FIaxtion of GFP

[Derya is an idiot]

I generated GFP knockin mice. I found GFP fluorescence disappears after
freeze-thaw, unless pretreated with 4% paraformaldehyde. However, such
fixation will destroy/mask the cell surface epitope. Therefore, I can
not do staining for cell surface markers.

Does anyone have any experience on this?

Thanks.