A new tool called MiMIC (Minos-mediated integration cassette) developed by researchers at Baylor College of Medicine in the Jan and Dan Duncan Neurological Research Institute at Texas Children’s Hospital is the "Swiss army knife" of the fruit fly laboratory, enabling scientists to tackle an array of important questions with a simple construct.

The technique, built on the unusual characteristics of transposons or "jumping genes," that can be used in a host of different ways – to "tag" genes of interest, "trap" genes and control gene expression, among others. A report on the work appears in the current issue of the journal Nature Methods. (Transposons are short pieces of DNA that can move from one location in the DNA molecule to another, inserting themselves into other parts of the genome – hence the name jumping genes).

Efficient tool

"You can use MiMIC to replace any piece of DNA (genetic material) with any other piece of DNA efficiently," said Dr. Hugo Bellen, professor of molecular and human genetics at BCM, a member of the Neurological Research Institute and director of the Program in Developmental Biology. "It was surprising that it is such an efficient tool. We can now tag proteins quickly and these tags do not seem to obviously affect the function of proteins in a significant way."

The tool is the brainchild of Dr. Koen Venken, a postdoctoral researcher in Bellen's laboratory. To build MiMIC, Venken started with Minos, a transposon already used in Drosophila research. He added a gene trap cassette, which enables inactivation of a particular gene at the site at which the transposon is inserted.

MiMIC also includes a marker for yellow body color flanked by two attP sites that enable replacement of the DNA sequence in the middle with any other DNA sequence. "It’s all based on RMCE (recombinase-mediated cassette exchange)," said Venken. This technique allows the clean exchange of a DNA cassette in vivo (a DNA cassette is a module of genetic material that contains one or more genes.)

That is the beauty and simplicity of this technique. "It saves a lot of money and time," said Venken. The system can be used in live insects.

Limitless gene modification

The development was prompted when a collaboration called the Drosophila Gene Disruption Project was trying to create transposon insertions in most fruit fly genes, said Bellen, who is also a Howard Hughes Medical Institute investigator. This new transposon is much more effective than those that were previously used because a single insertion in a gene permits numerous different manipulations of the gene in which the MiMIC is inserted. In summary, MiMIC allows almost limitless gene modification and genome engineering, he said.

Others who took part in this work include: Karen L. Schulze, Nele Haelterman, Hongling Pan and Yuchun He of BCM; Martha Evans-Holm, Joseph W. Carlson and Roger A. Hoskins of Lawrence Berkeley National Laboratory in Berkley, California and Robert W. Levis and Allan C. Spradling of the Carnegie Institution for Science in Baltimore, Maryland.

Funding for this work came from the National Institutes of Health and the Howard Hughes Medical Institute.

Bellen holds the March of Dimes Chair in Developmental Biology and Charles Darwin Chair in Genetics and is a Howard Hughes Medical Institute Investigator.