Future unsolicited competing continuation applications will compete with all investigator-initiated applications and will be reviewed according to the customary peer review procedures. However, the specific number of awards will depend upon the scientific merit and scope of the applications received and the availability of funds. The laboratory mouse is presently the most widely used, available, and economical animal model used in biomedical research and, in particular, transgenic research. In addition to the many traditional mutant mouse strains, hundreds of additional strains of mice have been created in recent years through transgenic technology. The methods presently available to preserve, maintain, and produce this proliferating number of strains include active breeding programs and embryo cryopreservation.
Breeding is expensive and often duplicative.
Cryopreservation of embryos is less expensive, but is technologically intensive and heavily dependent on mouse husbandry. These handicaps are clearly resulting in the loss of many strains and limiting access to other users. The development of refined technology for harvesting and successfully cryopreserving mouse sperm and reconstitution of strains through in vitro fertilization or artificial insemination and relatively simple breeding procedures offer a very promising alternative to the current situation. An NCRR-sponsored conference on Development of Transgenic Animal Model Resources was held in November 1990. This conference recommended the development of transgenic technology and cryopreservation of transgenic embryos and sperm.