title: Reproductive physiology of a humanized GnRH receptor mouse model: application in evaluation of human-specific analogs.
abstract: The human GnRH receptor (GNRHR1) has a specific set of properties with physiological and pharmacological influences not appropriately modeled in laboratory animals or cell-based systems. To address this deficiency, we have generated human GNRHR1 knock-in mice and described their reproductive phenotype. Measurement of pituitary GNRHR1 transcripts from homozygous human GNRHR1 knock-in (ki/ki) mice revealed a severe reduction (7- to 8-fold) compared with the mouse Gnrhr1 in wild-type mice. ¹²⁵I-GnRH binding assays on pituitary membrane fractions corroborated reduced human GNRHR1 protein expression in ki/ki mice, as occurs with transfection of human GNRHR1 in cell lines. Female homozygous knock-in mice displayed normal pubertal onset, indicating that a large reduction in GNRHR1 expression is sufficient for this process. However, ki/ki females exhibited periods of prolonged estrous and/or metestrous and reduced fertility. No impairment was found in reproductive maturity or adult fertility in male ki/ki mice. Interestingly, the serum LH response to GnRH challenge was reduced in both knock-in males and females, indicating a reduced GNRHR1 signaling capacity. Small molecules targeting human GPCRs usually have poor activities at homologous rodent receptors, thus limiting their use in preclinical development. Therefore, we tested a human-specific GnRH1 antagonist, NBI-42902, in our mouse model and demonstrated abrogation of a GnRH1-induced serum LH rise in ki/ki mice and an absence of effect in littermates expressing the wild-type murine receptor. This novel model provides the opportunity to study the human receptor in vivo and for screening the activity of human-specific GnRH analogs.
authors: Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom.
authors: Javier A
authors: JA
authors: Tello
authors: Trudy
authors: T
authors: Kohout
authors: Rafael
authors: R
authors: Pineda
authors: Richard A
authors: RA
authors: Maki
authors: R
authors: R
authors: Scott Struthers
authors: Robert P
authors: RP
authors: Millar
mesh_terms: D000818:Animals; D030762:Estrous Cycle / Q000502:physiology*; D025461:Feedback, Physiological / Q000187:drug effects / Q000502:physiology; D005260:Female; D005298:Fertility / Q000502:physiology*; D055879:Gene Knock-In Techniques; D006801:Humans; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D023421:Models, Animal; D010641:Phenotype; D010902:Pituitary Gland / Q000502:physiology; D011247:Pregnancy; D011966:Receptors, LHRH / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000502:physiology*; D012098:Reproduction / Q000502:physiology*; D012741:Sexual Maturation / Q000502:physiology; D013737:Testis / Q000254:growth & development / Q000502:physiology; D013941:Thymine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: C498569:3-(2-amino-2-phenylethyl)-1-(2,6-difluorobenzyl)-5-(2-fluoro-3-methoxyphenyl)-6-methylpyrimidin-2,4-dione; D011966:Receptors, LHRH; D013941:Thymine
keywords: follicle-stimulating hormone; gonadotropin-releasing hormone; luteinizing hormone