Genome wide analysis of transcript levels after perturbation of the EGFR pathway in the Drosophila ovary

Abstract

Defects in the epidermal growth factor receptor (EGFR) pathway can lead to aggressive tumor formation. Activation of this pathway during normal development produces multiple outcomes at the cellular level, leading to cellular differentiation and cell cycle activation. To elucidate the downstream events induced by this pathway, we used genome-wide cDNA microarray technology to identify potential EGFR targets in Drosophila oogenesis. We focused on genes for which the transcriptional responses due to EGFR pathway activation and inactivation were in opposite directions, as this is expected for genes that are directly regulated by the pathway in this tissue type. We perturbed the EGFR pathway in epithelial follicle cells using seven different genetic backgrounds. To activate the pathway, we overexpressed an activated form of the EGFR (UAS-caEGFR), and an activated form of the signal transducer Raf (UAS-caRaf); we also over-or ectopically expressed the downstream homeobox transcription factor Mirror (UAS-mirr) and the ligandactivating serine protease Rhomboid (UAS-rho). To reduce pathway activity we used loss-of-function mutations in the ligand (gurken) and receptor (torpedo). From microarrays containing 6,255 genes, we found 454 genes that responded in an opposite manner in gain-of-function and loss-of-function conditions among which are many Wingless signaling pathway components. Further analysis of two such components, sugarless and pangolin, revealed a function for these genes in late follicle cell patterning. Of interest, components of other signaling pathways were also enriched in the EGFR target group, suggesting that one reason for the pleiotropic effects seen with EGFR activity in cancer progression and development may be its ability to regulate many other signaling pathways. Developmental Dynamics 232:709 -724, 2005.

New Negative Feedback Regulators of Egfr Signaling inDrosophila

“…Table 1 shows the top 25 transcripts upregulated by Egfr ACT , and Table 2 shows the top 25 transcripts upregulated by Egfr DN [the full set is shown in Table S1 and the primary data have been submitted to GEO (GSE34872)]. Eight of these genes were also identified in other studies that conducted whole-genome transcriptional analysis of the Egfr pathway or the Ras gene, which functions downstream of Egfr (Tables 1 and 2) (Asha et al 2003;Jordan et al 2005;Firth and Baker 2007). Five known target genes were also represented within the top group of 25 genes upregulated by Egfr: ventral veinless (vvl) (de Celis et al 1995;Llimargas and Casanova 1997), sty (Hacohen et al 1998;Casci et al 1999), pnt (O'Neill et al 1994Gabay et al 1996), MASK (Smith et al 2002), and Mkp3 (Kim et al 2003;Rintelen et al 2003;Gomez et al 2005).…”

Krüppel homolog 1 (Kr-h1) mediates juvenile hormone action during metamorphosis of Drosophila melanogaster

“…The lack of BR expression in these cells may be due to the lack of Wg signal. Wg signaling has been shown to be required for BR expression in the follicle cells of the dorsal appendage primordia of egg chambers (Jordan et al, 2005;Ward et al, 2006). However, the loss of br expression in the cells in the p2 region is not likely to be caused by lack of Wg signal, because Wg is present at higher levels in the p2 region than in the p1 region where BR is expressed (Lawrence et al, 2002).…”

Capicua regulates follicle cell fate in theDrosophilaovary through repression ofmirror

“…Recent microarray analysis has identified a number of genes that are regulated by mirr overexpression or alterations in Egfr signaling and that therefore represent potential Mirr targets (Jordan et al, 2005). Mirr also appears to regulate cell affinity, as mirr mutant clones in the eye exhibit a round shape (Yang et al, 1999).…”