Production of Transgenic Mice Transgenic animals are produced by injecting a DNA construct directly into the pronucleus of a newly fertilized mouse egg. In some eggs, the DNA will integrate into the mouse chromosomal DNA before cell division, and will be present in all cells in the mouse including the germ line. The Transgenic Animal Production service consists of injecting each construct into 300-350 eggs. Twenty to fifty mice will normally be born from this number of injected eggs. These animals are then screened for the presence of the transgene. The number of transgenic animals typically varies from two to eight, and these animals are transferred to the investigator at weaning. Weaning is performed at 21 days of age, so transgenic founders are received six weeks after the original egg injections are performed. For all constructs, the investigator must provide the transgenic construct prepared by a suitable protocol as well as primers for a sensitive polymerase chain reaction genotyping assay.
Production of Chimeric Mice
Injecting embryonic stem cells into the cavity of a mouse blastocyst produces chimeric mice. Chimeric mice resulting from injected blastocysts will be composed of tissue derived from the inner cell mass of the host blastocyst as well as the embryonic stem cells. It is possible for embryonic stem cells to contribute to all cells of the chimeric mouse, including the germ cells. Typically, chimeric mice are used to produce animals derived entirely from embryonic stem cells that have been manipulated in culture to contain a targeted mutation. Most commonly, chimeric mice are produced from embryonic stem cells derived from agouti 129/SV mice and host blastocysts harvested from black C57Bl/6 mice. The chimeric mouse production service consists of injecting embryonic stem cells provided by the investigator into 150-175 blastocysts, representing three days of work. Twenty to forty live mice are normally born from this number of injected blastocysts. Typically two to six mice will have skin with greater than seventy percent area of agouti coloring, indicating a good chance for embryonic stem cell contribution to the germline. These animals are transferred to the investigator at weaning. Weaning is performed at 21 days of age, so chimeric animals are received six weeks after the original blastocyst injections are performed. For all constructs, the investigator must provide embryonic stem cells proven to be pathogen free.
Single Day Injection Service
Additional injections may be paid for on a daily basis after one round of the standard service has been performed if needed to generate additional positive offspring.
Animal Husbandry
The husbandry service includes all aspects of maintaining mice, including inbred mice and mice containing induced mutations: breeding and weaning, tail biopsies, polymerase chain reaction genotyping, computer database colony tracking, and mouse monitoring. In addition, the Washington University Mouse Genetics Core offers ancillary services to husbandry, including injections, urine and blood collection, and dissections. Each experimental colony or group is independently tracked, and a weekly report of inventory and procedures is provided.
Genotyping by Tail PCR
Genotyping will be performed using a polymerase chain reaction assay and includes screening for induced mutations such as transgenes and "knockouts." Tissue for genotyping is derived from tail biopsies taken at 5-7 days of age, and assay results are normally obtained by two weeks of age.
Rederivations
The rederivation service takes mice that have been exposed to a specific pathogen and produces mice that are free of disease. Embryos derived from infected mice are transferred into recipient females free from specific pathogens, and these recipients are transferred to quarantine after implantation surgery.
Cryopreservation
Cryopreservation of mouse embryos is offered to "store" lines of animals not currently needed, to reduce cage costs and cage space, or to provide secure stock in case of contamination. The success of cryopreservation is strain dependent. Thus, feasibility and cost may vary for a particular strain.
Ovarian Transplants
Ovarian transplants are offered to maintain lines with normal ovaries but a phenotype that precludes breeding.
In Vitro Fertilization
In vitro fertilization is offered to aid in propagating mice that are poor breeders or have become too old to breed naturally. The price includes isolation and use of sperm from 2 males or eggs from up to 4 females. The success of in vitro fertilization is strain dependent. Thus, feasibility and cost may vary for a particular strain.
Vasectomies
Vasectomies are performed on any strain, and males are available for mating ten to twelve days after surgery.
