Discovery and Characterization of Leucine-Rich Repeat-Containing G Protein-Coupled Receptors

  • Marie-Isabelle Garcia
  • Valeria Fernandez-Vallone
  • Gilbert Vassart
Part of the Methods in Pharmacology and Toxicology book series (MIPT)


Leucine-rich repeat-containing G protein-coupled receptors (LGRs) are type A rhodopsin-like GPCRs that include the glycoprotein pituitary hormone receptors for the thyroid-stimulating, follicle-stimulating, and luteinizing hormones (TSH, FSH, and LH); a pair of receptors for insulin-like peptides (LGR7, LGR8); and the LGR4, LGR5, and LGR6 receptors, which are the basis of this chapter. LGRs were initially identified as conceptual proteins extracted from DNA sequence databases, displaying sequence similarity with the glycoprotein hormone receptors. In 2007, LGR5 was identified as a marker of adult stem cells in several tissues, while still remaining an orphan GPCR with no known agonists. Since then, LGR4, LGR5, and LGR6 were shown to function as R-spondin receptors and controlling the Wnt pathway in a G protein-independent way. Whereas LGR4 deficiency causes developmental defects in many organs, fitting with its broad tissue expression pattern, LGR5 and LGR6 expression seems to be confined to stem cells, with only LGR5 knockout animals displaying a lethal malformation of the tongue (ankyloglossia). A consensus exists that LGR4 functions as a positive regulator of Wnt signaling, both in in vivo and in vitro Wnt reporter assays. For LGR5, whereas in vitro experiments show redundancy with LGR4 activity as a Wnt co-stimulator, arguments exist that it would inhibit rather than stimulate the Wnt pathway in vivo. The paradox of LGRs displaying many structural characteristics typical of rhodopsin-like GPCRs but showing G protein-independent R-spondin signaling activity leaves open the possibility that other agonists remain to be discovered.


Leucine-rich repeats GPCR 7TM receptors R-spondin Stem cells Wnt LGR4 LGR5 LGR6 



We want to thank Sylvie Claeysen, Fernando Medive, and Virginie Imbault, the successive postdocs and technician who worked for years on the frustrating subject of LGR deorphanization. Research is supported by the Fonds de la Recherche Scientifique-FNRS under Grant Nr 3.4504.11, the Walloon Region program “Cibles,” a grant from the Belgian Science Policy in the frame of the Interuniversity Attraction Poles Programme (P7/40), and the not-for-profit Association Recherche Biomédicale et Diagnostic asbl.


  1. 1.
    Vassart G, Pardo L, Costagliola S (2004) A molecular dissection of the glycoprotein hormone receptors. Trends Biochem Sci 29:119–126PubMedCrossRefGoogle Scholar
  2. 2.
    Kleinau G, Krause G (2009) Thyrotropin-and homologous glycoprotein hormone receptors: structural and functional aspects of extracellular signaling mechanisms. Endocr Rev 30:133–151PubMedCrossRefGoogle Scholar
  3. 3.
    Bathgate RA, Halls ML, van der Westhuizen ET et al (2013) Relaxin family peptides and their receptors. Physiol Rev 93:405–480PubMedCrossRefGoogle Scholar
  4. 4.
    Barker N, van Es JH, Kuipers J et al (2007) Identification of stem cells in small intestine and colon by marker gene Lgr5. Nature 449:1003–1007PubMedCrossRefGoogle Scholar
  5. 5.
    Snippert HJ, Haegebarth A, Kasper M et al (2010) Lgr6 marks stem cells in the hair follicle that generate all cell lineages of the skin. Science 327:1385–1389PubMedCrossRefGoogle Scholar
  6. 6.
    Parmentier M, Libert F, Maenhaut C et al (1989) Molecular cloning of the thyrotropin receptor. Science 246:1620–1622PubMedCrossRefGoogle Scholar
  7. 7.
