title: A naturally occurring Lgr4 splice variant encodes a soluble antagonist useful for demonstrating the gonadal roles of Lgr4 in mammals.
abstract: Leucine-rich repeat containing G protein-coupled receptor 4 (LGR4) promotes the Wnt signaling through interaction with R-spondins or norrin. Using PCR amplification from rat ovarian cDNAs, we identified a naturally occurring Lgr4 splice variant encoding only the ectodomain of Lgr4, which was named Lgr4-ED. Lgr4-ED can be detected as a secreted protein in the extracts from rodent and bovine postnatal gonads, suggesting conservation of Lgr4-ED in mammals. Recombinant Lgr4-ED purified from the conditioned media of transfected 293T cells was found to dose-dependently inhibit the LGR4-mediated Wnt signaling induced by RSPO2 or norrin, suggesting that it is capable of ligand absorption and could have a potential role as an antagonist. Intraperitoneal injection of purified recombinant Lgr4-ED into newborn mice was found to significantly decrease the testicular expression of estrogen receptor alpha and aquaporin 1, which is similar to the phenotype found in Lgr4-null mice. Administration of recombinant Lgr4-ED to superovulated female rats can also decrease the expression of estrogen receptor alpha, aquaporin 1, LH receptor and other key steroidogenic genes as well as bring about the suppression of progesterone production. Thus, these findings suggest that endogenously expressed Lgr4-ED may act as an antagonist molecule and help to fine-tune the R-spondin/norrin-mediated Lgr4-Wnt signaling during gonadal development.
authors.affiliation: Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Pei-Jen
authors.initials: PJ
authors.lastname: Hsu
authors.affiliation: Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Fang-Ju
authors.initials: FJ
authors.lastname: Wu
authors.affiliation: Division of Reproductive and Stem Cell Biology, Department of Obstetrics and Gynecology, Stanford University School of Medicine, Stanford, California, United States of America.
authors.forename: Masataka
authors.initials: M
authors.lastname: Kudo
authors.affiliation: Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Chih-Lun
authors.initials: CL
authors.lastname: Hsiao
authors.affiliation: Division of Reproductive and Stem Cell Biology, Department of Obstetrics and Gynecology, Stanford University School of Medicine, Stanford, California, United States of America.
authors.forename: Aaron J W
authors.initials: AJ
authors.lastname: Hsueh
authors.affiliation: Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Ching-Wei
authors.initials: CW
authors.lastname: Luo
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D051398:Aquaporin 1 / Q000235:genetics / Q000378:metabolism; D002417:Cattle; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism; D005136:Eye Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D010053:Ovary / Q000254:growth & development / Q000378:metabolism*; D010060:Ovulation; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000235:genetics* / Q000378:metabolism; D011974:Receptors, LH / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction; D013737:Testis / Q000254:growth & development / Q000378:metabolism*; D019699:Thrombospondins / Q000235:genetics* / Q000378:metabolism; D000098907:R-Spondins
chemical_list: D051398:Aquaporin 1; D047628:Estrogen Receptor alpha; D005136:Eye Proteins; D009419:Nerve Tissue Proteins; D043562:Receptors, G-Protein-Coupled; D011974:Receptors, LH; D019699:Thrombospondins; C496021:Aqp1 protein, mouse; C496200:LGR4 protein, mouse; C489916:Ndph protein, mouse; C518904:RSPO2 protein, mouse; D000098907:R-Spondins