title: Annexin A2 is critical for blood-testis barrier integrity and spermatid disengagement in the mammalian testis.
abstract: Throughout spermatogenesis, two important processes occur at late stage VIII of the seminiferous epithelial cycle in the rat testis: preleptotene spermatocytes commence entry into the adluminal compartment and step 19 spermatids release from the seminiferous epithelium. Presently, it is not clear how these processes, which involve extensive restructuring of unique Sertoli-Sertoli and Sertoli-germ cell junctions, are mediated. We aimed to determine whether annexin A2 (ANXA2), a Ca2+-dependent and phospholipid-binding protein, participates in cell junction dynamics. To address this, in vitro and in vivo RNA interference studies were performed on prepubertal Sertoli cells and adult rat testes. The endpoints of Anxa2 knockdown were determined by immunoblotting, morphological analyses, fluorescent immunostaining, and barrier integrity assays. In the testis, ANXA2 localized to the Sertoli cell stalk, with specific staining at the blood-testis barrier and the concave (ventral) surface of elongated spermatids. ANXA2 also bound actin when testis lysates were used for immunoprecipitation. Anxa2 knockdown was found to disrupt the Sertoli cell/blood-testis barrier in vitro and in vivo. The disruption in barrier function was substantiated by changes in the localization of claudin-11, zona occludens-1, N-cadherin, and β-catenin. Furthermore, Anxa2 knockdown resulted in spermiation defects caused by a dysfunction of tubulobulbar complexes, testis-specific actin-rich ultrastructures that internalize remnant cell junction components prior to spermiation. Additionally, there were changes in the localization of several tubulobulbar complex component proteins, including actin-related protein 3, cortactin, and dynamin I/II. Our results indicate that ANXA2 is critical for the integrity of the blood-testis barrier and the timely release of spermatids.
authors.affiliation: Center for Biomedical Research, Population Council, 1230 York Avenue, New York, NY, USA.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Chojnacka
authors.affiliation: Department of Endocrinology, Institute of Zoology, Jagiellonian University, Gronostajowa 9, 30-387 Krakow, Poland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Bilinska
authors.affiliation: Center for Biomedical Research, Population Council, 1230 York Avenue, New York, NY, USA. Electronic address: mruk@popcbr.rockefeller.edu.
authors.forename: Dolores D
authors.initials: DD
authors.lastname: Mruk
mesh_terms: D051378:Actin-Related Protein 3 / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017306:Annexin A2 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D001814:Blood-Testis Barrier / Q000254:growth & development / Q000378:metabolism*; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D057167:Claudins / Q000235:genetics / Q000378:metabolism; D051356:Cortactin / Q000235:genetics / Q000378:metabolism; D034284:Dynamin I / Q000235:genetics / Q000378:metabolism; D034285:Dynamin II / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D007365:Intercellular Junctions / Q000235:genetics; D008297:Male; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012670:Seminiferous Epithelium / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D012708:Sertoli Cells / Q000166:cytology / Q000378:metabolism*; D015398:Signal Transduction; D013087:Spermatids / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D013090:Spermatocytes / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure; D013091:Spermatogenesis / Q000235:genetics*; D062826:Zonula Occludens-1 Protein / Q000235:genetics / Q000378:metabolism; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
chemical_list: D051378:Actin-Related Protein 3; D017306:Annexin A2; D015820:Cadherins; D057167:Claudins; C492353:Cldn11 protein, rat; D051356:Cortactin; C495268:Ctnnb1 protein, rat; C495870:Cttn protein, rat; C570099:N-cadherin, rat; D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; C569044:Tjp1 protein, rat; D062826:Zonula Occludens-1 Protein; D051176:beta Catenin; D034284:Dynamin I; D034285:Dynamin II
keywords: Cell junction; Germ cell; Sertoli cell; Spermatogenesis; Testis