Genetically Modified Mouse Core (GMMC)

Transgenic and Chimeric Mouse Facility

The Transgenic and Chimeric Mouse Facility provides a centralized service to efficiently produce infection-free transgenic, chimeric, and genome-edited strains of mice. These mice carry randomly inserted transgenes and/or site-specific alterations in the mouse genome of specific interest to Penn researchers. The Facility offers services including DNA pronuclear injection into fertilized oocytes (along with genotyping of transgenic founders), ES cell injection into blastocysts, cytoplasmic/pronuclear injections into fertilized oocytes of CRISPR-Cas9 mix (gRNA, Cas9RNA, ssDNA/dsDNA templates), embryo and sperm cryopreservation, in vitro fertilization, and re-derivation of live and cryopreserved lines. The Core also oversees a cyropreservation facility for long-term storage of mouse embryos and sperm samples.

Grant Citation

Please cite the Center for Molecular Studies in Digestive and Liver Diseases (P30DK050306) in all publications related to core usage.


Douglas J. Epstein, Ph.D. -

Core Personnel

Technical Director

Jean Richa, Ph.D. -


  • DNA Injection

    Injection of DNA into mouse zygotes (fertilized oocytes) for the production of transgenic mice or embryos.

  • ES cell Injection

    Injection of embryonic stem cells into blastocysts (3.5-day embryo) for the production of chimeric mice.

  • RNA Injection

    Injection of a mix of Cas9 RNA/prot., gRNA and/or ssDNA/dsDNA into mouse zygotes for the production of site-directed genome-edited mice.

  • Mouse Line Rederivation

    Surgical transfer of embryos into pathogen-free recipient females, where they can develop to term.

  • Embryo Cryopreservation

    Controlled freezing of mouse embryos for preservation in liquid nitrogen.

  • Sperm Cryopreservation

    An alternate and less expensive procedure to preserve important mouse lines.

  • In-Vitro Fertilization

Through this process, a mouse line that undergoes reproductive obstacles can be rescued.