We visualized the activity of transcription regulatory sequences during aging by using the enhancer-trapping technique in which an artificial exogenous genetic construct encoding the yeast transcription factor GAL4 (GAL4 driver) is expressed under the control of natural endogenous regulatory elements (enhancers)(O'Kane and Gehring, 1987;Brand and Perrimon, 1993). These GAL4 flies are crossed with a UAS-lacZ reporter line to express the E.coli enzyme ß-galactosidase. Since the level of ß-galactosidase activity reflects the level of ß-galactosidase mRNA (Simon and Lis, 1987), we can indirectly follow the temporal and spatial changes of the transcriptional activity of the genomic region surrounding the GAL4 insertion over the fly life span. By using a collection of GAL4 drivers (newly generated in our lab or from Stock Centers), we can examine the activity of a multitude of genomic regions as a function of age. 
This work is described in Aging Cell (2002) 1,47-56Abstract Full text
The GAL4 driver lines collection is described in Genesis (2002) 34,34-38Full text