Essential for the first active step of germ cell migration: transepithelial migration of germ cells through the posterior midgut (PMG) epithelium. In embryos, expression is seen at highest levels in the cuprophilic cells and at lower levels in the amnioserosa, developing CNS, cardiac mesoderm primordium and midline glia. Expressed both maternally and zygotically throughout embryo to adult stages. Most germ cells do not exit the posterior midgut (PMG) and remain clumped together within the midgut pocket. The few germ cells that do leave the midgut early migrate normally to the gonad. Overexpression of the Tre1 gene restores the taste sensitivity to trehalose in a Tre1 mutant (PubMed:10884225). This experiment cannot be explained given that other authors demonstrate that trehalose sensitivity maps to the adjacent gene, Gr5a (PubMed:14691551). Belongs to the G-protein coupled receptor 1 family.