JAX® mES Cells frequently asked questions
How is germline competency determined?
Please see our article on this topic, Germline Competency: What Does it Mean and How is it Determined?
What data do you have on the germline competency of the B6-693 mES cells?
B6-693 ES cells from have proven germ line competent in 6 experiments at passages 13, 15, 19, 31 and 32. Four of the six experiments were following ES cell targeting. Chimeric mice were obtained by unilateral transfer of 10-12 microinjected blastocysts to the uteri of ~10 pseudopregnant female mice for each experiment. In six experiments with B6 mES cells, the number of coat-color chimeras divided by the number of mice born were 10/66, 4/13, 6/15, 5/20, 21/59, 10/39. The JAX website has additional information in the tech sheet for this cell line. (.pdf)
Why has the passage number for the B6-693 mES cells changed over time?
We first distributed the B6-693 mES cells at P16. The batch was expanded from a starting population of ES cells at P12. We generated a limited number of vials at P13 and P14 for seed stock and then expanded to P16 to obtain sufficient quantities of the sellable stock. We are now distributing B6-693 mES cells at P11 that were generated with cells from a starting population at P9. This P11 line has been karyotyped male with high percentage of normal spreads.
Why is the earlier passage number advantageous?
mES cells at an earlier passage number typically have higher frequencies of germline transmission and a lower likelihood of chromosomal gains, losses or translocations (i.e. more likely to have a normal karyotype). In general, the more passages an ES cell line is subjected to, the greater the chance of changes in karyotype that could negatively impact their ability to create germline chimeras.
Why is MEK inhibitor added to the cell culture media?
The MEK inhibitor was included to ensure that cells remained undifferentiated during expansion.
