We prepare brain slice cultures from animals expressing EGFP/EYFP in specific neurons. As the mouse strains are heterozygous, we need to find out whether an animal is a carrier or not. To do so, so far we run, first or second slice in dish, from the sterile hood to the electrophysiology setup next door eqipped with epifluorescence hardware. This is quite inefficient, so I'm looking into alternatives. Does anyone have experience with the FMA-04 system by BLS (Hungary), or any other small and inexpensive system for the purpose of detecting EGFP/EYFP fluorescence? (The goggles by BLS don't seem to be suited for our purposes, as the fluorescence is too weak).
I used to genotype transgenic animals visually, like you describe. I found that some transgenic animals could be genotyped as pups (immediately before having fur), by using a UV torch and goggles. Their whole bodies would have a (very) slight green hue, with the brain visible inside the skull and somewhat more fluorescent. This depends, of course, on the promoter of the transgene - can you reveal which promoters you are working with? I also noted that when slicing on a vibratome, fluorescence would often be immediately visible without a specific excitation source or goggles. So you must indeed have very low levels of fluorescence, if you cannot see it with a magnifying lens, a UV light and filter goggles.
I am afraid I dont have experience with the FMA-04 system you mention.
Jan, thanks for sharing your experience!
We have a mouse strain expressing EGFP in a subset of somatostatin-positive neurons (the so-called X98 strain, Ma et al. J Neurosci 2006, 26(19):5069–5082; official strain name is Tg(Gad1-EGFP)98Agmo/J). Because of the low number of neurons expressing EGFP these mice are certainly at the lower end of EGFP detectability. It is these on which I tested the goggles. Another strain expresses EYFP under the control of the ChAT promoter (B6.Cg-Tg(Chat-COP4*H134R/EYFP,Slc18a3)6Gfng/J); my impression is that these mice have more neurons expressing EYFP throughout the whole brain. I did not test any goggles on them, but your account suggests that maybe I could give it another try. The observation of spontaneous fluorescence immediately after slicing is intriguing - I guess it is visible only in complete darkness?
Unfortunately I do not have experience with any of your strains myself, but if you have it available, I would take a look at the pups with UV torch and goggles when they are 4-6 days old, to see if you have any indication of fluorescence.
The fluorescence during slicing is visible under normal vibratome work light (I guess standard fluorescent light bulb), without any goggles or anything. It looks a bit like when there is oil on water, and you see a greenish reflection on the surface. It may well be you don't see this phenomenon with weakly fluorescent slices, but maybe with a magnifying glass and UV light + goggles.
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