Tre1 multifunctional domain model. Germ cells express both Wunen (green) and Tre1 (orange). We hypothesize that a still unknown phospholipid (PL) acts as a ligand for Tre1. This putative Tre1 ligand is distributed along gradients generated in somatic tissues via Wunen-dependent PL hydrolysis and lipid uptake. Germ cells move toward higher concentrations of the PL and, as a consequence, away from Wunen-expressing tissues. Expression of Wunen in the neuroectoderm leads to bilateral sorting of germ cells away from the ventral midline (top). Activation of the receptor and bilateral sorting requires the NRY domain and is mediated by Gαo signaling. The NPIIY domain of Tre1 acts via Rho1, possibly mediated by receptor dimerization. This leads to cell polarization and redistribution of Rho1 and E-cadherin to the germ cell tail. Wunen expression in germ cells promotes germ cell survival. This Wunen-dependent survival function is somehow counteracted by Tre1. This function of Tre1 is mediated by the NRY domain but is independent of Gαo signaling.