Pros1 is the ligand for the pathway, which signals via the receptor tyrosine kinase Axl. Signaling via Axl has been implicated in conferring cells with migratory properties in different biological context, including EMT-mediated cancer invasion46–48, and directional migration has been recently shown to be crucial for normal dermal condensate formation upon hair follicle morphogenesis42. The gene discussed is NTRK1; the disease is cancer.