This approach allows the CoRE to rapidly generate GEMMs with diverse genome modifications such as humanization, large insertion, conditional knockout, base substitution, and deletion. The CoRE designs CRISPR guides and repair donors (oligonucleotide, long single-stranded DNA, double-stranded DNA or rAAV), which are synthesized in-house or procured through external vendors. Potential founder (F0) mice are produced by delivering the editing reagents into zygotes with electroporation or microinjection. F0 mice are thoroughly genotyped via our comprehensive genotyping service, and selected F0 mice are bred with wild-type mice for germline transmission. The CoRE offers N1 breeding service and confirmed heterozygous mice are transferred to investigators.

We offer microinjection of purified DNA constructs for the production of transgenic mice. Investigators provide midi- or maxi-prep DNA digested with appropriate restriction enzyme(s), and the CoRE gel-purifies a desired DNA fragment suitable for microinjection. A minimum of two transgenics or 30 live births or embryos, whichever comes first, is prepared for each set of injections charged to an investigator.

The CoRE provides microinjection of an embryonic stem (ES) cell clone into mouse blastocysts to establish chimeric mice to produce knockout mouse lines. Investigators provide targeted ES cells suitable for chimera production on the day of blastocyst injection.

The long-term storage of mouse sperm and/or embryos reduces the need for constant maintenance of lines not essential for current research needs, as well as providing a backup repository of important lines in case of environmental or weather-related crises. To minimize losses in the case of a freezer failure, cryopreserved sperm samples are maintained in two separate locations.

Cryopreserved sperm samples can be shipped from Mount Sinai to collaborators around the world. This service includes the preparation and loading of dry liquid nitrogen shippers with frozen sperm samples.

The CoRE recovers lines from which sperm have been frozen and stored at the Icahn School of Medicine at Mount Sinai.

Mouse lines can be imported into the Icahn School of Medicine at Mount Sinai by obtaining one to two males from a collaborator at another institution. These males are used to prepare sperm for <em>in vitro</em> fertilization of wild-type mouse oocytes. Alternatively, frozen sperm can be imported instead of live animals and used for <em>in vitro</em> fertilization. The fertilized embryos are transferred to specific pathogen-free hosts to generate clean mice. The CoRE also works with investigators to import lines of mice into Mount Sinai through frozen early-stage embryos. In addition, in-house mouse lines infected with various mouse pathogens may be cleaned by transferring embryos to pathogen-free hosts.

The CoRE can develop a PCR-based assay based on absence-presence of an amplicon and/or Sanger sequencing to genotype mouse tissues. The CoRE extracts genomic DNA, runs PCR/agarose gel and, if requested, purifies and sequences the PCR product.

The CoRE can provide mouse embryos at various preimplantation stages. In addition, the CoRE can perform timed matings with new lines created in-house to produce embryos for rapid characterization.

Investigators provide 6-10 homozygous male mice to be mated with superovulated wild-type females. Heterozygous embryos are collected and transferred to surrogate females. Resulting female progeny are superovulated and bred to the same homozygous males. Embryos are collected and transferred to surrogate females, leading to production of a large number of homozygous and heterozygous mice. Other strategies, such as IVF, may be utilized to suit the investigator's needs.