About the Facility

The Transgenic Mouse System

Integration and modification of genes into the mouse genome serve to establish experimental systems that are critical to study normal as well as altered gene expression. Such studies can serve to identify genes essential for normal development and generate animal models for the study of human diseases.

Direct microinjection of DNA into the male pronucleus of a mouse zygote has been the method most extensively used in the production of transgenic mice. If the foreign DNA integrates into the mouse chromosomal DNA at the one-cell stage, the transgenic animal will contain the injected DNA in every cell, including those of the germ line. If, however, integration occurs later, the resulting animals will be mosaic for the presence of the injected DNA. The number of copies of integrated DNA can vary from one to several hundred, arranged primarily in tandem head to tail arrays.

The production of chimeric mice by introducing Embryonic Stem (ES) cells into early embryos is an alternative approach to generating transgenic mice. This technique utilizes the ES tissue culture system to modify and select ES cells that have received an exogenous DNA of interest. Once derived and characterized, ES cell clones may be transferred into 4-day-old mouse embryos (blastocysts) where they can differentiate into any adult tissue type. The choice of mouse strain is of great importance: donor embryos that would generate ES cells and host embryos that would receive transferred cells are obtained from different strains of mice carrying different eye or coat pigmentation. This facilitates the visual distinction between cell populations in the adult “chimeric mouse”.

More recent technologic advances now allow for the direct introduction of mutations into the mouse genome via directed endonucleases (TALEN and CRISPR/Cas9). This technology has further increased the power and flexibility of modified mouse model generation. These direct genome editing methodologies eliminate the need for ES cell manipulations and have the capacity to generate mouse models in a time frame that significantly outpaces prior approaches with a consequent major acceleration in the timing of critical studies and a commensurate decrease in cost.

The Facility

The purpose of the Transgenic & Chimeric Mouse Facility is to provide a centralized service to efficiently produce genetically altered mice for basic research. This should result in reduction in effort and cost to participating investigators. The facility is located on the basement level of the Clinical Research Building. This facility consists of an animal room and several injection rooms. The injection rooms are fully equipped to carry out the entire procedure of making transgenic mice. The animal room provides housing and breeding space for the mice involved in the transgenic projects. The facility uses sterile food and water as well as autoclaved cages and bedding; all cages are of the microisolator type to limit the spread of colony infection. The entire facility is located behind a microbiologic barrier where admittance is strictly limited.

Contact Information


38-40 Clinical Research Building

Mailing Address:

500 Clinical Research Building
415 Curie Boulevard
Philadelphia, PA 19104-6145
Telephone: 215-573-3023
Fax: 215-573-5892