CD-1 mice represent a widely used model in scientific research. These albino laboratory mice are an “outbred stock,” distinguishing them from genetically uniform strains. They are recognized for their broad applicability as a general-purpose mammalian model. Their widespread adoption reflects their utility across various experimental designs and research objectives.
Origin and Genetic Makeup
CD-1 mice trace their lineage to a non-inbred Swiss mouse colony, developed by Charles River Laboratories. The original founders, consisting of two male and seven female albino mice, were imported into the United States in 1926 from a laboratory in Lausanne, Switzerland, by the Rockefeller Institute. Descendants of these mice led to the establishment of the Ha/ICR stock in 1948 at the Institute for Cancer Research, and Charles River Laboratories acquired their breeding nucleus in 1959.
An “outbred stock” refers to a population of laboratory animals where mating is intentionally managed to maximize and maintain genetic variation. This breeding strategy ensures that the resulting mice exhibit heterozygosity at numerous gene loci. This approach differs from “inbred strains,” which are developed through extensive brother-sister matings to produce genetically identical individuals. Charles River Laboratories employs an International Genetic Standardization (IGS) system to maintain consistent genetic diversity across their global colonies.
Distinctive Physiological Traits
CD-1 mice are albino. They are known for their robust health and general hardiness, allowing them to adapt well to various laboratory environments. This resilience contributes to their reliability within experimental settings.
A particularly significant biological characteristic of CD-1 mice is their high fecundity. The average litter size for CD-1 mice can be around 11.5 pups. Coupled with strong maternal instincts, this supports pup survival and efficient colony maintenance. Such reproductive vigor inherently makes them a cost-effective and readily available model for large-scale studies.
Common Research Applications
The widespread use of CD-1 mice spans various research fields due to their adaptable nature. In toxicology and safety studies, their consistent health baseline and inherent genetic diversity make them suitable for assessing the effects of new compounds. They are employed to test novel drugs and chemicals, evaluating potential human health risks from both acute and chronic exposure. Their robust health enables long-term studies, providing insights into the cumulative impacts of various substances.
CD-1 mice are also valuable in pharmacology for initial drug screening and identifying potential therapeutic agents. They serve as a general model for investigating fundamental biological processes, including aging, oncology, immunology, and vaccine development. Their efficient breeding and large litter sizes make them particularly useful for mouse transgenesis experiments. Additionally, CD-1 mice function as sentinel animals in research facilities, monitoring colony health and detecting potential pathogens.
The Outbred Model in Study Design
The decision to use CD-1 mice in a study design often hinges on their unique genetic diversity, which presents both advantages and considerations. This inherent variability is beneficial when researchers aim to model a response across a genetically varied population, more closely resembling the diversity found in humans. They are valuable in initial safety testing, helping researchers understand a range of individual responses to compounds.
However, this genetic variability can challenge studies requiring high precision and tight control over genetic factors. When experimental outcomes need to be attributed to specific genetic influences, the differences between individual CD-1 mice can introduce confounding variables. For such research, genetically uniform inbred strains are typically chosen for their controlled and reproducible results. Nevertheless, outbred stocks like CD-1 mice offer practical advantages, including superior breeding performance and lower costs, making them a practical choice for many general investigations.