Capicua regulates follicle cell fate in theDrosophilaovary through repression ofmirror

Abstract

The dorsoventral axis of the Drosophila egg is established by dorsally localized activation of the epidermal growth factor receptor (Egfr)in the ovarian follicular epithelium. Subsequent positive- and negative-feedback regulation generates two dorsolateral follicle cell primordia that will produce the eggshell appendages. A dorsal midline domain of low Egfr activity between the appendage primordia defines their dorsal boundary, but little is known about the mechanisms that establish their ventral limit. We demonstrate that the transcriptional repressor Capicua is required cell autonomously in ventral and lateral follicle cells to repress dorsal fates, and functions in this process through the repression of mirror. Interestingly, ectopic expression of mirror in the absence of capicua is observed only in the anterior half of the epithelium. We propose that Capicua regulates the pattern of follicle cell fates along the dorsoventral axis by blocking the induction of appendage determinants, such as mirror, by anterior positional cues.

Ras signaling modulates activity of the ecdysone receptor EcR during cell migration in the drosophila ovary

“…As well, br loss-of-function and overexpression in the FC indicate a role in both eggshell formation and amplification at chorion protein loci (Tsolovsky et al, 1999a). Our data show that EcR does not regulate BR in the FC during late oogenesis, an outcome consistent with both the distinct patterns of EcR activity and BR-C expression, and previous work showing that Br-C is regulated by grk pathways during late stages of oogenesis (Buszczak et al, 1999;Atkey et al, 2006). Thus BR may mediate independent signals to regulate chorion gene amplification.…”

“…During late oogenesis, expression of putative EcR target genes Eip74EF, Eip75B, and Br-C implies that the hierarchy is active in the FC (Deng and Bownes, 1998;Bryant et al, 1999a;Buszczak et al, 1999;Tzolovsky et al, 1999a;Carney and Bender, 2000;Atkey et al, 2006). As well, the regulation of chorion gene expression by usp and amplification by broad point to a late function for EcR in eggshell patterning (Shea et al, 1990;Oro et al, 1992;Tsolovsky et al, 1999a,b).…”

Feedback control of the EGFR signaling gradient: superposition of domain-splitting events inDrosophilaoogenesis

“…Later, BR expression increases in the two prospective roof domains and remains stable throughout subsequent appendage morphogenesis (Dorman et al, 2004;James and Berg, 2003). Both the midline repression of BR and its upregulation in the prospective roof cells depend on the RAS/MAPK pathway, which is stimulated by activated EGFR (Atkey et al, 2006;Yakoby et al, 2008b).…”

Gene regulation during Drosophila eggshell patterning

“…Work over the past decade has identified the transcriptional factors that control these genes and has started to connect them in a regulatory network (2,(12)(13)(14)(15)(16)(17)(18). Based on this network, we can predict how the expression patterns of multiple genes will respond to a range of genetic perturbations, including the quantitative changes in the distribution and levels of inductive signals (Fig.…”

“…The induction threshold for the repressor is higher than that for br, which explains why it is expressed only in cells exposed to intermediate levels of GRK. The activating part of the feedforward loop is mediated by the Iroquois transcription factor Mirror (MIRR), and the repressive part relies on the ETS-domain factor Pointed (PNT) (12,13,15,22). Given the dorsoventral pattern of the EGFR activation by GRK ( Fig.…”