    Loosfelt H, Misrahi M, Atger M et al (1989) Cloning and sequencing of porcine LH-hCG receptor cDNA: variants lacking transmembrane domain. Science 245:525–528PubMedCrossRefGoogle Scholar
  8. 8.
    McFarland KC, Sprengel R, Phillips HS et al (1989) Lutropin-choriogonadotropin receptor: an unusual member of the G protein-coupled receptor family. Science 245:494–499PubMedCrossRefGoogle Scholar
  9. 9.
    Minegishi T, Nakamura K, Takakura Y et al (1991) Cloning and sequencing of human FSH receptor cDNA. Biochem Biophys Res Commun 175:1125–1130PubMedCrossRefGoogle Scholar
  10. 10.
    Libert F, Parmentier M, Lefort A et al (1989) Selective amplification and cloning of four new members of the G protein-coupled receptor family. Science 244:569–572PubMedCrossRefGoogle Scholar
  11. 11.
    Nothacker HP, Grimmelikhuijzen CJ (1993) Molecular cloning of a novel, putative G protein-coupled receptor from sea anemones structurally related to members of the FSH, TSH, LH/CG receptor family from mammals. Biochem Biophys Res Commun 197:1062–1069PubMedCrossRefGoogle Scholar
  12. 12.
    Eriksen KK, Hauser F, Schiott M et al (2000) Molecular cloning, genomic organization, developmental regulation, and a knock-out mutant of a novel leu-rich repeats-containing G protein-coupled receptor (DLGR-2) from Drosophila melanogaster. Genome Res 10:924–938PubMedCrossRefGoogle Scholar
  13. 13.
    Hauser F, Nothacker HP, Grimmelikhuijzen CJ (1997) Molecular cloning, genomic organization, and developmental regulation of a novel receptor from Drosophila melanogaster structurally related to members of the thyroid-stimulating hormone, follicle-stimulating hormone, luteinizing hormone/choriogonadotropin receptor family from mammals. J Biol Chem 272:1002–1010PubMedCrossRefGoogle Scholar
  14. 14.
    Nishi S, Hsu SY, Zell K et al (2000) Characterization of two fly LGR (leucine-rich repeat-containing, G protein-coupled receptor) proteins homologous to vertebrate glycoprotein hormone receptors: constitutive activation of wild-type fly LGR1 but not LGR2 in transfected mammalian cells. Endocrinology 141:4081–4090PubMedGoogle Scholar
  15. 15.
    McDonald T, Wang R, Bailey W et al (1998) Identification and cloning of an orphan G protein-coupled receptor of the glycoprotein hormone receptor subfamily. Biochem Biophys Res Commun 247:266–270PubMedCrossRefGoogle Scholar
  16. 16.
    Hsu SY, Liang SG, Hsueh AJ (1998) Characterization of two LGR genes homologous to gonadotropin and thyrotropin receptors with extracellular leucine-rich repeats and a G protein-coupled, seven-transmembrane region. Mol Endocrinol 12:1830–1845PubMedGoogle Scholar
  17. 17.
    Hsu SY, Kudo M, Chen T et al (2000) The three subfamilies of leucine-rich repeat-containing G protein-coupled receptors (LGR): identification of LGR6 and LGR7 and the signaling mechanism for LGR7. Mol Endocrinol 14:1257–1271PubMedGoogle Scholar
  18. 18.
    Ballesteros JA, Weinstein H (1995) Integrated methods for the construction of three-dimensional models and computational probing of structure-function relations in G protein-coupled receptors. Methods Neurosci 25:366–428CrossRefGoogle Scholar
  19. 19.
    Van Hiel MB, Vandersmissen HP, Van LT et al (2012) An evolutionary comparison of leucine-rich repeat containing G protein-coupled receptors reveals a novel LGR subtype. Peptides 34:193–200PubMedCrossRefGoogle Scholar
  20. 20.
    Vitt UA, Hsu SY, Hsueh AJ (2001) Evolution and classification of cystine knot-containing hormones and related extracellular signaling molecules. Mol Endocrinol 15:681–694PubMedGoogle Scholar
  21. 21.
