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

• Published in: Biology of reproduction 2003-10, Vol.69 (4), p.1330-1340
• Main Authors: MUELLER, Steffen, ROSENQUIST, Thomas A, TAKAI, Yoshimi, BRONSON, Richard A, WIMMER, Eckard
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Cell Adhesion Molecules - genetics; Cell Adhesion Molecules - metabolism; Epididymis - metabolism; Female; Fundamental and applied biological sciences. Psychology; Genetic Engineering - methods; Infertility, Male - genetics; Infertility, Male - pathology; Intercellular Junctions - physiology; Male; Mammalian male genital system; Mice; Mice, Inbred C57BL; Mice, Knockout; Microfilament Proteins - metabolism; Morphology. Physiology; Nectins; Oocytes - metabolism; Sertoli Cells - cytology; Sertoli Cells - metabolism; Sperm Motility - genetics; Sperm-Ovum Interactions - physiology; Spermatids - cytology; Spermatozoa - metabolism; Spermatozoa - pathology; Vertebrates: reproduction; Zona Pellucida - metabolism
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod.102.014670

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-2 LacZ/LacZ ) and analyze the resulting male-specific infertility phenotype. Although nectin-2 LacZ/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-2 LacZ/LacZ spermatozoa to the oviducts, in vitro binding to zona-intact mouse oocytes was reduced 6-fold. On the other hand, nectin-2 LacZ/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-2 LacZ/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-2 LacZ/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.