When launched, Centers within the MMRRC Consortium began accepting applications from investigators to submit their mutant mouse lines for archiving and distribution. It was at this time that the variety and types of mouse lines…from those derived from ethylnitrosurea (ENU) injection into male mice, random gene and promoter trap experiments in murine ES cells, mice expressing specific recombination enzymes (CRE, FLP), to a host of new transgenic and knockout mice. Within a year, the MMRRC Program was adapting to this changing environment and broadening opportunities for acceptance of a wider variety of mouse lines by establishing three types of submissions (Table 3). Most submissions were categorized as Type 1 in which a mutant mouse line was developed and characterized by the donating investigator. Type 1 submission applications are reviewed monthly by video teleconference of a Coordinating Committee made up of the principal investigators of the Centers and ICSC and NIH program officials. These reviews are intended to determine whether an application for a Type 1 submission fulfills the following six criteria:
-
Created and analyzed using sound scientific methods;
-
Distinguishable genotypically and/or phenotypically from other publicly available lines;
-
Exhibits scientifically rigorous and experimentally reproducible findings;
-
Exists at no other public distribution repository;
-
Available for distribution without restriction to academic researchers, and
-
Controls are readily available or can be provided by the submitting investigator.
Table 3 Types of mouse submissions to the MMRRC Program Although not required, a scientific publication or readily accessible phenotype data (e.g., via a web-based resource) describing the creation and study of the submitted mouse line adds considerable scientific data and documented evidence to facilitate review. Generally, a mouse line must meet all criteria to be accepted into the MMRRC. Upon review, MMRRC ICSC staff will work with the submitting investigator to obtain additional details or provide other options for depositing into the MMRRC (e.g., Type 3 donation) if their mouse line fails to meet acceptance criteria. The only cost to the submitting investigator is that incurred by shipping mice to the assigned Center. Other than that, all importation, rederivation, quality control testing, maintenance, and archiving costs are borne by NIH funds awarded to the host institution to support the Center. For example, once imported into the Center’s repository, tissue samples are taken for DNA extraction to confirm genotype of the mutant allele and genetic background, fecal pellets are harvested (or collected earlier by the submitting investigator before shipping mice) for microbiome analysis, mice are bred (if necessary) to generate live colonies, and sperm and/or embryos are cryoarchived. Mice are listed as available for distribution by browsing or searching the online catalog once fully curated and after confirmation of gene-specific genotype and genetic background, establishment of a cryopreserved archive and verification of viable cryorecovery, determination of pathogen-free status, and exclusion of unintended or contaminating DNA elements (e.g., Cre). Proceeds derived from modest fees charged to requesting investigators to obtain and ship mouse lines to requesting investigators provides program income to support distribution costs (e.g., cryorecovery supplies, technical effort, genotyping, holding costs, etc.) incurred by the Center.
Type 2 and Type 3 submissions undergo a similar level of rigorous assessment and review yet because of their origin or other special characteristics do not go through the same formal application process as Type 1 submissions. For example, the MMRRC Program provides a very limited number of Type 2 submission “slots” that are pre-selected by NIH categorical institutes for fast-track acceptance of mice from their funded scientists into the MMRRC. Type 3 submissions are primarily secured as large, thematic collections that were produced by large consortiums, commercial organizations, and/or private research entities. Some of these collections are submitted and made available for distribution as gene-targeted ES cells, several of which have been converted into mice and are available as frozen germplasm. As a result, over time the number of Type 3 mouse lines has significantly exceeded the number of either Type 1 or Type 2 mouse lines deposited into the MMRRC (Table 4).
Table 4 Mutant mouse lines accepted into the MMRRC Program