I had similar problems which could hint that GFP is toxic to cells. I
prepared several fusion proteins driven by an CMV promoter and expressed
them in NIH 3t3 cells. As long as the expression was transient I got brigh
green cells. When cotransfecting with a neo resistance construct many cells
were again bright green. Selection with G-418 yielded many colonies none of
them green. A control with b-gal showed that the cotransfection was OK.
A colleague who encountered a similar problem treated his cells with Sodium
butirate which activates inactive chromatin. Upon such treatment the cells
regained their fluorescence.
Has anybody been successful in preparing stable cell lines expressing GFP ?
Concerning FACS analysis of GFP expressing cells - this has been done in
our institute and the best person to ask is Mr. Derek Davies from our FACS
lab tel 0171-269-3394, Fax 0171-405-1556 (UK).
Hope this was of some help or consolation