Is there a difference between recombinant mouse LIF protein and ESGRO?
Comparing products from different manufacturers is challenging. Our customers highlighted an especially perplexing one: the difference between mouse LIF (mLIF) protein and Sigma-Aldrich’s ESGRO. Here’s a quick guide to the LIF proteins and how to swap between the two.
So, can ESGRO be replaced by recombinant mouse LIF protein and vice versa?
What is the unit conversion between mouse LIF (mLIF) and ESGRO?
10E7 units of ESGRO is equivalent to 100 µg of pure protein. A standard vial of ESGRO contains 10E6 units equivalent to 10 µg of mLIF protein. For mouse ES cell culture applications, mLIF is often used at a final concentration of 10 ng/ml, the equivalent of 1000 units/ml of ESGRO.
Buy 100 µg of LIF powder from Qkine (Qk018) (thanks Susanne and David)
Reconstitute in 100 µl ultrapure water (to obtain a concentration of 1 mg/ml)
Dilute 100x by adding 9.9 ml PBS with 0.1% w/v BSA (to obtain a concentration of 10 µg/ml)
Filter-sterilize using 0.22 µm filter (it is important to do this after dilution and addition of carrier protein to prevent loss of the protein by adsorption to the filter)
Aliquot in 552 µl aliquots
Store frozen at -20 or -80 oC
When preparing ESLIF medium, add 550 µl of the LIF solution per bottle of GMEM (dilute 1000x) to achieve a final concentration of 10 ng/ml. Note that their GMEM bottles contain 550 ml in total because they add 50 ml of FBS per bottle. Please adjust for serum-free or other volumes.
While we are here, can you use human LIF to replace mouse LIF?
For those of you working on mouse ESCs in a lab dominated by human proteins, there is good news. Human LIF can substitute for mouse LIF in feeder or feeder-free ES cell culture systems (Dahéron et al.Stem Cells22, 770–778. 2004). However, the opposite isn’t true as mouse LIF does not bind the human receptor so is inactive on human cells.
Do you have any questions or comments?
Please let us know if you’d like any of your other questions answered, have protocols to share or comments on LIF.