    Nakabayashi K, Matsumi H, Bhalla A et al (2002) Thyrostimulin, a heterodimer of two new human glycoprotein hormone subunits, activates the thyroid-stimulating hormone receptor. J Clin Invest 109:1445–1452PubMedCentralPubMedGoogle Scholar
  22. 22.
    Sudo S, Kuwabara Y, Park JI et al (2005) Heterodimeric fly glycoprotein hormone-alpha2 (GPA2) and glycoprotein hormone-beta5 (GPB5) activate fly leucine-rich repeat-containing G protein-coupled receptor-1 (DLGR1) and stimulation of human thyrotropin receptors by chimeric fly GPA2 and human GPB5. Endocrinology 146:3596–3604PubMedCrossRefGoogle Scholar
  23. 23.
    Baker JD, Truman JW (2002) Mutations in the Drosophila glycoprotein hormone receptor, rickets, eliminate neuropeptide-induced tanning and selectively block a stereotyped behavioral program. J Exp Biol 205:2555–2565PubMedGoogle Scholar
  24. 24.
    Mendive FM, Van Loy T, Claeysen S et al (2005) Drosophila molting neurohormone bursicon is a heterodimer and the natural agonist of the orphan receptor DLGR2. FEBS Lett 579:2171–2176PubMedCrossRefGoogle Scholar
  25. 25.
    Luo CW, Dewey EM, Sudo S et al (2005) Bursicon, the insect cuticle-hardening hormone, is a heterodimeric cystine knot protein that activates G protein-coupled receptor LGR2. Proc Natl Acad Sci U S A 102:2820–2825PubMedCentralPubMedCrossRefGoogle Scholar
  26. 26.
    Kleinau G, Neumann S, Gruters A et al (2013) Novel insights on thyroid stimulating hormone receptor signal transduction. Endocr Rev 34:691–724Google Scholar
  27. 27.
    Chen CR, Salazar LM, McLachlan SM et al (2012) The thyrotropin receptor hinge region as a surrogate ligand: identification of loci contributing to the coupling of thyrotropin binding and receptor activation. Endocrinology 153:5058–5067PubMedCrossRefGoogle Scholar
  28. 28.
    Gao Y, Kitagawa K, Shimada M et al (2006) Generation of a constitutively active mutant of human GPR48/LGR4, a G-protein-coupled receptor. Hokkaido Igaku Zasshi 81:101–105, 107, 109PubMedGoogle Scholar
  29. 29.
    Weng J, Luo J, Cheng X et al (2008) Deletion of G protein-coupled receptor 48 leads to ocular anterior segment dysgenesis (ASD) through down-regulation of Pitx2. Proc Natl Acad Sci U S A 105:6081–6086PubMedCentralPubMedCrossRefGoogle Scholar
  30. 30.
    Ruffner H, Sprunger J, Charlat O et al (2012) R-Spondin potentiates Wnt/β-catenin signaling through orphan receptors LGR4 and LGR5. PLoS One 7:e40976PubMedCentralPubMedCrossRefGoogle Scholar
  31. 31.
    Van Schoore G, Mendive F, Pochet R et al (2005) Expression pattern of the orphan receptor LGR4/GPR48 gene in the mouse. Histochem Cell Biol 124:35–50PubMedCrossRefGoogle Scholar
  32. 32.
    Mustata RC, Van LT, Lefort A et al (2011) LGR4 is required for Paneth cell differentiation and maintenance of intestinal stem cells ex vivo. EMBO Rep 12:558–564PubMedCentralPubMedCrossRefGoogle Scholar
  33. 33.
    Mazerbourg S, Bouley DM, Sudo S et al (2004) Leucine-rich repeat-containing, G protein-coupled receptor 4 null mice exhibit intrauterine growth retardation associated with embryonic and perinatal lethality. Mol Endocrinol 18:2241–2254PubMedCrossRefGoogle Scholar
  34. 34.
