EFN-4/Ephrin converges with SAX-3/Robo, UNC-6/Netrin, and Heparan Sulfate Proteoglycan signaling to control MAB-5/Hox-dependent posterior Q neuroblast migration in Caenorhabditis elegans.

EFN-4/Ephrin, along with SAX-3/Robo, UNC-6/Netrin, and HSPGs, forms an extracellular signaling complex essential for posterior Q neuroblast migration in C. elegans, with a key role in PQR neuron placement.

• Why it matters: Understanding the molecular pathways downstream of Hox genes like MAB-5 is crucial for revealing how nervous system development is precisely controlled, addressing a significant gap in developmental genetics.
• What they did: The study screened known signaling mutants and found that mutations in SAX-3/Robo, UNC-6/Netrin, and HSPGs caused weak third-stage PQR migration defects, with double mutants indicating these molecules converge on a common pathway, supported by in vitro interaction data.
• The result: This work suggests that MAB-5/Hox promotes EFN-4/Ephrin expression, which initiates the formation of a large extracellular signaling complex necessary for posterior neuroblast migration, advancing understanding of neural development mechanisms.