Generating Inbred Rats
The main strategies for generating inbred rats are the same as those for inbred mice.
A strain is defined as inbred when it has been mated brother x sister for 20 or more consecutive generations (F20). All offspring can be traced back to a single ancestral breeding pair in the 20th or subsequent generation. Such inbred strains are therefore isogenic (genetically identical).
Substrains are branches of an inbred strain that are either known or suspected to be genetically different from that inbred strain. They form under any of the following three conditions: 1) branches of a strain are separated from the parent colony before the 40th generation of inbreeding; 2) a branch of a strain is maintained separately from the parent colony for more than 20 generations of inbreeding (10 generations in the branch and 10 in the parent colony); and 3) genetic differences from the parent colony are discovered. Unfortunately, the degree of genetic diversity among substrains is often not well characterized.
Complex strategies for inbred rat model development
Inbred strains, and their substrains, can be used to create ever-increasingly complex genetic backgrounds to be used as a model for human biology. Introduction to some of these advanced strategies offers guidance on the possibilities, which include congenic and recombinant inbred strains, and many more. Explorations and characterizations of suitable inbred model rats will be available from the Rat Genome Database (RGD) and The National BioResource Project. These resources may help researchers to evaluate and explore complex systems on suitable rat models, or may help researchers design breeding strategies of their own to accomplish their goals.
It is crucial to understand the rules of nomenclature for animal strains so that the users of the models are able to understand the genetic background as fully as possible. Additional information about the nomenclature standards can be found in the section on Breeding Rats.
See also: About Inbred Rats for more general information on inbred rats.