    Kato S, Mohri Y, Matsuo T et al (2007) Eye-open at birth phenotype with reduced keratinocyte motility in LGR4 null mice. FEBS Lett 581:4685–4690PubMedCrossRefGoogle Scholar
  35. 35.
    Wang Z, Jin C, Li H et al (2010) GPR48-induced keratinocyte proliferation occurs through HB-EGF mediated EGFR transactivation. FEBS Lett 584:4057–4062PubMedCrossRefGoogle Scholar
  36. 36.
    Mohri Y, Umezu T, Hidema S et al (2010) Reduced fertility with impairment of early-stage embryos observed in mice lacking LGR4 in epithelial tissues. Fertil Steril 94:2878–2881PubMedCrossRefGoogle Scholar
  37. 37.
    Mohri Y, Kato S, Umezawa A et al (2008) Impaired hair placode formation with reduced expression of hair follicle-related genes in mice lacking LGR4. Dev Dyn 237:2235–2242PubMedCrossRefGoogle Scholar
  38. 38.
    Mendive F, Laurent P, Van SG et al (2006) Defective postnatal development of the male reproductive tract in LGR4 knockout mice. Dev Biol 290:421–434PubMedCrossRefGoogle Scholar
  39. 39.
    Lambot MA, Mendive F, Laurent P et al (2009) Three-dimensional reconstruction of efferent ducts in wild-type and Lgr4 knock-out mice. Anat Rec 292:595–603CrossRefGoogle Scholar
  40. 40.
    Hoshii T, Takeo T, Nakagata N et al (2007) LGR4 regulates the postnatal development and integrity of male reproductive tracts in mice. Biol Reprod 76:303–313PubMedCrossRefGoogle Scholar
  41. 41.
    Li XY, Lu Y, Sun HY et al (2010) G protein-coupled receptor 48 upregulates estrogen receptor alpha expression via cAMP/PKA signaling in the male reproductive tract. Development 137:151–157PubMedCrossRefGoogle Scholar
  42. 42.
    Qian Y, Liu S, Guan Y et al (2013) LGR4-mediated Wnt/β-catenin signaling in peritubular myoid cells is essential for spermatogenesis. Development 140:1751–1761PubMedCrossRefGoogle Scholar
  43. 43.
    Kato S, Matsubara M, Matsuo T et al (2006) Leucine-rich repeat-containing G protein-coupled receptor-4 (LGR4, Gpr48) is essential for renal development in mice. Nephron Exp Nephrol 104:e63–e75PubMedCrossRefGoogle Scholar
  44. 44.
    Mohri Y, Oyama K, Akamatsu A et al (2011) LGR4-deficient mice showed premature differentiation of ureteric bud with reduced expression of Wnt effector Lef1 and Gata3. Dev Dyn 240:1626–1634PubMedCrossRefGoogle Scholar
  45. 45.
    Mohri Y, Oyama K, Sone M et al (2012) LGR4 is required for the cell survival of the peripheral mesenchyme at the embryonic stages of nephrogenesis. Biosci Biotechnol Biochem 76:888–891PubMedCrossRefGoogle Scholar
  46. 46.
    Wang J, Li X, Ke Y et al (2012) GPR48 increases mineralocorticoid receptor gene expression. J Am Soc Nephrol 23:281–293PubMedCrossRefGoogle Scholar
  47. 47.
    Yamashita R, Takegawa Y, Sakumoto M et al (2009) Defective development of the gall bladder and cystic duct in LGR4-hypomorphic mice. Dev Dyn 238:993–1000PubMedCrossRefGoogle Scholar
  48. 48.
    Luo J, Zhou W, Zhou X et al (2009) Regulation of bone formation and remodeling by G-protein-coupled receptor 48. Development 136:2747–2756PubMedCrossRefGoogle Scholar
  49. 49.
