title: CXC chemokine receptor 7 (CXCR7) affects the migration of GnRH neurons by regulating CXCL12 availability.
abstract: Gonadotropin-releasing hormone (GnRH) neurons are neuroendocrine cells, located in the hypothalamus, that play an essential role in mammalian reproduction. These neurons originate in the nasal placode and migrate during embryonic development, in association with olfactory/vomeronasal nerves, first in the nose, then through the cribriform plate to enter the forebrain, before settling in the hypothalamus. One of the molecules required for their early migration in the nose is the chemokine CXCL12, which is expressed in the embryonic nasal mesenchyme in an increasing ventral to dorsal gradient, presumably guiding GnRH neurons toward the forebrain. Mice lacking CXCR4, the receptor for CXCL12, exhibit defective GnRH cell movement and a significant reduction in their number, suggesting that CXCL12/CXCR4 signaling is important in the migration and survival of these neurons. Here, we investigated the role of the more recently identified second CXCL12 receptor, CXCR7, in GnRH neuron development. We demonstrate that CXCR7 is expressed along the migratory path of GnRH neurons in the nasal cavity and, although not expressed by GnRH neurons, it affects their migration as indicated by the ectopic accumulation of these cells in the nasal compartment in CXCR7(-/-) mice. Absence of CXCR7 caused abnormal accumulation of CXCL12-RFP at CXCR4-positive sites in the nasal area of CXCL12-RFP-transgenic mice and excessive CXCL12-dependent intracellular clustering of CXCR4 in GnRH neurons, suggesting internalization. These findings imply that CXCR7 regulates CXCL12 availability by acting as a scavenger along the migratory path of GnRH neurons and, thus, influences the migration of these cells in a noncell-autonomous manner.
authors.affiliation: Department of Cell and Developmental Biology, University College London, WC1E 6BT, United Kingdom, Department of Pharmacology and Toxicology, University Hospital Jena, Friedrich-Schiller University, 07747 Jena, Germany, and Department of Immunology, Monash University, Alfred Medical Research and Education Precinct (AMREP), Melbourne, Victoria 3000, Australia.
authors.forename: Fani
authors.initials: F
authors.lastname: Memi
authors.forename: Philipp
authors.initials: P
authors.lastname: Abe
authors.forename: Anna
authors.initials: A
authors.lastname: Cariboni
authors.forename: Fabienne
authors.initials: F
authors.lastname: MacKay
authors.forename: John G
authors.initials: JG
authors.lastname: Parnavelas
authors.forename: Ralf
authors.initials: R
authors.lastname: Stumm
mesh_terms: D000818:Animals; D002465:Cell Movement / Q000502:physiology*; D054377:Chemokine CXCL12 / Q000096:biosynthesis / Q000235:genetics*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009474:Neurons / Q000166:cytology* / Q000502:physiology*; D011247:Pregnancy; D054387:Receptors, CXCR / Q000172:deficiency / Q000235:genetics* / Q000502:physiology*; D019718:Receptors, CXCR4 / Q000172:deficiency / Q000235:genetics
chemical_list: C501896:ACKR3 protein, human; C527276:CXCR4 protein, human; D054377:Chemokine CXCL12; C501897:Cmkor1 protein, mouse; C515256:Cxcl12 protein, mouse; D054387:Receptors, CXCR; D019718:Receptors, CXCR4; D007987:Gonadotropin-Releasing Hormone