Characterization of lpa(2) (Edg4) and lpa(1)/lpa(2) (Edg2/Edg4) lysophosphatidic acid receptor knockout mice: signaling deficits without obvious phenotypic abnormality attributable to lpa(2)

Mol Cell Biol. 2002 Oct;22(19):6921-9. doi: 10.1128/MCB.22.19.6921-6929.2002.


Lysophosphatidic acid (LPA), a bioactive lipid produced by several cell types including postmitotic 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. We have previously shown that deletion of lpa(1) in mice results in craniofacial dysmorphism, semilethality due to defective suckling behavior, and generation of a small fraction of pups with frontal hematoma. To further investigate the role of these receptors and LPA signaling in the organism, we deleted lpa(2) in mice. Homozygous knockout (lpa(2)((-/-))) mice were born at the expected frequency and displayed no obvious phenotypic abnormalities. Intercrosses allowed generation of lpa(1)((-/-)) lpa(2)((-/-)) double knockout mice, which displayed no additional phenotypic abnormalities relative to lpa(1)((-/-)) mice except for an increased incidence of perinatal frontal hematoma. Histological analyses of lpa(1)((-/-)) lpa(2)((-/-)) embryonic cerebral cortices did not reveal obvious differences in the proliferating cell population. However, many LPA-induced responses, including phospholipase C activation, Ca(2+) 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. Except for adenylyl cyclase activation [which was nearly abolished in lpa(1)((-/-)) fibroblasts], these responses were only partially affected in lpa(1)((-/-)) and lpa(2)((-/-)) fibroblasts. Thus, although LPA(2) is not essential for normal mouse development, it does act redundantly with LPA(1) to mediate most LPA responses in fibroblasts.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenylyl Cyclases / metabolism
  • Animals
  • Calcium / metabolism
  • Cell Division / drug effects
  • Cells, Cultured
  • Cerebral Cortex / cytology
  • Cerebral Cortex / embryology
  • Crosses, Genetic
  • Enzyme Activation / drug effects
  • Enzyme Activation / physiology
  • Female
  • Fibroblasts / cytology
  • Fibroblasts / drug effects
  • Fibroblasts / metabolism
  • Gene Targeting
  • Hematoma / genetics
  • Homozygote
  • Lysophospholipids / pharmacology
  • Male
  • Mice
  • Mice, Knockout
  • Phenotype
  • Protein Serine-Threonine Kinases*
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-akt
  • Receptors, Cell Surface / deficiency*
  • Receptors, Cell Surface / genetics
  • Receptors, G-Protein-Coupled*
  • Receptors, Lysophosphatidic Acid
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*
  • Stress Fibers / metabolism
  • Type C Phospholipases / metabolism


  • Lysophospholipids
  • Proto-Oncogene Proteins
  • Receptors, Cell Surface
  • Receptors, G-Protein-Coupled
  • Receptors, Lysophosphatidic Acid
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Type C Phospholipases
  • Adenylyl Cyclases
  • Calcium