Distinct beta-catenins mediate adhesion and signalling functions in C. elegans

Area of Science:

• Molecular Biology
• Developmental Biology
• Genetics

Background:

• Beta-catenin proteins are crucial for Wnt signaling and cell adhesion in vertebrates and flies.
• In C. elegans, three beta-catenin homologues (WRM-1, BAR-1, HMP-2) exist, with WRM-1 and POP-1 previously implicated in Wnt signaling.
• The precise roles and interactions of these homologues in C. elegans remained unclear.

Purpose of the Study:

• To elucidate the specific functions of C. elegans beta-catenin homologues in Wnt signaling and cell adhesion.
• To determine which beta-catenin homologue directly interacts with the Tcf homologue POP-1.
• To clarify the mechanism of Wnt pathway activation and gene expression in C. elegans.

Main Methods:

• Co-immunoprecipitation assays to test protein interactions between beta-catenin homologues and POP-1.
• Analysis of gene expression, specifically the Hox gene mab-5, in response to BAR-1/POP-1 complex formation.
• Investigating the interaction between HMP-2 and the C. elegans cadherin HMR-1.

Main Results:

• BAR-1 was identified as the sole beta-catenin homologue that directly interacts with POP-1.
• The BAR-1/POP-1 complex functions as a bipartite transcription factor, activating Wnt target genes like mab-5.
• HMP-2 was found to be the only beta-catenin homologue interacting with the C. elegans cadherin HMR-1.

Conclusions:

• A canonical Wnt signaling pathway operates in C. elegans.
• The functions of beta-catenins in cell adhesion and Wnt signaling are segregated into distinct proteins in C. elegans.
• BAR-1 mediates Wnt signaling, while HMP-2 is responsible for cell adhesion.