A tissue-specific transcription enhancer from the Drosophila yolk protein 1 gene

The yolk protein 1 gene (yp1) of Drosophila melanogaster is expressed only in the ovarian follicle cells and the fat bodies of adult females. We have previously shown that a different cis-acting DNA region is required for each of these tissue specificities. In this paper we use germ line transformation to localize and characterized one of these tissue-specific regulatory regions. We demonstrate that a 125 bp segment of DNA located 196 bp upstream of the yp1 cap site is sufficient to determine the sex-, stage-, and fat body-specific expression of the yp1 gene. We also find that this region can confer yp1-specific expression on a heterologous Drosophila promoter. This specificity is retained when the region is in different orientations and at different distances from the heterologous promoter. Thus a small regulatory region acts in vivo as a positive enhancer to determine the fat body expression pattern of yp1.     

Taste sensitivity in homeotic mutants of the drosophila leg-arista-wing complex

It is well established that taste chemoreceptors in Drosophila are located on the tarsi of the first leg pair. In order to investigate the influence of the novel homeotic arista-tarsus transformation on behavior, an analysis of taste perception in the lawc-mutants, characterized by the transformation of the arista into tarsus elements, was carried out. The data were subjected to thorough statistical treatment. It was shown that elements of an additional leg that appeared as a result of homeotic transformation of the arista were sensitive to gustatory stimuli. Analysis of the innervation of the homeotic organs by means of cobalt staining of afferent projections showed that the afferents starting from the homeotic leg reached the thoracic ganglion.     

Targeted gene transfer system using a streptavidin-transforming growth factor-alpha chimeric protein.

The previously reported streptavidin-TGFalpha chimeric protein-based delivery system (Ohno and Meruelo, DNA Cell Biol. 15:401-406, 1996) could efficiently transfer protein molecules into A431 cells via the epidermal growth factor (EGF) receptor. We have modified this delivery system for the transfer of DNA. For this purpose, we have linked the chimeric protein ST-TGFalpha to DNA through biotinylated polylysine molecules. We show with this system, in the presence of the endosome-destabilizing reagent chloroquine, an average of 50-fold increase in reporter gene expression in comparison with polylysine DNA complexes alone. This gene expression is specific for EGF receptor-expressing cells and is blocked by EGF-binding molecules. These results suggest that the ST-TGFalpha biotinylated polylysine system could be used to deliver DNA to targeted cells.     

Targeted mutagenesis and genetic analysis of a Drosophila receptor-linked protein tyrosine phosphatase gene

Several Drosophila receptor-linked protein tyrosine phosphatases (R-PTPs) are selectively expressed on axons of the developing embryonic central nervous system. The extracellular domains of these axonal R-PTPs are homologous to neural adhesion molecules. Thus, R-PTPs may directly couple cell recognition to signal transduction via control of tyrosine phosphorylation. To examine the function of these molecules during nervous system development, we wished to generate mutations in R-PTP genes. It was unclear whether a mutation in a single R-PTP gene would confer lethality, however, because the similarities in sequence and expression pattern between the axonal R-PTPs suggest that they may have partially redundant functions. To circumvent this problem, we developed a directed mutagenesis strategy based on local transposition of P elements, and used this approach to isolate a null mutation in the DPTP99A gene. This strategy, which we describe in detail here, should be applicable to any Drosophila gene within a lettered division of an appropriately marked P element. Flies lacking DPTP99A expression are viable and fertile, and we have been unable to detect any alterations in the embryonic nervous system of DPTP99A embryos using a variety of antibody markers.