Uncoupling cadherin-based adhesion from wingless signalling in Drosophila

Area of Science:

• Developmental Biology
• Cell Biology
• Molecular Biology

Background:

• Wnt genes encode secreted glycoproteins vital for intercellular communication during development.
• Wingless (Drosophila Wnt-1 homologue) signaling involves Armadillo (beta-catenin homologue), a component of the cadherin/catenin complex at adherens junctions.
• The interplay between Wingless and Armadillo suggests concurrent control of cell fate specification and cell-cell adhesion.

Purpose of the Study:

• To investigate whether Wingless specifies cell fate solely by modulating cell adhesion or if it signals independently of adherens junctions.
• To differentiate between these two models of Wingless action.

Main Methods:

• Overexpression of full-length Drosophila E-cadherin and a dominant-negative truncated form.
• Analysis of Wingless phenotypes resulting from E-cadherin manipulation.
• Assessment of Armadillo localization and function.

Main Results:

• Overexpression of both E-cadherin constructs mimicked Wingless phenotypes, uncoupling adhesion changes from signaling effects.
• Demonstrated that both constructs titrate Armadillo from a signaling pool.
• Identified a signaling pool of Armadillo that is functionally distinct from the junctional pool.

Conclusions:

• Wingless signaling can influence cell fate independently of direct modulation of cell adhesion.
• Armadillo plays a role in a signaling pathway separate from its function in adherens junctions.
• Cell adhesion and developmental signaling pathways are intricately linked but can be functionally dissociated.