*Dear MMRRC Users: We are actively monitoring the situation with COVID-19. While currently we are still operational, the situation could change with short notice. Should events and recommendations warrant, several aspects of our program will be impacted. While we will do everything possible to prevent disruptions, we want to alert you to the likelihood of delays in responding to emails and phone calls at this time. It is possible that order processing and shipments will also be delayed. Should your project be affected, you will be notified as soon as possible. Thank you for understanding.


COVID-19 is a serious public health threat and researchers around the globe are turning to mouse models as a critical tool in viral pathogenesis, vaccine, and drug treatment discovery research. To help support these efforts, the MMRRC is distributing several COVID-19 related mouse models. To learn more about the COVID-19 related list of available strains available from the MMRRC, please visit: https://www.mmrrc.org/catalog/covid_models.php

The MMRRC is now maintaining two exciting new lines with broad applicability and interest to scientists working in many different areas. These mouse lines are called “Mouse for Actively Recording Cells 1” or MARC1. Donated by Dr. George M. Church, Ph.D., and Dr. Reza Kalhor, Ph.D., of Harvard Medical School, they are used for barcoding and lineage tracing applications in the mouse (PMID:30093604). Although these lines do not express any disease-related phenotypes, when a MARC1 mouse is crossed to mice expressing cas9 (universally or in a lineage-specific manner), combinatorial and cumulative barcoding starts in the progeny during their development, leading to developmentally barcoded animals that can be used for a multitude of applications, including lineage tracing.

The available lines are:

  • STOCK MARC1-PB7/Mmucd, RRID: MMRRC_065424-UCD, was founded by a chimeric male mouse that carried 60 homing guide RNA (hgRNA) loci scattered throughout its genome in a heterozygous state. The founder (#7) was crossed to wild-type C57BL/6J and CD1 mice initially, and the donor then used random intra-strain mating for approximately 10 generations. The genetic background of this line is deemed STOCK due to contributions from more than two inbred lines, and is a mixed background of C57BL/6J, 129S4, and CD1.

  • STOCK MARC1-PB3/Mmucd, RRID: MMRRC_065812-UCD, was founded by chimera #3 that carried 50 heterozygote germline-transmissible integrations of hgRNAs, including one on chromosome X. The selected founder was crossed with CD1 females to create the F1 generation. The donor used random intra-strain mating for approximately 12 generations prior to depositing to the MMRRC. The genetic background of this line is deemed STOCK due to contributions from more than two inbred lines and is a mixed background of CD1, C57BL/6J, and 129S4.

Please contact our customer service center at service@mmrrc.org if you have any questions about these new lines.

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Welcome to the Mutant Mouse Resource & Research Centers (MMRRC) Website

The MMRRC is the nation’s premier national public repository system for mutant mice. Funded by the NIH continuously since 1999, the MMRRC archives and distributes scientifically valuable spontaneous and induced mutant mouse strains and ES cell lines for use by the biomedical research community. The MMRRC consists of a national network of breeding and distribution repositories and an Informatics Coordination and Service Center located at 4 major academic centers across the nation. The MMRRC is committed to upholding the highest standards of experimental design and quality control to optimize the reproducibility of research studies using mutant mice. The MMRRC is supported by the Office of Research Infrastructure Programs (ORIP) in the Office of the Director at NIH. More than 50,000 mutant alleles are maintained as live mice, cryopreserved germplasm, and/or mutant ES cells. Live mice are supplied from a production colony, from a colony recovered from cryopreservation, or via micro-injection of ES cells. An MMRRC facility may offer cryopreserved material for resuscitation at the recipient scientist's institution.