REVIEWA Review of Current Large-Scale Mouse Knockout EffortsChunmei Guan, Chao Ye, Xiaomei Yang,* and Jiangang Gao*College of Life Science, Shandong University, Jinan 250100, Shandong, People’s Republic of ChinaReceived 27 August 2009; Revised 25 October 2009; Accepted 13 November 2009Summary: After the successful completion of the humangenome project (HGP), biological research in the post-genome era urgently needs an efficient approach forfunctional analysis of genes. Utilization of knockoutmouse models has been powerful for elucidating thefunction of genes as well as finding new therapeuticinterventions for human diseases. Gene trapping andgene targeting are two independent techniques for mak-ing knockout mice from embryonic stem (ES) cells. Genetrapping is high-throughput, random, and sequence-tagged while gene targeting enables the knockout ofspecific genes. It has been about 20 years since the firstgene targeting and gene trapping mice were generated.In recent years, new tools have emerged for both genetargeting and gene trapping, and organizations havebeen formed to knock out genes in the mouse genomeusing either of the two methods. The knockout mouseproject (KOMP) and the international gene trap consor-tium (IGTC) were initiated to create convenient resour-ces for scientific research worldwide and knock out allthe mouse genes. Organizers of KOMP regard it as im-portant as the HGP. Gene targeting methods havechanged from conventional gene targeting to high-throughput conditional gene targeting. The combinedadvantages of trapping and targeting elements areimproving the gene trapping spectrum and gene target-ing efficiency. As a newly-developed insertional muta-tion system, transposons have some advantages overretrovirus in trapping genes. Emergence of theinternational knockout mouse consortium (IKMP) is thebeginning of a global collaboration to systematicallyknock out all the genes in the mouse genome forfunctional genomic research. genesis 48:73–85, 2010.V C 2010 Wiley-Liss, Inc.Key words: knockout mouse; gene trapping; genetargeting; transposon; ES cellsINTRODUCTIONThe past century has witnessed a boom in moleculargenetics and one of the greatest projects—the human ge-nome project (HGP) (Abramowicz, 2003; Johnson,1987; Watson and Cook-Deegan, 1991). Accomplish-ment of this project provides us with the sequence infor-mation of our genome, which is now available to diag-nose diseases at the level of genes (Burton and Stewart,2003; Collins and Mansoura, 2001; Gottesman andCollins, 1994). Biological research has entered a newstage—the post-genome era, and the main work of thisera is to decipher the function of each gene in our ge-nome (Austin et al., 2004; Eisenberg et al., 2000). Com-parative genomics has shown that the mouse and humangenomes have high homology (Gregory et al., 2002).Therefore, the mouse serves as a perfect model animalfor functional genomic research of humans. The most ef-ficient way to study the function of a gene is to make aknockout and observe the phenotype in the whole ani-mal (Austin et al., 2004; Brown and Hancock, 2006;Dinnyes and Szmolenszky, 2005). Knockout mice canalso be used for mouse models of human diseases.There are two main methods to make knockout mice:gene targeting and gene trapping. Gene targeting tech-nology is based on successful ES cell culture and in vitrohomologous recombination, and it is a good method forgene knockout and knock-in to introduce loss-of-func-tion mutations in the mouse genome (Hogan and Lyons,1988). The first mouse gene targeting experiment wascompleted in 1987 (Mansour et al., 1988; Thomas andCapecchi, 1987). Gene targeting has accelerated thestudy of gene function during the last 20 years and gen-erated crucial resources for biological research. In 2007three scientists were awarded the Nobel Price for theirresearch on the important technology of gene targeting(Mak, 2007).Gene trapping mutagenesis was developed as an alter-native to gene targeting technology. It is a high-through-put and random mutation technique (Abuin et al., 2007;Gossler et al., 1989; Kothary et al., 1988). Though not asspecific as gene targeting, a large number of mouse genescan be knocked out in a short period of time by trapping(Takeuchi, 1997; Zambrowicz and Friedrich, 1998).The combination of gene trapping and gene targetingmakes it possible to knock out all the mouse genes.Chunmei Guan and Chao Ye contributed equally to this work.*Correspondence to: Xiaomei Yang and Jiangang Gao, College of Life Sci-ence, Shandong University, South Building, Room 117, Jinan 250100, Shan-dong, People’s Republic of China.E-mail: jggao@sdu.edu.cn and yxm411@sdu.edu.cnPublished online 21 January 2010 inWiley InterScience (www.interscience.wiley.com).DOI: 10.1002/dvg.20594' 2010 Wiley-Liss, Inc. genesis 48:73–85 (2010)
