Regulation of the feedback antagonist naked cuticle by Wingless signaling

Area of Science:

• Developmental biology
• Molecular genetics
• Signal transduction

Background:

• Signaling pathways typically regulate gene expression in a cell-type-specific manner.
• Pathway-specific feedback antagonists can broaden signal response across cell types.
• The Wingless (Wg) pathway activates the naked cuticle (nkd) gene broadly in Drosophila.

Purpose of the Study:

• To investigate the regulatory mechanisms underlying the broad Wg-mediated activation of the nkd gene.
• To identify specific DNA elements responsible for nkd gene responsiveness to Wg signaling.

Main Methods:

• Analysis of the nkd locus in cell culture to identify Wg response elements (WREs).
• In vivo studies in Drosophila to assess the function of WREs in embryonic and larval tissues.
• Utilized transcription factor TCF for pathway activation analysis.

Main Results:

• Identified Wg response elements (WREs) within the nkd locus that are directly activated by Wg signaling via TCF.
• Demonstrated that these WREs are activated in multiple, distinct, and overlapping patterns across different tissues.
• Found WREs to be necessary and largely sufficient for nkd expression in late larval stages, contributing partially to embryonic expression.

Conclusions:

• nkd gene's broad responsiveness to Wg signaling is mediated by multiple WREs with broad, though not universal, activation patterns.
• The presence of several WREs likely facilitated the conservation of the Wg-Nkd feedback circuit during Wg pathway evolution.