In article <mit.edu-2911951015050001 at cancer-ctr-mac-7.mit.edu>, mit.edu (k)
> I am utilizing the Tet inducible (repressable) system for conditional gene
> expression developed by Gossen and Bujard. I've found that lines which
> initially showed inducible expression of the desired gene eventually cease
> to induce these genes after several passages. Anyone else seen these?
Are you using lines cloned from a single transfected cell, or bulk
cultures? If bulk, it's not very surprising. What cells are you using?
Some cells like to spit out genes more rapidly than others. What gene are
you expressing? If it's toxic to the cells, even a very low level of
baseline expression will select in favor of cells that do not express the
gene. Are you using the inducible or repressible transactivator? If it's
the inducible, remember tetracycline is not particularly stable in aqueous
media so your loss of expression might be due to insufficient tet in the
You need to supply us with a little more information!!
Ian Davis iddavis at vms.cis.pitt.edu
University of Pittsburgh Cancer Institute