Germline competency, the ability of a mouse ES cell line to contribute successfully to germ cell formation and transmit targeted genes to progeny, is a very important and desirable feature of an mES cell line. Unfortunately, it often is difficult to predict. It is typically evaluated by breeding chimeric mice that harbor a targeted mutation to wild-type mice and genotyping the offspring for the presence of the targeted gene. Factors that may reduce the probability of germline competency include the following:
- The passage number of the ES cell line (Earlier passages typically have higher germline competency because they are more likely to have a higher percentage of cells with a normal karyotype – i.e., fewer chromosomal gains, losses, or translocations.)
- The amount of stress imposed on the ES cell population by culture methods and the gene targeting process
The Jackson Laboratory distributes JAX® mES cells derived from a variety of inbred and mutant strains, but even after all the above factors are considered and all quality control protocols are followed, we can only state the probability that a targeted mES cell line will be germline competent. Given the number of variables that can affect germline competency, our goal is to provide you with high quality, low passage mES cells so you can begin your research as soon as possible. We will update the mES cell Product Specification sheets with results from germline competency trials as they become available.