    Oyama K, Mohri Y, Sone M et al (2011) Conditional knockout of LGR4 leads to impaired ductal elongation and branching morphogenesis in mouse mammary glands. Sex Dev 5:205–212PubMedCrossRefGoogle Scholar
  50. 50.
    Song H, Luo J, Luo W et al (2008) Inactivation of G-protein-coupled receptor 48 (Gpr48/Lgr4) impairs definitive erythropoiesis at midgestation through down-regulation of the ATF4 signaling pathway. J Biol Chem 283:36687–36697PubMedCrossRefGoogle Scholar
  51. 51.
    Du B, Luo W, Li R et al (2013) LGR4/GPR48 negatively regulates TLR2/4-associated pattern recognition and innate immunity by targeting CD14 expression. J Biol Chem 288:15131–15141PubMedCrossRefGoogle Scholar
  52. 52.
    De Lau W, Barker N, Low TY et al (2011) LGR5 homologues associate with Wnt receptors and mediate R-spondin signaling. Nature 476:293–297PubMedCrossRefGoogle Scholar
  53. 53.
    Liu S, Qian Y, Li L et al (2013) Lgr4 gene deficiency increases susceptibility and severity of dextran sodium sulfate-induced inflammatory bowel disease in mice. J Biol Chem 288:8794–8803PubMedCrossRefGoogle Scholar
  54. 54.
    Styrkarsdottir U, Thorleifsson G, Sulem P et al (2013) Nonsense mutation in the LGR4 gene is associated with several human diseases and other traits. Nature 497:517–520PubMedCrossRefGoogle Scholar
  55. 55.
    Morita H, Mazerbourg S, Bouley DM et al (2004) Neonatal lethality of LGR5 null mice is associated with ankyloglossia and gastrointestinal distension. Mol Cell Biol 24:9736–9743PubMedCentralPubMedCrossRefGoogle Scholar
  56. 56.
    Garcia MI, Ghiani M, Lefort A et al (2009) LGR5 deficiency deregulates Wnt signaling and leads to precocious Paneth cell differentiation in the fetal intestine. Dev Biol 331:58–67PubMedCrossRefGoogle Scholar
  57. 57.
    Gao Y, Shan ZY, Wang H et al (2009) Inhibitory effect of shRNA targeting GPR48 on invasion and metastasis of human cervical carcinoma cell line HeLa. Ai Zheng 28:104–107PubMedGoogle Scholar
  58. 58.
    Huch M, Dorrell C, Boj SF et al (2013) In vitro expansion of single LGR5+ liver stem cells induced by Wnt-driven regeneration. Nature 494:247–250PubMedCentralPubMedCrossRefGoogle Scholar
  59. 59.
    Barker N, Rookmaaker MB, Kujala P et al (2012) LGR5(+ve) stem/progenitor cells contribute to nephron formation during kidney development. Cell Rep 2:540–552PubMedCrossRefGoogle Scholar
  60. 60.
    Chai R, Xia A, Wang T et al (2011) Dynamic expression of LGR5, a Wnt target gene, in the developing and mature mouse cochlea. J Assoc Res Otolaryngol 12:455–469PubMedCentralPubMedCrossRefGoogle Scholar
  61. 61.
    Vroegindeweij E, van Mourik I, Cupedo T et al (2013) Characterization of LGR5-positive epithelial cells in the murine thymus. Eur J Immunol 43:1243–1251PubMedCrossRefGoogle Scholar
  62. 62.
    Fukuma M, Tanese K, Effendi K et al (2013) Leucine-rich repeat-containing G protein-coupled receptor 5 regulates epithelial cell phenotype and survival of hepatocellular carcinoma cells. Exp Cell Res 319:113–121PubMedCrossRefGoogle Scholar
  63. 63.
    Walker F, Zhang HH, Odorizzi A et al (2011) LGR5 is a negative regulator of tumourigenicity, antagonizes Wnt signaling and regulates cell adhesion in colorectal cancer cell lines. PLoS One 6:e22733PubMedCentralPubMedCrossRefGoogle Scholar
  64. 64.
