title: Loss of nectin-2 at Sertoli-spermatid junctions leads to male infertility and correlates with severe spermatozoan head and midpiece malformation, impaired binding to the zona pellucida, and oocyte penetration.
abstract: The members of the nectin/CD155 gene family represent a growing class of novel cell adhesion molecules of the immunoglobulin superfamily. In the present study, we describe the generation of a mouse line lacking a functional nectin-2 gene (nectin-2LacZ/LacZ) and analyze the resulting male-specific infertility phenotype. Although nectin-2LacZ/LacZ males produced normal amounts of motile spermatozoa, scanning electron microscopy revealed severe malformations of the spermatozoan head and midpiece. Besides a 4-fold reduction in migration of nectin-2LacZ/LacZ spermatozoa to the oviducts, in vitro binding to zona-intact mouse oocytes was reduced 6-fold. On the other hand, nectin-2LacZ/LacZ spermatozoa bound to zona-free hamster oocytes at near-wild type levels but, remarkably, failed to penetrate. In addition to the previously reported expression of nectin-2 and nectin-3 at Sertoli-spermatid junctions and of nectin-2 at inter-Sertoli cell junctions, we also found nectin-2 to localize at apical cell-cell junctions of the epididymal epithelium. Expression analysis of a LacZ knockin gene into the defunct nectin-2 gene in nectin-2LacZ/LacZ mice provided additional support for our earlier conjecture that in normal testis, nectin-2 is produced exclusively by Sertoli cells. Finally, we found Sertoli-spermatid junctions in nectin-2LacZ/LacZ mice to be virtually devoid of the actin-bundling protein espin, suggesting that ectoplasmic specializations fail to form in the absence of nectin-2. Our functional analyses indicate that the infertility phenotype of nectin-2-deficient male mice is caused by a combination of reduced migration to the oviduct, spermatozoa-zona binding, and sperm-oocyte fusion. We corroborate our previous description of a heterotypic adhesion complex between Sertoli cells and elongated spermatids that is maintained by nectin-2 and nectin-3, respectively.
authors.affiliation: Department of Molecular Genetics, State University of New York at Stony Brook, New York 11794, USA.
authors.forename: Steffen
authors.initials: S
authors.lastname: Mueller
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Rosenquist
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Takai
authors.forename: Richard A
authors.initials: RA
authors.lastname: Bronson
authors.forename: Eckard
authors.initials: E
authors.lastname: Wimmer
mesh_terms: D000818:Animals; D015815:Cell Adhesion Molecules / Q000235:genetics* / Q000378:metabolism; D004822:Epididymis / Q000378:metabolism; D005260:Female; D005818:Genetic Engineering / Q000379:methods; D007248:Infertility, Male / Q000235:genetics* / Q000473:pathology; D007365:Intercellular Junctions / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000378:metabolism; D000075983:Nectins; D009865:Oocytes / Q000378:metabolism; D012708:Sertoli Cells / Q000166:cytology* / Q000378:metabolism; D013081:Sperm Motility / Q000235:genetics; D013084:Sperm-Ovum Interactions / Q000502:physiology*; D013087:Spermatids / Q000166:cytology*; D013094:Spermatozoa / Q000378:metabolism / Q000473:pathology*; D015044:Zona Pellucida / Q000378:metabolism
chemical_list: D015815:Cell Adhesion Molecules; D008840:Microfilament Proteins; C000619017:Nectin3 protein, mouse; D000075983:Nectins; C104108:espin protein, mouse