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Knockout mice at a The Merck Genome Research Institute (MGRI; West Point, PA, USA) has recently entered into an agreement with the biotechnology company Lexicon Genetics (Woodlands. TX. USA) to create 150 new ' knockout' mouse models. These will be distributed over a five-year period to the scientific community on a not-for-profit basi. The agreement mark the first large-scale u e of gene knockout technology to study the basic genetic mechanism of virtually any di ease proces .

Dr Arthur T. Sands, Pre ident and CEO of Lexicon Genetics. comments that their novel proprietary technology, gene trapping mutagenesi (Box 1), offers considerable advantages over gene targeting . . Using gene targeting, labs around the world can onl y make around 250 different knockout mice each year. In the same time frame, using our technology. we can create mutation for 50 000 genes.' The 150 knockout mice will be selected by a Mou e Mutation Selection Committee (Box 2) from Lexicon Genetic' OmniBank library. which is planned to eventually con ist of mou e clone containing 50 000 different mutation. cryopre erved as colonies of embryonic stem (ES) cell. U ing an automated procedure. Lexicon expects to produce 50 000 mutations in the first year, followed by ISO 000 in the econd year and 300 000 in the third year. The intention is to offer researchers the facility of scanning the library and pulling out ES cells with the mutation that they are interested in. They e timate that it will take 4-{j months to produce each knockout mouse and will cost S100 000-200 000 per mutant line. The first mice are expected to be avai lable to re earchers as early as spring 199 Researchers will be asked to pay a nominal fee to

knock-down price? Box 1. Gene trapping mutagenesis technology

Lexicon Genetics ' gene trapping mutagene is technology allows researchers to create genetic de­ficiencies in any gene and then tudy the resulting pathology. Thi contrasts with the more usual approach, where researchers take individuals with a disea e and work back through family tudies to identify the causative mutant allele. (1) The fir t tep is to ' randomly catter' mutation in mou e embryonic tem (ES) cell DNA, using retroviruses tbat have been engineered as a 'gene trap' so that they are mutagenic. (2) An antibiotic re i tance marker is included with the retrovirus and allows re earchers to elect for ES cells that have undergone mutations in their gene rather than in non-coding region. (3) Using PCR, the sites of in ertion can be amplified to determine the equence of the interrupted exon. (4) The resulting ES clones are then frozen and tored in the

OmniBank library. (5) To produce knockout mice, the ES cells with the de ired mutation are thawed and injected into a fertilized mou e embryo that has been allowed to develop to the bla to­cy t tage; this produce a chimeric embryo. (6) The embryo is then implanted into a recipient mouse uterus and develop ' to produce a chimeric mou e that can be used to breed knockout mice.

Box 2. The Merck Genome Research Institute

The Merck Genome Re earch Institute (MGRI) i a free-standing, not-for-profit organization that was fully launched in March 1997 by Merck & Co. Inc. Its aim i to facilitate the development of new technology for the linkage of human genetic trait and to resolve the biological function of disease gene . 'Although over 5000 human genetic disea e are recognized, only 10-20% arc open to traditional genetic inve tigation: ays Dr C. Thoma Ca key, MGRl's Pre. ident. He add that many familie affected by a genetic disease are too small to allow positional cloning for a candi­date gene a performed for Huntington's di ease and cystic fibrosis . They intend that the resulting technology will be available to the entire biological research community, including the pharmaceu­tical industry. MGRI ha appointed a Mou e Mutation Selection Committee; this i compo ed of

ix leading cell biologist with expertise in sy terns thought to be amenable to knockout trat­egies, such as cancer, the immune respon e, central nervous y tern function and human hered­itary disea e . They plan to meet for the first time in July/August 1997 to decide on the first 40-45 knockout candidates and will then meet twice a year to decide on the rest. The commit­tee want re earchers to tell them which knockout candidates should be included in the project. Suggestions hould be sent, with the ca e for inclu ion and a gene accession number (if avail­able). to Dr Finley Au tin, Administrative Director, The Merck Genome Research Institute, PO Box 4, WP 42-300, Sumneytown Pike, We t Point, PA 194 6, U A (e-mail

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defray breeding costs and hipping, and will be offered a range of option including buying individual mutant mice or breeding pair~.

and. believes that the technology offers a paradigm shift in the drug discovery proce . allowing animal models to be developed much more rapidly. 'It creates the possibilit} of making predictions about how

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different drugs work before you have even made the drug. Mouse models can be u~ed to provide the mutagenic equivalent of "total inhibition" by a particular drug,' he ay . They should allow researchers to explore putative targ~ts such as enzymes, ion chan neb and receptor to identify the most effective one to create the phy~iological respon. e they want out of a drug.

Janet Fricker

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