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Temporal control of the UAS/GAL4 system has been achieved by replacing GAL4 with the Gene-Switch protein, which is a chimeric GAL4 protein that contains the GAL4 DNA binding domain, the human progesterone receptor ligand-binding domain and the activation domain from the human protein p65 ( Osterwalder et al., 2001 Roman et al., 2001). However, many have been characterized and are suitable to manipulate gene expression in aging adults ( Seroude, 2002 Seroude et al., 2002 Shen et al., 2009).īecause most promoters and enhancers that drive GAL4 expression are active at multiple stages of development, temporal control of transgene expression is impossible with the UAS/GAL4 system.
Gene expression c artoon drivers#
The majority of the GAL4 drivers available are solely useable during the pre-adult stages because the expression pattern of GAL4 across the life span of the adult is generally ignored, despite the fact that both the magnitude and localization of expression can change with age ( Seroude et al., 2002).
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Since its introduction, thousands of GAL4 lines (GAL4 drivers) have been generated. The most widely used expression system is the UAS/GAL4 system in which the EG uses a promoter containing upstream activating sequences (UAS) and the TA is the yeast transcription factor GAL4 that can be controlled by an enhancer-trap or a Drosophila promoter ( Brand & Perrimon, 1993). Thus, the expression pattern of the EG is indirectly controlled by the nature of the promoter directing TA expression. The expression of the effector gene is controlled by a promoter, which is regulated by the transactivator. Various inducible-gene expression systems are available in Drosophila, the majority of which require the use of two distinct transgenic constructs containing respectively an effector (EG) and a transactivator (TA) gene ( Venken, Simpson & Bellen, 2011). Inducible gene expression systems, which allow for the temporal and spatial regulation of expression of a gene of interest, have been successfully employed in identifying and studying genes that influence aging in the model organism Drosophila melanogaster ( Poirier & Seroude, 2005). The ability to make targeted gene manipulations is crucial to the investigation of biological phenomena and is the hallmark of modern genetics. This study reveals that the repressive ability of GAL80 is affected by the age and sex of the animal which is a major limitation to regulate gene expression with GAL80 in aged Drosophila. The inhibition of GAL4 activity and the maintenance of induced expression are altered in old animals. Upon treatment of newly emerged adults with tetracycline, induction of GAL4 activity is observed but the level of induction is influenced by the concentration of the inducer, the age, the sex and the anatomical location of the expression. Almost complete inhibition of the expression of UAS transgenes during the pre-adult stages of the life cycle is obtained by using four copies and two types of Tet-off GAL80 transgenes. By placing GAL80 under the control of a Tet-off promoter, GAL4 activity is regulated by the presence or absence of tetracycline in the diet. This study constructed and characterized Tet-off GAL80 transgenes designed to allow temporal control of GAL4 activity in aging adult muscles. However, the ability to control the temporal activity of GAL4 with this system is very limited. The UAS/GAL4 system is the most used method in Drosophila melanogaster for directing the expression of a gene of interest to a specific tissue.