"We know how many genes are in the mammalian genome, but that does not tell us how they carry out their jobs," said senior author Tian Xu, Professor and Vice Chair of Genetics at Yale University School of Medicine and a Howard Hughes Medical Institute Investigator. "We have found a way to systematically inactivate genes in the mouse genome so we can understand the functions of these genes."

Xu and his colleagues at Fudan University in Shanghai, China finally chose a transposon called piggyBac that was originally identified in the cabbage looper moth. They discovered that it was stable and versatile in mouse and human cell lines , providing a new way to genetically manipulate mammalian cells. It also worked in mice even when it carried a couple of extra genes.

Xu's team made it easier to see the genes piggyBac associates with by adding a red fluorescent protein and an enzyme that changes the coat colour of a white mouse to grey or black. The genes carried by the transposons have been stably inherited and expressed through five generations.

"The transposon acts as a genetic beacon, so researchers can easily track its location without having to sequence the entire genome," said Xu. In their experiments, piggyBac incorporated into many chromosomes in human and mouse cells. PiggyBac can be removed from a mouse lineage by breeding with another mouse that has the enzyme to excise the transposon.

This technique is a powerful new tool for generating transgenic animals for vertebrates and mammals, and a potential new vehicle for human gene therapy.Although piggyBac inserts itself randomly into the DNA, it most often locates in genes, making it useful for mutating genes and thus, revealing gene functions.

"This work represents another major step forward from Tian's laboratory. It teaches us how transposons work in mammalian systems, while providing a tool for the systematic study of gene function throughout the human and mouse genomes."

MEDICA.de; Source: Yale University