1(2)gl gene regulates late expression of segment polarity genes in Drosophila

Cooperative regulation of cell polarity and growth by Drosophila tumor suppressors

Loss of cell polarity and tissue architecture are characteristics of malignant cancers derived from epithelial tissues. We provide evidence from Drosophila that a group of membrane-associated proteins act in concert to regulate both epithelial structure and cell proliferation. Scribble (Scrib) is a cell junction-localized protein required for polarization of embryonic and, as demonstrated here, imaginal disc and follicular epithelia. We show that the tumor suppressors lethal giant larvae (lgl) and discs-large (dlg) have identical effects on all three epithelia, and that scrib also acts as a tumor suppressor. Scrib and Dlg colocalize and overlap with Lgl in epithelia; activity of all three genes is required for cortical localization of Lgl and junctional localization of Scrib and Dlg. scrib, dlg, and lgl show strong genetic interactions. Our data indicate that the three tumor suppressors act together in a common pathway to regulate cell polarity and growth control.

Spatial expression of the hsr-omega (93D) gene in different tissues of Drosophila melanogaster and identification of promoter elements controlling its developmental expression

Developmental expression of the heat shock inducible non-protein coding hsr-omega gene in several larval and adult tissues of Drosophila melanogaster was examined by in situ hybridization to transcripts in intact organs and by X-gal staining in the germline transformants and carrying the lacZ reporter gene under the control of hsr-omega promoter. This gene is expressed in a specific spatial pattern in all the larval and adult tissue types examined; however, its transcripts were specifically absent in certain gonadal cell types like the male as well as female gonial cells and in follicle cells and oocytes in ovary. All polytenised tissues like the prothoracic and salivary glands, certain regions of larval gut and the Malpighian tubules showed a greater abundance of hsr-omega transcripts with a strong hybridization in nuclei. Our results with promoter deletion variant germline transformants suggest that a region between -346bp to -844bp upstream contains major regulatory elements for developmental expression of this gene in most of the larval and adult tissues examined; however, this region is not sufficient for its normal expression in male and female reproductive systems. An analysis of the base sequence of the hsr-omega promoter (upto - 844 bp) reveals putative ecdysone receptor element half-sites and two GAGA factor binding sites which may be involved in its developmental expression and its ready inducibility. The widespread expression in most tissue types and the known lethality associated with its homozygous deletion, suggest that the variety of non-protein coding transcripts of the hsr-omega gene have vital "house-keeping" functions.