Shortcut to manipulating specific genes in the mammalian genome

A research team around Wolfgang Wurst, Professor for Developmental Genetics at the Technische Universitaet Muenchen, has succeeded in manipulating selected genes in mouse zygotes in a single step. Using zinc-finger nucleases, they generated mutations without taking a detour via mouse embryonic stem cells. Over the long term, these findings concerning targeted gene manipulation will save valuable research time and will be universally applicable to other mammalian cells to investigate gene functions. The results of this study have now been published in the online early edition of the Proceedings of the National Academy of Sciences (PNAS).

Until now, researchers have primarily relied on the mouse model system in order to understand mammalian genes and their functions. For this purpose, they generate mutations in mouse embryonic stem cells. These mutations are subsequently transferred into the next generation via mouse chimeras. Professor Wolfgang Wurst and his research team at Helmholtz Zentrum München have now found a shortcut. Using zinc-finger nucleases and selected gene fragments, they have succeeded in generating specific, designed mutations directly in mouse zygotes. The advantages of this method: savings in time, higher efficiency and most of all, applicability to other mammalian cells, which will have great potential in the future.

The tools used in this novel method are artificially designed zinc-finger nucleases (ZFNs), synthetic proteins which are able to cleave DNA at a specifically determined site. Together with a gene targeting vector that contains the mutations under investigation, the ZFNs are injected directly into the murine one-cell embryos. The endogenous repair system induces the desired gene fragment into the mouse DNA with an achievement rate of 1.7 to 4.5 percent without prior selection. Using this method, the researchers have succeeded in breeding vital mice in which targeted specific genes have been replaced.

Now the researchers are seeking to improve the effectiveness of the method and are investigating the applicability of the method to other organisms. Scientists could thus use other model systems besides the mouse model. The new method also offers promising therapeutic approaches. "In the long run," Professor Wurst sais, "it is conceivable that not only new genes can be inserted using this method, but also that defective genes can be replaced with healthy ones."

This work was financially supported by the European Union within the European Conditional Mouse Mutagenesis Program and by the German Ministry of Education and Research within the DIGTOP project of the NGFN-Plus program.

Publication:
Melanie Meyer, Martin Hrabe de Angelis, Wolfgang Wurst und Ralf Kuhn: Gene targeting by homologous recombination in mouse zygotes mediated by zinc-finger nucleases. Proceedings of the National Academy of Sciences; Early Edition, 04.08.2010 – DOI: 10.1073/pnas.1009424107

Source: Technical University