DNA sequences encoding the murine ortholog of the human P2Y12 receptor were cloned. The human and mouse P2Y12 receptors were expressed in a yeast cell-based GPCR expression technology containing, chimeric yeast Galpha protein (Gpa1) constructs in which the 5 C-terminal amino acids were identical to corresponding sequences front mammalian Galphai/o proteins. LacZ reporter gene assays of agonist-induced activation of the G protein-coupled mating signal transduction pathway revealed murine P2Y12 functional pharmacological properties that closely resembled those exhibited by the human P2Y12 receptor. In NIH3T3 cells, the mouse P2Y12 stimulated calcium uptake monitored in FLIPR via coupling to a Galphaq/i3 chimeric protein. Murine P2Y12 mRNA was expressed at high levels in the brain and at lower levels in a variety of peripheral tissues. In situ hybridization analysis indicated glia-specific expression within the brain. (C) 2004 Elsevier Inc. All rights reserved.