    Al-Kharusi MR, Smartt HJ, Greenhough A et al (2013) LGR5 promotes survival in human colorectal adenoma cells and is upregulated by PGE2: implications for targeting adenoma stem cells with NSAIDs. Carcinogenesis 34:1150–1157PubMedCrossRefGoogle Scholar
  65. 65.
    McClanahan T, Koseoglu S, Smith K et al (2006) Identification of overexpression of orphan G protein-coupled receptor GPR49 in human colon and ovarian primary tumors. Cancer Biol Ther 5:419–426PubMedCrossRefGoogle Scholar
  66. 66.
    Hirata-Tominaga K, Nakamura T, Okumura N et al (2013) Corneal endothelial cell fate is maintained by LGR5 via the regulation of hedgehog and Wnt pathway. Stem Cells 31:1396–1407PubMedCrossRefGoogle Scholar
  67. 67.
    Tanese K, Fukuma M, Yamada T et al (2008) G-protein-coupled receptor GPR49 is up-regulated in basal cell carcinoma and promotes cell proliferation and tumor formation. Am J Pathol 173:835–843PubMedCrossRefGoogle Scholar
  68. 68.
    Nakata S, Campos B, Bageritz J et al (2013) LGR5 is a marker of poor prognosis in glioblastoma and is required for survival of brain cancer stem-like cells. Brain Pathol 23:60–72PubMedCrossRefGoogle Scholar
  69. 69.
    Scannell CA, Pedersen EA, Mosher JT et al (2013) LGR5 is expressed by Ewing sarcoma and potentiates Wnt/β-catenin signaling. Front Oncol 3:81PubMedCentralPubMedCrossRefGoogle Scholar
  70. 70.
    Gao Y, Kitagawa K, Hiramatsu Y et al (2006) Up-regulation of GPR48 induced by down-regulation of p27Kip1 enhances carcinoma cell invasiveness and metastasis. Cancer Res 66:11623–11631PubMedCrossRefGoogle Scholar
  71. 71.
    Gong X, Carmon KS, Lin Q et al (2012) LGR6 is a high affinity receptor of R-spondins and potentially functions as a tumor suppressor. PLoS One 7:e37137PubMedCentralPubMedCrossRefGoogle Scholar
  72. 72.
    Niehrs C (2012) The complex world of WNT receptor signaling. Nat Rev Mol Cell Biol 13:767–779PubMedCrossRefGoogle Scholar
  73. 73.
    Gurney A (2009) Patent application number: 20090074782Google Scholar
  74. 74.
    Kim KA, Kakitani M, Zhao J et al (2005) Mitogenic influence of human R-spondin1 on the intestinal epithelium. Science 309:1256–1259PubMedCrossRefGoogle Scholar
  75. 75.
    Sato T, Vries RG, Snippert HJ et al (2009) Single LGR5 stem cells build crypt-villus structures in vitro without a mesenchymal niche. Nature 459:262–265PubMedCrossRefGoogle Scholar
  76. 76.
    Ootani A, Li X, Sangiorgi E et al (2009) Sustained in vitro intestinal epithelial culture within a Wnt-dependent stem cell niche. Nat Med 15:701–706PubMedCentralPubMedCrossRefGoogle Scholar
  77. 77.
    Wei Q, Yokota C, Semenov MV et al (2007) R-spondin1 is a high affinity ligand for LRP6 and induces LRP6 phosphorylation and β-catenin signaling. J Biol Chem 282:15903–15911PubMedCrossRefGoogle Scholar
  78. 78.
    Carmon KS, Gong X, Lin Q (2011) R-spondins function as ligands of the orphan receptors LGR4 and LGR5 to regulate Wnt/β-catenin signaling. Proc Natl Acad Sci U S A 108:11452–11457PubMedCentralPubMedCrossRefGoogle Scholar
  79. 79.
