Reevaluating the relationship between EGL-43 (EVI1) and LIN-12 (Notch) during C. elegans anchor cell invasion.

Area of Science:

• Developmental Biology
• Cell Biology
• Genetics

Background:

• Anchor cell (AC) invasion is crucial for Caenorhabditis elegans reproductive tract development, connecting uterine and vulval tissues.
• Transcription factors like EGL-43, HLH-2, and NHR-67 maintain the AC's post-mitotic state, essential for invasion.
• Previous models suggested EGL-43 represses LIN-12 (Notch) to prevent AC proliferation, implying Notch signaling promotes AC mitogenesis.

Purpose of the Study:

• To reexamine the relationship between EGL-43 and LIN-12 in regulating AC proliferation.
• To develop and validate a novel heterologous co-expression system (AIDHB) for studying gene function and cell-cycle dynamics.

Main Methods:

• Developed the AIDHB system, combining the auxin-inducible degron (AID) system with a live cell-cycle sensor (human DNA helicase B, DHB).
• Validated AIDHB using AID-tagged GFP and tested it with AID-tagged alleles of egl-43 and lin-12.
• Utilized AIDHB with RNA interference (RNAi) to simultaneously deplete LIN-12 and EGL-43.

Main Results:

• Auxin-induced degradation of EGL-43 or LIN-12 led to expected AC phenotypes.
• Co-depletion of LIN-12 and EGL-43 revealed that LIN-12 is not required for AC proliferation upon EGL-43 loss.
• This finding challenges the model where EGL-43-mediated repression of LIN-12 is essential for preventing AC proliferation.

Conclusions:

• The study demonstrates that LIN-12 signaling is dispensable for EGL-43-dependent AC proliferation.
• The developed AIDHB system provides a robust tool for investigating gene function and cell-cycle regulation in vivo.
• These findings necessitate a revision of the current model of AC proliferation control during reproductive tract development.