Goudas, and Karl Illmensee. "Growth Factors Associated with Embryo Co-Culture and Clusters Compared to Regular Embryo Culture in IVF." Fertility and Sterility 102 (2014): e218. http://www.fertstert.org/article/S0015-0282%2814%2901362-4/pdf (Accessed May 16, 2016).
  46. Wilmut, Ian, Keith Campbell, and Colin Trudge. The Second Creation: Dolly and the Age of Biological Control. Cambridge: Harvard University Press, 2001.
  47. Witkowska, Anna. "Parthenogenetic Development of Mouse Embryos In Vivo: II. Postimplantation Development." Journal of Embryology and Experimental Morphology 30 (1973): 547–60. http://dev.biologists.org/content/develop/30/3/547.full.pdf (Accessed May 16, 2016).
  48. Zavos, Panayiotis, and Karl Illmensee. "Possible Therapy of Male Infertility by Reproductive Cloning: One Cloned Human 4-Cell Embryo." Archives of Andrology: Journal of Reproductive Systems 52 (2006): 243–54.



Carolina J. Abboud

How to cite

Lancaster, Cheryl, "Karl Oskar Illmensee (1939–)". Embryo Project Encyclopedia ( ). ISSN: 1940-5030 https://hdl.handle.net/10776/11431


Arizona State University. School of Life Sciences. Center for Biology and Society. Embryo Project Encyclopedia.

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