Two functionally distinct Axin-like proteins regulate canonical Wnt signaling in C. elegans

Area of Science:

• Developmental Biology
• Molecular Biology
• Genetics

Background:

• Axin is a key negative regulator of the Wnt signaling pathway, interacting with APC and GSK3beta to control beta-catenin levels.
• In Caenorhabditis elegans, the Axin ortholog PRY-1 negatively regulates Wnt signaling, but its null phenotype is not fully penetrant, suggesting other factors are involved.

Purpose of the Study:

• To clone and functionally characterize a second Axin-like protein in C. elegans.
• To investigate the functional redundancy and specificity of Axin orthologs (PRY-1 and AXL-1) in Wnt signaling.

Main Methods:

• Cloning of the AXL-1 gene.
• Functional analysis of AXL-1 in C. elegans developmental processes.
• Comparative analysis of AXL-1 and PRY-1 functions.

Main Results:

• A second Axin-like protein, AXL-1, was identified and shown to be a functional Axin ortholog despite sequence divergence.
• AXL-1 functions redundantly with PRY-1 in regulating Wnt signaling in the vulva and Q neuroblast lineage.
• AXL-1 exhibits independent roles in Wnt signaling during excretory cell development, unlike vertebrate Axin and Conductin.

Conclusions:

• Axin function in C. elegans is divided between two distinct orthologs, PRY-1 and AXL-1.
• These two Axin orthologs possess specific, non-equivalent functions in the negative regulation of canonical Wnt signaling during development.