    Glinka A, Dolde C, Kirsch N et al (2011) LGR4 and LGR5 are R-spondin receptors mediating Wnt/beta-catenin and Wnt/PCP signaling. EMBO Rep 12:1055–1061PubMedCentralPubMedCrossRefGoogle Scholar
  80. 80.
    Wang D, Huang B, Zhang S et al (2013) Structural basis for R-spondin recognition by LGR4/5/6 receptors. Genes Dev 27:1339–1344PubMedCrossRefGoogle Scholar
  81. 81.
    Chen PH, Chen X, Lin Z et al (2013) The structural basis of R-spondin recognition by LGR5 and RNF43. Genes Dev 27:1345–1350PubMedCrossRefGoogle Scholar
  82. 82.
    MacDonald BT, He X (2012) A finger on the pulse of Wnt receptor signaling. Cell Res 22:1410–1412PubMedCrossRefGoogle Scholar
  83. 83.
    Hao HX, Xie Y, Zhang Y et al (2012) ZNRF3 promotes Wnt receptor turnover in an R-spondin-sensitive manner. Nature 485:195–200PubMedCrossRefGoogle Scholar
  84. 84.
    Koo BK, Spit M, Jordens I et al (2012) Tumour suppressor RNF43 is a stem-cell E3 ligase that induces endocytosis of Wnt receptors. Nature 488:665–669PubMedCrossRefGoogle Scholar
  85. 85.
    Fafilek B, Krausova M, Vojtechova M et al (2012) Troy, a tumor necrosis factor receptor family member, interacts with LGR5 to inhibit Wnt signaling in intestinal stem cells. Gastroenterology 144:381–391PubMedCrossRefGoogle Scholar
  86. 86.
    Parma P, Radi O, Vidal V et al (2006) R-spondin1 is essential in sex determination, skin differentiation and malignancy. Nat Genet 38:1304–1309PubMedCrossRefGoogle Scholar
  87. 87.
    Aoki M, Kiyonari H, Nakamura H et al (2008) R-spondin2 expression in the apical ectodermal ridge is essential for outgrowth and patterning in mouse limb development. Dev Growth Differ 50:85–95PubMedCrossRefGoogle Scholar
  88. 88.
    Aoki M, Mieda M, Ikeda T et al (2007) R-spondin3 is required for mouse placental development. Dev Biol 301:218–226PubMedCrossRefGoogle Scholar
  89. 89.
    Blaydon DC, Ishii Y, O’Toole EA et al (2006) The gene encoding R-spondin 4 (RSPO4), a secreted protein implicated in Wnt signaling, is mutated in inherited anonychia. Nat Genet 38:1245–1247PubMedCrossRefGoogle Scholar
  90. 90.
    Bergmann C, Senderek J, Anhuf D et al (2006) Mutations in the gene encoding the Wnt-signaling component R-spondin 4 (RSPO4) cause autosomal recessive anonychia. Am J Hum Genet 79:1105–1109PubMedCentralPubMedCrossRefGoogle Scholar
  91. 91.
    Deng C, Reddy P, Cheng Y et al (2013) Multi-functional norrin is a ligand for the LGR4 receptor. J Cell Sci 126:2060–2068PubMedCrossRefGoogle Scholar
  92. 92.
    Snyder JC, Rochelle LK, Lyerly HK et al (2013) Constitutive internalization of the leucine-rich G protein-coupled receptor-5 (LGR5) to the trans-Golgi network. J Biol Chem 288:10286–10297PubMedCrossRefGoogle Scholar
  93. 93.
    Dixon RA, Kobilka BK, Strader DJ et al (1986) Cloning of the gene and cDNA for mammalian β-adrenergic receptor and homology with rhodopsin. Nature 321:75–79PubMedCrossRefGoogle Scholar
  94. 94.
    Masu Y, Nakayama K, Tamaki H et al (1987) cDNA cloning of bovine substance-K receptor through oocyte expression system. Nature 329:836–838PubMedCrossRefGoogle Scholar
  95. 95.
