Commonly Asked Questions


What does the Transgenic Core do?
The Transgenic Core routinely prepares genetically modified mice and rats for University of Michigan investigators (transgenic mice, transgenic rats, knockout mice, and knockout rats). These animals can be used to study gene function, gene expression, gene regulation, to develop animal models of human disease, to test gene therapy reagents, to establish cell lines from specific cell types transformed in vivo, to produce mice with tissue-specific inducible gene expression or tissue-specific gene deletions, or to study the effects of cell specific ablation with toxigenes.

We provide access to our micromanipoulation and embryos stem cell workstations along with necessary reagents:

  • specialized plasmids
  • embryonic stem (ES) cell lines
  • FBS
  • feeder cells certified for ES cell culture.

  • The Transgenic Core provides assisted reporductive technology for mice and rats including
    The Transgenic Core derives specific pathogen free mice or rats  from pathogen infected animals.
    Hands-on training is proved to individuals in all aspects of transgenic technology.

    Refer to the list of services or read the detailed service description.

    How do I submit a transgene?
    Visit the submission page for instructions.

    How much does it cost?
    University of Michigan investigators review the fee schedule.
    Members of the following University of Michigan centers receive discounts:

    Service Request Forms are available by download.

    When will my service request be processed?
    The Transgenic Core prioritizes all requests for service on a "first-come, first-serve" basis. This standard is applied to everyone equally, even our faculty directors. The time between transgene DNA submission and microinjection is updated regularly. Typically ES cell work is scheduled one to three months ahead. Since the inception of the Transgenic Core our policy has been that no project, whether it be gene targeting in ES cells or a transgenic mouse model, will enter the work queue until all of the required materials are provided. This includes both scientific materials, such as DNA samples and genotyping tests, and paperwork, such as approval to use animals in research,  material transfer agreements and billing information.

    How effective is the Transgenic Core?
    Both transgenic and gene targeting efficiencies are excellent. We guarantee that at least three transgenic founders will be produced (the average number is 10). Since 1989 over 7000 transgenic founders were produced from over 700 transgene constructs as of September 2003. These efficiency of transgenic production equals or exceeds values in the published transgenic mouse  literature. The efficiency of all steps in gene targeting compare favorably with literature values. Multiple embryonic stem (ES) cell lines have been imported and screened for germline chimera formation. In addition, we have developed our own 129X1/SvJ ES cell line "Pat5".  See the list of ES cell lines. We have collaborated with investigators to generate 70 new strains of mice (as of September 2003) from ES cells with mutations introduced by recombination with targeting vectors.

    What about consultation?
    We provide advice on all aspects of this technology from experimental design to mouse breeding. We can provide protocols and training for every step in the process of generating transgenic or gene targeted mice. We are ready to interact, our doors are open, please contact us with any questions Meet the Staff.

    What kind of paperwork is involved?
    Any project that uses mice must be approved by the University Committee on Use and Care of Animals. Concat the UCUCA for innformation on how to apply for permision to use vertebrate animals in research testing or instruction. The Unit for Laboratory Animal Medicine provides animal housing and veterinary care. Investigators approved for animal research are expected to provide ULAM with a shortcode that can be used to pay for veterinary care and housing costs. Transgenic Core submission forms require the following information: 

  • UCUCA approval number
  • ULAM shortcode number for animal housing and veterinary care

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    Please note that the information on transgenic mice below applies equally to transgenic rats.
    What is a transgenic mouse/rat?
    A transgenic mouse or rat has a transgene in addition to its normal complement of genes. A transgene is an artificial gene cloned in the lab by recombinant DNA technology and microinjected into fertilized mouse or rat eggs. Eggs are transferred into foster mothers for gestation. Transgenic progeny are bred to produce a line. Transgenes integrate randomly into chromosomal DNA and are transmitted as a Mendelian trait.

