MEF cells serve as feeder cells that support the growth of undifferentiated mouse or human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). MEF cells are isolated from 13.5-day old mouse embryos and should be used at early passages. Before use as feeder cells, MEF cells must be mitotically inactivated by γ-irradiation or mitomycin-C treatment.
DR4 MEF cells are derived from mice that are genetically engineered with 4 drug-resistant genes, neomycin, hygromycin, puromycin and 6-thioguanine.

Treatment:
gamma-irradiated

Cell Type:
Mouse Embryonic fibroblasts

Storage and Stability:
For long-term storage, aliquot to avoid repeated freezing and thawing and Store in liquid nitrogen. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Aliquots are stable for 6 months.

Protocol:
1. Remove a vial of frozen cells from liquid nitrogen and place it onto dry ice for 5’ before thawing it at 37ºC water bath. As soon as the majority of the content of the vial thawed, transfer it to a conical tube containing 10x volume of pre-warmed medium.

2. Spin at 1000 rpm for 5 min, discard medium, resuspend the cells in growth medium and plate them at an appropriate density in a gelatin-coated tissue-culture dish (generally 25,000-50,000 cells/cm2, Appendix III). Optimal density is to be determined by the user for specific applications.