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Novel development in mouse phenotyping 2014: et al., The International Knockout Mouse Consortium (IKMC) developed high throughput gene trapping and gene targeting pipelines that produced mostly conditional mutations of more than 18,500 genes in C57BL/6N mouse embryonic stem (ES) cells which have been archived and are freely available to the research community as a frozen resource. From this unprecedented resource more than 6000 mutant mouse strains have been generated by the IKMC in collaboration with the International Mouse Phenotyping Consortium (IMPC). In addition, a cre-driver resource was established including 250 C57BL/6 cre-inducible mouse strains. Complementing the cre-driver resource, a collection comprising 27 rAAVs expressing cre in a tissue-specific manner has also been produced. All resources are easily accessible from the IKMC/IMPC web portal (www.mousephenotype.org). The IKMC/IMPC resource is a standardized reference library of mouse models with defined genetic backgrounds enabling the analysis of gene-disease associations in mice of different genetic makeup and should therefore have a major impact on biomedical research., The authors are supported by the EUCOMMTOOLS project which is funded by the European Commission [FP7-HEALTH-F4-2010-261492] and UM1-HG006370-06 (TFM, JW); the National Insitute of Health U54 HG006370 (TFM, DS and SDMB), U42 OD011185 (SAM), HG006364-03S1 (KCKL), and U42 OD011175 (CM and KCKL); NorCommTLS (MRI, Government of Ontario) and Genome Canada (OG-090) (LMJN, CM); the Manitoba Research Innovation Fund (GGH); Genome British Columbia AGCP-CanEuCre-01 award (EMS). National Centre for Scientific Research (CNRS), the French National Institute of Health and Medical Research (INSERM), the University of Strasbourg (UDS), the “Centre Européen de Recherche en Biologie et en Médecine” the French state funds through the “Agence Nationale de la Recherche”, Investissements d’Avenir labelled ANR-10-IDEX-0002-02, ANR-10-LABX-0030-INRT, ANR-10-INBS-07 PHENOMIN to YH.

The gene FUS (also known as TLS (for translocated in liposarcoma) and hnRNP P2) is translocated with the gene encoding the transcription factor ERG-1 in human myeloid leukaemias. Although the functions of wild-type FUS are unknown, the protein contains an RNA-recognition motif and is a component of nuclear riboprotein complexes. FUS resembles a transcription factor in that it binds DNA, contributes a transcriptional activation domain to the FUS-ERG oncoprotein and interacts with several transcription factors in vitro. To better understand FUS function in vivo, we examined the consequences of disrupting Fus in mice. Our results indicate that Fus is essential for viability of neonatal animals, influences lymphocyte development in a non-cell-intrinsic manner, has an intrinsic role in the proliferative responses of B cells to specific mitogenic stimuli and is required for the maintenance of genomic stability. The involvement of a nuclear riboprotein in these processes in vivo indicates that Fus is important in genome maintenance.

Distal lung development occurs through coordinated induction of myofibroblasts, epithelial cells, and capillaries. Lunatic Fringe ( Lfng) is a β1–3N-acetylglucosamine transferase that modifies Notch receptors to facilitate their activation by Delta-like (Dll1/4) ligands. Lfng is expressed in the distal lung during saccular development, and deletion of this gene impairs myofibroblast differentiation and alveogenesis in this context. A similar defect was observed in Notch2β-geo/+Notch3β-geo/β-geocompound mutant mice but not in Notch2β-geo/+or Notch3β-geo/β-geosingle mutants. Finally, to directly test for the role of Notch signaling in myofibroblast differentiation in vivo, we used ROSA26-rtTA/+; tetO-CRE/+; RBPJκflox/floxinducible mutant mice to show that disruption of canonical Notch signaling during late embryonic development prevents induction of smooth muscle actin in mesenchymal cells of the distal lung. In sum, these results demonstrate that Lfng functions to enhance Notch signaling in myofibroblast precursor cells and thereby to coordinate differentiation and mobilization of myofibroblasts required for alveolar septation.

Mouse knockout technology provides a powerful means of elucidating gene function in vivo, and a publicly available genome-wide collection of mouse knockouts would be significantly enabling for biomedical discovery. To date, published knockouts exist for only about 10% of mouse genes. Furthermore, many of these are limited in utility because they have not been made or phenotyped in standardized ways, and many are not freely available to researchers. It is time to harness new technologies and efficiencies of production to mount a high-throughput international effort to produce and phenotype knockouts for all mouse genes, and place these resources into the public domain.

To the editor: Gene trapping is a high-throughput approach that can be used to introduce insertional mutations across the genome in mouse embryonic stem (ES) cells. Gene trap vectors simultaneously mutate and report the expression of the endogenous gene at the site of insertion and provide a DNA tag for the rapid identification of the disrupted gene. The generation of mutant mice from a large collection of ES cell lines carrying gene trap insertions could be applied to large-scale functional analysis of the ~30,000 mammalian genes. The overall impact of gene trap resources will rest on the fraction of the genome that is accessible with this technology, the efficiency relative to other competing technologies and the availability of such a resource to the academic community. Lexicon Genetics, a US-based biotechnology company, was the first to implement a genome-wide gene trapping program1 and has developed OmniBank (http://www.lexicon-genetics.com), the largest library of mutant ES cell lines. A parallel effort was initiated in the public domain by several academic groups in the International Gene Trap Consortium (IGTC; http://www.igtc.ca). The recent release of OmniBank sequence tags to GenBank2 has made it possible to compare the size and efficiency of the existing gene trap libraries. We confirm that Lexicon achieved close to 60% coverage of the genome from 200,000 OmniBank sequence tags deposited in GenBank (Fig. 1). Our analysis, supported independently by Lexicon3, indicates that the rate of trapping new genes was not linear but declined within the first 100,000 tags to a rate at which 1 new gene was added every 35 tags, comparable to the efficiency of high-throughput gene targeting methods4. To date, the IGTC has attained 32% genome coverage in 27,000 tags; trapping is likewise nonlinear, but the initial rate seems to be somewhat faster than Lexicon’s (Fig. 1). The seemingly higher efficiency may relate to the diversity of plasmid and retroviral vector designs used by the IGTC that could help overcome insertion site preferences of any single vector5; further studies are needed to fully understand how vector design and other experimental factors influence the efficiency of gene trapping. One-fifth of the genes trapped by the IGTC were not represented in the sequence tags released by Lexicon (Supplementary Tables 1-3 online). Thus, the two efforts together have trapped nearly two-thirds of all genes in mice. We conclude that gene trapping is an effective strategy to mutate a substantial fraction of the genes in mice that compares favorably with gene-targeting approaches. Furthermore, we continue to refine the technology, particularly in developing strategies for postinsertional modification of the trapped loci to create a wide range of desired alleles. The IGTC will provide an important public resource of new mutations in mice that will accelerate the pace of functional annotation of the mammalian genome. Figure 1 Comparison of the rates of trapping of the IGTC and OmniBank resources. Unique Ensembl genes were identified using MAPTAG (http://www.sanger.ac.uk/Software/MAPTAG), an automated annotation program that identifies short, almost perfect matches to gene ... Gene trap cell lines generated by the IGTC are available without restriction (http://baygenomics.ucsf.edu; http://www.genetrap.de; http://www.escells.ca; http://www.sanger.ac.uk/genetrap; http://www.fhcrc.org/labs/soriano/GTdb; http://www.cmhd.ca) and all sequence tags are mapped on the Ensembl mouse genome browser http://www.ensembl.org/Mus_musculus/; select DAS Source ‘GeneTrap’).