As I told in a previous post, the small fruit fly (Drosophila melanogaster ) has many advantages for use as a model for understanding the genes. I told them that there are many molecular tools. Today we'll talk about one of them, GAL4/UAS system.
This system is used for targeted gene expression and was obtained nothing less than the brewer's yeast Saccharomyces cerevisiae . It works by using the transcription factor, "GAL4" (transcription factors are proteins that regulate the expression of other genes), this factor binds very specifically to a regulatory sequence that is upstream of its target genes called UAS (Upstream Activating Sequence). Thus, one can perform an intersection where the female contains a UAS sequence attached to a fluorescent marker such as GFP (Green Fluorescent Protein), which is a protein that absorbs light in the UV spectrum and emits green (This protein was obtained from the jellyfish Aequorea victory). The male, on the other hand, must contain a GAL4 associated with the promoter (the switch) of the gene of interest. Thus, the recombinant flies obtained from the F1 generation, when expressing the gene of interest, will be expressing GAL4, which will join the UAS sequence, triggering the expression of GFP. Thus, cells where the gene of interest is being expressed, shall be marked with a green fluorescent, as explained in the following scheme:
From this junction, when heterozygous parents ( the sign "+" means that the homologous chromosome is wild) can obtain animals that inherit the UAS-GFP from the mother, but not GAL4 father, therefore, there will be no element that triggers the fluorescence. Another alternative is to obtain an animal that inherits the father GAL4, but not UAS-GFP from the mother, therefore, there will be no place GAL can join and no fluorescence. The option you want, is an animal that inherits the 2 elements, and will present fluorescence in cells where the gene of interest is being expressed.
Seeing a little beyond the art, it is noteworthy to use yeast genes and proteins from jellyfish into a fly, you may ask, why is it possible?. I think already know the answer. Joseph B.
Duffy (2002) GAL4 system in Drosohila: A fly geneticist's swiss army knife. Wiley-Liss, Inc. Genesis 34:1-15
0 comments:
Post a Comment