Anti-GPR48 (C-terminal) polyclonal antibody

R-spondin proteins are adult stem cell growth factors capable of stimulating gut development by activating LGR4, 5, and 6 receptors to promote Wnt signaling. Although multiple Wnt ligands and cognate Frizzled receptors are expressed in the ovary, their physiological roles are unclear. Based on bioinformatic and in situ hybridization analyses, we demonstrated the exclusive expression of R-spondin2 in oocytes of ovarian follicles. In cultured somatic cells from preantral follicles, R-spondin2 treatment (ED50:3 ng/ml) synergized with Wnt3a to stimulate Wnt signaling. In cultured ovarian explants from prepubertal mice containing preantral follicles, treatment with R-spondin2, similar to follicle stimulating hormone, promoted the development of primary follicles to the secondary stage. In vivo administration of an R-spondin agonist stimulated the development of primary follicles to the antral stage in both immature mice and gonadotropin releasing hormone antagonist-treated adult mice. Subsequent treatment with gonadotropins allowed the generation of mature oocytes capable of undergoing early embryonic development and successful pregnancy. Furthermore, R-spondin agonist treatment of immune-deficient mice grafted with human cortical fragments stimulated the development of primary follicles to the secondary stage. Thus, oocyte-derived R-spondin2 is a paracrine factor essential for primary follicle development, and R-spondin agonists could provide a new treatment regimen for infertile women with low responses to the traditional gonadotropin therapy.

Leucine-rich repeat-containing G-protein-coupled receptor 4 (LGR4) is produced in a broad spectrum of mouse embryonic and adult tissues and its deficiency results in embryonal or perinatal lethality. The LGR4 function was mainly related to its potentiation of canonical Wnt signaling; however, several recent studies associate LGR4 with additional signaling pathways. To obtain a suitable tool for studying the signaling properties of Lgr4, we generated a tagged variant of the Lgr4 receptor using gene targeting in the mouse oocyte. The modified Lgr4 allele expresses the Lgr4 protein fused with a triple hemagglutinin (3HA) tag located at the extracellular part of the protein. The allele is fully functional, enabling tracking of Lgr4 expression in the mouse tissues. We also show that via surface labeling, the 3HA tag allows direct isolation and analysis of living Lgr4-positive cells obtained from the small intestinal crypts. Finally, the HA tag-specific antibody can be employed to characterize the biochemical features of Lgr4 and to identify possible biding partners of the protein in cells derived from various mouse tissues.