Lysophosphatidic acid (LPA), a bioactive lipid produced by several cell types including pos™itotic neurons and activated platelets, is thought to be involved in various biological processes, including brain development. Three cognate G-protein coupled receptors encoded by lpa(1)/lp(A1)/Edg-2/Gpcr26, lpa(2)/lp(A2)/Edg-4, and lpa(3)/lp(A3)/Edg-7 mediate the cellular effects of LPA. However, many LPA-induced responses, including phospholipase C activation, Ca2+ mobilization, adenylyl cyclase activation, proliferation, JNK activation, AKT activation, and stress fiber formation, were absent or severely reduced in embryonic fibroblasts derived from lpa(1)(-/-) lpa(2)(-/-) mice. The lysophosphatidic acid receptor LPA2 or endothelial differentiation, G-protein coupled receptor 4(EDG-4) is expressed most abundantly in testes and peripheral blood leukocytes. It is reported to be a distinctive functional marker for ovarian carcinoma.