    What is involved in making transgenic mice/rats?
    The Core is available for consultation on all phases of transgenic research. The investigator designs and clones the transgene and develops a genotyping assay with single gene copy sensitivity, usually PCR based. A genotyping assay that detects an endogenous single copy gene in the mouse or an endogenous gene in the rat is a necessary positive control. The assays for the transgene and the endogenous gene are used to test all potential transgenic founder mice or rats. The combination of assays eliminates both false negatives and false positive mis-identifications. Transgene DNA is purified by the Transgenic Core for microinjection from a restriction digest supplied by the investigator. The Core microinjects DNA into fertilized (C57BL/6 X SJL)F2 eggs and transfers the eggs into pseudopregnant mice. Alternatively, we will make transgenic mice in other genetic backgrounds, upon request. We have successfully made transgenic mice in C57BL/6 X SJL)F2, FVB/N, C57BL/6,  (C57BL/6 X DBA/2)F2, SWR, B10D2 congenic strains, and mutant strains such as mnd2, Myo15sh2,  and C57BL/10ScSn-Dmdmdx/J. When the pups are 2 weeks old, the Core applies ear tags and obtains tail biopsies from the mice. The Core will provide the tail biopsies to the investigator. Investigators may prepare genomic DNA from tail biopsies by hand or by any of the numerous kits on the market (see Protocols). The investigator will identify the transgenic mice by PCR. The transgenic mice are transferred to the investigator for breeding and analysis of transgene expression.

    What can I do to maximize a successful transgenic outcome?
    We guarantee that you will receive 3 or more transgenic mice or rats, however we can not guarantee transgene expression or transmission. The best strategy is to use a promoter that is already well characterize in transgenic mice or to employ very large flanking regions greater than 10 Kb. Alternatively, a bacterial artificial chromosome can be used to direct gene expression. BACs are include over 100Kb of genomic DNA sequence and often direct gene expression in a fashion which close matches the expression of endogenous genes.

    The yield of transgenics is optimized by injecting highly purified linear DNA fragments with overhanging ends. Remove as much vector sequence as possible from the construct since prokaryotic sequences inhibit transgene expression. Although not a guarantee, demonstrated expression in a cell line is a positive indicator of in vivo expression and provides a rapid, inexpensive method to demonstrate that the transgene has been constructed properly. Contact Thom Saunders for more information on transgene design.

    How many transgenic mice/rats will I get?
    We guarantee that you will receive a minimum of three transgenic founders, often more. The purity of the microinjection DNA is the single most important factor which determines how many transgenic founders will be produced.  Another very important parameter is the reliability and sensitivity of the screen for the transgene.

    What if my DNA construct is lethal?
    If you believe that your construct may be lethal, we will co-inject a neutral DNA fragment as a marker. If your transgene is not lethal then mice with both the transgene and neutral marker will be detected. However, if only mice with the neutral marker are detected then the construct is likely to be embryonic lethal. Alternatively you choose to examine transgenic founders. Transgenic embryos can be analyzed at various developmental ages to determine the time of death during gestation.

    What is the significant of transgene copy number?
    For the majority of transgenes the copy number does not correlate with expression level. The exceptions occur when large genomic fragments are used to make transgenics. Examples include P1 clones (90 Kb), BACs (180 Kb,) or YACs (400 Kb). Some reports suggest that if you use locus control regions or matrix attachment regions around your transgene that you may be able to insulate if form integration effects. Previous work in the literature has shown that attempts to produce low copy numbers by microinjecting dilute DNA does not affect copy number, but does reduce the overall yield of transgenic mice.

    What if my transgene is too big?
    The size of your transgene should not interfere with transgenic mouse production. Large transgenes may be difficult to clone. You may wish to consider BAC recombineering to produce large transgenes under the control of regulatory elements in the BAC. The Core has produced transgenics from Bacterial Artificial Chromosomes up to 180 Kb in size. There are reports in the literature of transgenic mice produced from the microinjection of 90 Kb P1 clones, 248 Kb yeast artificial chromosomes, and even microdissected chromosome fragments.


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    What is a gene targeted mouse?
    Gene targeted mice are derived from  embryonic stem (ES) cells. ES cells are manipulated in culture by introducing a targeting vector that is cloned in the lab by recombinant DNA technology. The targeting vector DNA precisely replaces a segment of chromosomal DNA (hence the name "gene targeting") in the ES cell. ES cells are injected into a normal mouse blastocyst where they mingle with the embryo' s cells to form the developing mouse. Up to 100% of the resulting mouse chimera can be formed from cells descended from the ES cells. ES cell-derived-mouse chimeras are bred to normal mice to produce progeny carrying the targeted gene which is transmitted as a Mendelian trait.

