Genetic Modifier Screens on Hairless Gain-of-Function Phenotypes Reveal Genes Involved in Cell Differentiation, Cell Growth and Apoptosis in Drosophila melanogaster

Abstract

Overexpression of Hairless (H) causes a remarkable degree of tissue loss and apoptosis during imaginal development. H functions as antagonist in the Notch-signaling pathway in Drosophila, and the link to growth and apoptosis is poorly understood. To further our insight into H-mediated apoptosis, we performed two large-scale screens for modifiers of a small rough eye phenotype caused by H overexpression. Both loss-and gain-of-function screens revealed known and new genetic interactors representing diverse cellular functions. Many of them did not cause eye phenotypes on their own, emphasizing a specific genetic interaction with H. As expected, we also identified components of different signaling pathways supposed to be involved in the regulation of cell growth and cell death. Accordingly, some of them also acted as modifiers of proapoptotic genes, suggesting a more general involvement in the regulation of apoptosis. Overall, these screens highlight the importance of H and the Notch pathway in mediating cell death in response to developmental and environmental cues and emphasize their role in maintaining developmental cellular homeostasis.

Alternative Requirements for Vestigial, Scalloped, and Dmef2 during Muscle Differentiation inDrosophila melanogaster

“…We also tested the muscle-specific expression of two different well-characterized reporter constructs that express ␤-galactosidase (␤-gal) under the control of sd enhancers. sd ETX4 animals have an enhancer-trap (␤-gal) P-element construct inserted into the 5Ј regulatory region of the sd locus and have been used extensively to obtain the pattern of sd expression in embryo and other tissues (Campbell et al, 1992;Deshpande et al, 1997;Varadarajan and VijayRaghavan, 1999;Muller et al, 2005). Similar to what we observe with FISH detection of the sd signal, in sd ETX4 embryos, significant levels of ␤-gal can be detected in some muscle cells (Figure 2A).…”

A Screen for Modifiers of Notch Signaling Uncovers Amun, a Protein With a Critical Role in Sensory Organ Development

“…Since loss of cone cells results from decreased Notch signaling, these results suggest that Amun function potentiates Notch signaling required for cone cell induction in the developing Drosophila eye. This interpretation is further corroborated by the observation that overexpression of Amun mediated by EP(X)1503 suppresses inhibition of Notch signaling that results from Hairless overexpression in the eye (Muller et al 2005).…”

“…The distribution among functional categories of gene(s) potentially affected by these modifying transposons is summarized in Table 2. The 30 transposon insertions associated with cell-cell communication proteins include genes encoding known Notch pathway members (e.g., numb, kuzbanian; Bray 2006), as well as genes that have been recovered previously from Notch-based screens, such as patched, Ras85D, and puckered (Rottgen et al 1998;Muller et al 2005;Mahoney et al 2006). We also identified genes encoding a number of cell-cell communication proteins not previously implicated in Notch signaling, such as the phosphatase Gilgamesh, the two immunoglobulin superfamily members Fasciclin 2 and ImpL2, and the two hormone-receptor-like genes Hr38 and Hr39.…”

“…Overexpression of CG2446 in both genetic backgrounds resulted in various bristle phenotypes, including shaft-to-socket transformations and development of supernumerary macrochaetae. In a second screen, EP(X)1503 was recovered as a suppressor in a Hairless gain-of-function screen designed to identify modifiers of a small rough-eye phenotype caused by GMR-driven Hairless (Muller et al 2005). We find that P{XP}d03329 not only mildly suppresses the GMR.DlWT/1 cone cell phenotype (see below), but also suppresses the 34B.DeltaDICD wing vein-thickening phenotype ( Figure 2D) and enhances the C96.DeltaDICD wing notching phenotype (data not shown).…”

Signalling Pathways in Development and Human Disease: A Drosophila Wing Perspective

“…In these cases, the screen aims to identify genes belonging to a pre-determined set of interacting genes. Some examples of successful screens aiming to identify members of known signalling pathways are those targeting the Sevenless and EGFR (Karim et al, 1996;Huang and Rubin, 2000;Taguchi et al, 2000;Rebay et al, 2000), Notch (Verheyen et al, 1996;Go and Artavanis-Tsakonas, 1998;Muller et al, 2005a), Dpp (Raftery et al, 1995;Chen et al, 1998;Su et al, 2001), JAK/STAT (Bach et al, 2003;Mukherjee et al, 2006), Hh (Haines and van den Heuvel, 2000;Collins and Cohen, 2005), TNF (Geuking et al, 2005) and Wnt (Greaves et al, 1999;Cox et al, 2000;Desbordes et al, 2005) pathways. Although the use of genetic screens in vivo has many advantages, they are time-consuming and difficult to escalate genome-wide.…”