Back in the 1940s, US biologist Barbara McClintock discovered an amazing phenomenon: certain DNA particles have the ability to jump from one spot of a chromosome to another. One such DNA element, isolated from fruitflies by University of Crete researchers, was recently shown to be able to jump into human genes as well, making it a potentially powerful tool for exploring the human genome.
The DNA element, named Minos after Crete's mythological King Minos, was discovered in 1991 at Crete's Insititute of Molecular Biology and Biotechnology (IMBB) by the research team of Professor Charalambos Savakis working at the Medical School of the University of Crete.
Originally isolated from the DNA of the fruitfly species Drosophila hydei, Minos has since been shown to have the ability to cut and paste itself not only within its own chromosomes but also those of a variety of other insect species, including the mosquito (Anopheles stephensi) the silkworm, (Bombyx mori) the fruitfly, (Drosophila melanogaster) and the Mediterranean fruit fly or medfly (Ceratitis capitata).
Genetic leaps
Called "transposable elements" or jumping genes, these snippets of DNA are able to jump because they contain a gene for an enzyme called "transposase". The enzyme cuts the element out from its original site and re-inserts it at another point elsewhere in the genome. Thus, by incorporating another gene within the transposable element (now called a "complex transposon"), biologists are able to use it to transfer genes from one organism to another. When a gene is inserted into an organism using this technique, that organism is said to be "transformed".
In 1995, in the first successful attempt to transform a non-Drosophila species, Savakis team used Minos to insert a gene for white eyes into the Mediterranean fruit fly, a major agricultural pest worldwide. This was an important advance because the ability to manipulate the genes of harmful species, such as the medfly or the malaria-carrying mosquito, can prove extremely valuable. In a paper published last November in the journal EMBO Reports, Savakis and his colleagues showed that Minos is equally at home jumping inside the human genome, as proven by their successful attempts to transfer Minos elements into human cells. Their experiments prove that Minos is potentially capable of inserting itself in all the genes in the human genome, thus helping to determine their functions.
Gene traps
In the IMBB experiments, Minos was combined with a reporter gene coding for a particular biochemical substance. When the transposon incorporating a reporter gene inserts itself on a chromosome next to a gene that is active, the reporter gene too becomes activated, leading to the production of this substance, which can then be detected by researchers.
This technique, called gene trapping, can help researchers determine which genes do what and when. When a transposable element with a reporter gene pastes itself into a gene whose function is unknown, investigators tracking the production of the biochemical substance produced by the reporter gene can determine when that particular gene being studied is active, e. g. during embryonic development, fighting disease, and subsequently what it codes for. Although transposable elements have previously been used for gene trapping in other complex organisms, the Savakis teams effort represents the first time this has been done in mammals.
In view of the potential importance of Minos in the biotech industry, Savakis along with Frank Grosveld, a professor at Erasmus University in Holland, and Roger Craig, former director of Biotechnology at Imperial Chemical Industries (ICI), have formed Minos Biosystems Ltd, a company which will control the intellectual property rights to Minos.