    What is involved making gene targeted mice?
    The major stumbling block in this process is the identification of ES cell clones that have undergone homologous recombination between the targeting vector and the chromosome in the ES cell. To maximize a successful outcome: 1) make sure that the genomic DNA in  your targeting vector is isogenic with the ES cell line question and 2) develop a hybridization screen that will detect your wild type gene in 2 ug of genomic ES cell DNA. We encourage you to contact Thom Saunders for a consult on your targeting vector design and on all phases of gene targeting research. The first step in the process is to obtain and map and sequence a 129X1/Sv genomic clone of the gene of interest. A 129X1/Sv library is available for screening from the core. The investigator designs and clones the targeting vector and purifies it for electroporation into embryonic stem (ES) cells. The Core has numerous plasmids designed for targeting vector construction. The targeting vector is then electroporated into ES cells by Core personnel, clones are picked after drug selection, the clones are cryopreserved at -80 C while the investigator screens DNA from the clones to identify those which have undergone homologous recombination. Alternatively, the Core will train you in ES cell culture and provide you with quality tested reagents and space in the multi-user Mouse Embryonic Stem Cell Laboratory so that you can do the work yourself. After the investigator isolates euploid ES clones which have undergone homologous recombination with the targeting vector they are microinjected into mouse blastocysts and transferred into pseudopregnant recipients. When the resulting pups are three weeks old, they are scored for ES cell contribution and transferred to the investigator for breeding and analysis.

    What can I do to maximize a successful gene targeting outcome?

    We can guarantee that we will inject your embryonic stem (ES) cells into a minimum of 50 blastocysts for ES cell-mouse chimera formation. Because of the intrinsic variability in individual ES cell clones, we can not guarantee that chimeras will be produced or that they will transmit your targeted gene through the germline. Therefore, we recommend that you provide at least three clones for microinjection. In collaboration with other labs on campus, we have successfully targeted over 60 genetic loci. We are confident in that we can work with you to genetically engineer new strains of mice that carry novel mutations of value to your research. The Core provides plasmids for gene targeting, ES cell lines that have been tested for germline chimera formation, feeder cells for ES cell culture, FBS tested for ES cell culture, and training in the exacting techniques required for successful ES cell culture. Contact Thom Saunders for more information on gene targeting projects.

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    NIH IRP Guidelines for the Availability of Transgenic/Knockout Animals

    Transgenic and gene "knockout" animals that have been developed using NIH IRP (intramural research program) funds and resources will be provided to other laboratories following publication of descriptions of the animals in the peer reviewed literature. It is an obligation of NIH intramural scientists to make such animals widely available for research purposes. This can be achieved by making arrangements to send breeding pairs to a central repository such as the Induced Mutant Resource at the Jackson Laboratory. This would assure the availability of clean, genetically characterized animals within a year's time. An attempt should be made to reduce duplication of effort by setting up collaborative experiments whenever possible; however, this should not be used as a mechanism to inhibit the distribution of animals.

    These guidelines for the IRP are now in agreement with those of the US Public Health Service (PHS) for the extramural community: "It is the policy of PHS to make available to the public the results and accomplishments of the activities that it funds...Therefore, when these resources are developed with PHS funds and the associated research findings have been published or after they have been provided to the agencies under contract, it is important that they be made readily available for research purposes to qualified individuals within the scientific community. This policy applies to grants, cooperative agreements, and contracts."

    These guidelines supplement those already covered by the NIH Guide for other types of biological materials and resources. The NIH Guide is available online.


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    Review Articles

    Auerbach AB, Norinsky R, Ho W, Losos K, Guo Q, Chatterjee S, Joyner AL. 2003. Strain-dependent differences in the efficiency of transgenic mouse production. Transgenic Res. 12:59-69.

