Abstract
Here, we describe a novel method based on intronic MiMIC insertions described in Nagarkar-Jaiswal et al. (2015) to perform conditional gene inactivation in Drosophila. Mosaic analysis in Drosophila cannot be easily performed in post-mitotic cells. We therefore, therefore, developed Flip-Flop, a flippase-dependent in vivo cassette-inversion method that marks wild-type cells with the endogenous EGFP-tagged protein, whereas mutant cells are marked with mCherry upon inversion. We document the ease and usefulness of this strategy in differential tagging of wild-type and mutant cells in mosaics. We use this approach to phenotypically characterize the loss of SNF4Aγ, encoding the γ subunit of the AMP Kinase complex. The Flip-Flop method is efficient and reliable, and permits conditional gene inactivation based on both spatial and temporal cues, in a cell cycle-, and developmental stage-independent fashion, creating a platform for systematic screens of gene function in developing and adult flies with unprecedented detail.
DOI:http://dx.doi.org/10.7554/eLife.26420.001
The instructions needed to build and maintain cells in an organism are encoded in their DNA. There are many different cell types, and each type only needs a small portion of the information found in the DNA to do its job. Hence, only some of the instructions, in the form of genes, need to be active or ‘expressed’ in any given cell type.
To understand how a gene works, it is necessary to know in which cell the gene is expressed and where in the cell the gene product – normally a protein – is located. Researchers may study a gene by deleting it, which prevents the protein from being made, or by attaching a new instruction into the gene, which generates a fluorescent tag on the protein to determine where and when it is expressed. Until now, it was not possible to selectively inactivate a gene and simultaneously mark both normal cells containing the protein and mutant cells lacking the protein.
Based on an existing tagging approach, Nagarkar-Jaiswal et al. have now developed a method in which normal and mutant cells of fruit flies are marked differently. A gene of interest is tagged with a fluorescent marker called green fluorescent protein (or GFP). The same gene is then inactivated in some of the cells, which are tagged with a red marker called mCherry. Nagarkar-Jaiswal et al. compared normal and mutant cells, and were able to determine how long it takes before the mutant cells become abnormal.
With this new method, the role of numerous genes in any tissue of adult flies can be reassessed. This will allow to investigate what happens when a protein is removed in specific cells in adult flies. A future goal will be to apply this method to other animals that are more closely related to humans, such as mice, to gain a clearer picture of the role of genes in different cell types and how faulty genes may cause disease.
DOI:http://dx.doi.org/10.7554/eLife.26420.002
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