Wnt and EGF pathways act together to induce C. elegans male hook development

Area of Science:

• Developmental Biology
• Evolutionary Developmental Biology
• Molecular Genetics

Background:

• Comparative studies of vulva development offer insights into patterning network evolution.
• Molecular genetic details of vulva development are primarily known in C. elegans and P. pacificus.
• The C. elegans male hook competence group (HCG) shares developmental origins with vulval precursor cells (VPCs).

Purpose of the Study:

• To investigate the evolution of patterning networks by studying C. elegans HCG development.
• To elucidate the roles of Wnt and EGF signaling in HCG cell fate specification.
• To compare HCG and VPC fate determination mechanisms.

Main Methods:

• Analysis of HCG cell fate adoption (1°, 2°, 3° fates).
• Investigation of LIN-12/Notch mediation in 2° HCG fate specification.
• Examination of Wnt signaling (LIN-17) and EGF signaling roles in HCG fate determination.
• Analysis of gene expression patterns (lin-17, bar-1/beta-catenin) and protein localization (BAR-1-GFP).

Main Results:

• 2° HCG specification requires a neighboring 1° fate cell.
• Wnt signaling via LIN-17 is crucial for specifying 1° and 2° HCG fates.
• EGF signaling is required for 1° HCG fate only when Wnt signaling is compromised; its activation can lead to ectopic hook development.
• Wnt signaling is also essential for the execution of 1° and 2° HCG lineages.
• lin-17 and bar-1 expression and BAR-1-GFP localization correlate with 1° HCG fate determination.

Conclusions:

• Wnt signaling plays a more dominant role than EGF signaling in HCG fate specification.
• The overall logic of fate specification in HCGs (EGF/Wnt inducing 1°, LIN-12/NOTCH inducing 2°) is similar to VPCs.
• Wnt signaling is critical for both HCG fate determination and lineage execution, highlighting its conserved importance in related developmental contexts.