    Adams DJ, van der Weyden L.Contemporary approaches for modifying the mouse genome. 2008. Physiol Genomics. 34::225-38.

    Brinster RL, Chen HY, Trumbauer ME, Yagle MK, Palmiter RD. 1985. Factors affecting the efficiency of introduction foreign DNA into mice by microinjecting eggs. Proc. Natl. Acad. Sci. (USA) 82:4438-4442.

    Brinster RL, Allen JM, Behringer RR, Gelinas RE, Palmiter RD. 1988. Introns increase transcriptional efficiency in transgenic mice. Proc Natl Acad Sci U S A. 85:836-40.

    Camper SA. 1987. Research applications of transgenic mice. Biotechniques 5, 638-650.

    Capecchi MR. 1994. Targeted Gene Replacement. Sci. Am. March 1994. pp. 52-59.

    Filipiak WE, Saunders TL. Advances in transgenic rat production. Transgenic Res. 2006 Dec;15(6):673-86.

    Galli-Taliadoros LA, Sedgwick JD, Wood SA, Korner H. 1995. Gene Knock-out Technology: A Methodological Overview for the Interesetd Novice. J. Immunol. Meth. 181:1-15.

    Hammer RE, Krumlauf R, Camper SA, Brinster RL, Tilghman SM. 1987.  Diversity of alpha-fetoprotein gene expression in mice is generated by a combination of separate enhancer elements. Science. 235:53-8.

    Hughes ED, Qu YY, Genik SJ, Lyons RH, Pacheco CD, Lieberman AP, Samuelson LC, Nasonkin IO, Camper SA, Van Keuren ML, Saunders TL.2007. Genetic variation in C57BL/6 ES cell lines and genetic instability in the Bruce4 C57BL/6 ES cell line. Mamm Genome. 18:549-558.

    Muller, U. Ten years of gene targeting: targeted mouse mutants, from vector design to phenotype analysis. 1993. Mechanisms of Development 82:3-21.

    Palmiter RD, Sandgren EP, Avarbock MR, Allen DD, Brinster RL. 1991. Heterologous introns can enhance expression of transgenes in mice. Proc Natl Acad Sci U S A. 88:478-82.

    Pettitt SJ, Liang Q, Rairdan XY, Moran JL, Prosser HM, Beier DR, Lloyd KC, Bradley A, Skarnes WC. 2009. Agouti C57BL/6N embryonic stem cells for mouse genetic resources. Nat Methods. 6:493-465.

    Schneider MR, Wolf E. 2005. Genotyping of transgenic mice: old principles and recent developments. Anal Biochem. 344:1-7.

    Saunders TL. 2003. Reporter molecules in genetically engineered mice.Methods Mol Biol. 209:125-143.

    Skarnes WC, Rosen B, West AP, Koutsourakis M, Bushell W, Iyer V, Mujica AO, Thomas M, Harrow J, Cox T, Jackson D, Severin J, Biggs P, Fu J, Nefedov M, de Jong PJ, Stewart AF, Bradley A. 2011. A conditional knockout resource for the genome-wide study of mouse gene function. Nature.474:337-342.


    Townes TM, Lingrel JB, Chen HY, Brinster RL, Palmiter RD. 1985. Erythroid-specific expression of human beta-globin genes in transgenic mice. EMBO J. 4:1715-23.

    Van Keuren ML, Saunders TL. 2004. Rederivation of transgenic and gene-targeted mice by embryo transfer. Transgenic Res. 13:363-71.

    Van Keuren ML, Gavrilina GB, Filipiak WE, Zeidler MG, Saunders TL. 2009. Generating transgenic mice from bacterial artificial chromosomes: transgenesis efficiency, integration and expression outcomes. Transgenic Res. 18:769-785.

    Wilkie TM, Brinster RL, Palmiter RD. 1986. Germline and somatic mosaicism in transgenic mice. Dev Biol. 118:9-18.

    Gene Targeting : A Practical Approach Joyner  AL, ed. 2000. IRL Press at Oxford University Press. New York. Oxford University Press; ISBN: 019963792X.

    Books  MIRLYN: The University of Michigan Online Public Access Catalog

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