    Kubo T, Fukuda K, Mikami A et al (1986) Cloning, sequencing and expression of complementary DNA encoding the muscarinic acetylcholine receptor. Nature 323:411–416PubMedCrossRefGoogle Scholar
  96. 96.
    Meunier JC, Mollereau C, Toll L et al (1995) Isolation and structure of the endogenous agonist of opioid receptor-like ORL1 receptor. Nature 377:532–535PubMedCrossRefGoogle Scholar
  97. 97.
    Reinscheid RK, Nothacker HP, Bourson A et al (1995) Orphanin FQ: a neuropeptide that activates an opioid-like G protein- coupled receptor. Science 270:792–794PubMedCrossRefGoogle Scholar
  98. 98.
    Zhang Y, Wang Z, Parks GS et al (2011) Novel neuropeptides as ligands of orphan G protein-coupled receptors. Curr Pharm Des 17:2626–2631PubMedCrossRefGoogle Scholar
  99. 99.
    Sakurai T, Amemiya A, Ishii M et al (1998) Orexins and orexin receptors: a family of hypothalamic neuropeptides and G protein-coupled receptors that regulate feeding behavior. Cell 92:573–585PubMedCrossRefGoogle Scholar
  100. 100.
    Samson M, Labbe O, Mollereau C et al (1996) Molecular cloning and functional expression of a new human CC-chemokine receptor gene. Biochemistry 35:3362–3367PubMedCrossRefGoogle Scholar
  101. 101.
    Wittamer V, Franssen JD, Vulcano M et al (2003) Specific recruitment of antigen-presenting cells by chemerin, a novel processed ligand from human inflammatory fluids. J Exp Med 198:977–985PubMedCentralPubMedCrossRefGoogle Scholar
  102. 102.
    Molenaar M, van de Wetering M, Oosterwegel M et al (1996) XTcf-3 transcription factor mediates beta-catenin-induced axis formation in Xenopus embryos. Cell 86:391–399PubMedCrossRefGoogle Scholar
  103. 103.
    Molenaar M, Roose J, Peterson J et al (1998) Differential expression of the HMG box transcription factors XTcf-3 and XLef-1 during early Xenopus development. Mech Dev 75: 151–154PubMedCrossRefGoogle Scholar
  104. 104.
    Kazanskaya O, Glinka A, del Barco Barrantes I et al (2004) R-Spondin2 is a secreted activator of Wnt/β-catenin signaling and is required for Xenopus myogenesis. Dev Cell 7:525–534PubMedCrossRefGoogle Scholar
  105. 105.
    Lakso M, Sauer B, Mosinger B et al (1992) Targeted oncogene activation by site-specific recombination in transgenic mice. Proc Natl Acad Sci U S A 89:6232–6236PubMedCentralPubMedCrossRefGoogle Scholar
  106. 106.
    Mao X, Fujiwara Y, Chapdelaine A et al (2001) Activation of EGFP expression by Cre-mediated excision in a new ROSA26 reporter mouse strain. Blood 97:324–326PubMedCrossRefGoogle Scholar
  107. 107.
    Feil R, Brocard J, Mascrez B et al (1996) Ligand-activated site-specific recombination in mice. Proc Natl Acad Sci U S A 93:10887–10890PubMedCentralPubMedCrossRefGoogle Scholar
  108. 108.
    Indra AK, Warot X, Brocard J et al (1999) Temporally-controlled site-specific mutagenesis in the basal layer of the epidermis: comparison of the recombinase activity of the tamoxifen-inducible Cre-ER(T) and Cre-ER(T2) recombinases. Nucleic Acids Res 27:4324–4327PubMedCentralPubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  • Marie-Isabelle Garcia
    • 1
  • Valeria Fernandez-Vallone
    • 1
  • Gilbert Vassart
    • 1
  1. 1.Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, Faculty of MedicineUniversité Libre de BruxellesBrusselsBelgium

Personalised recommendations