title: Formin 1 Regulates Ectoplasmic Specialization in the Rat Testis Through Its Actin Nucleation and Bundling Activity.
abstract: During spermatogenesis, developing spermatids and preleptotene spermatocytes are transported across the adluminal compartment and the blood-testis barrier (BTB), respectively, so that spermatids line up near the luminal edge to prepare for spermiation, whereas preleptotene spermatocytes enter the adluminal compartment to differentiate into late spermatocytes to prepare for meiosis I/II. These cellular events involve actin microfilament reorganization at the testis-specific, actin-rich Sertoli-spermatid and Sertoli-Sertoli cell junction called apical and basal ectoplasmic specialization (ES). Formin 1, an actin nucleation protein known to promote actin microfilament elongation and bundling, was expressed at the apical ES but limited to stage VII of the epithelial cycle, whereas its expression at the basal ES/BTB stretched from stage III to stage VI, diminished in stage VII, and was undetectable in stage VIII tubules. Using an in vitro model of studying Sertoli cell BTB function by RNA interference and biochemical assays to monitor actin bundling and polymerization activity, a knockdown of formin 1 in Sertoli cells by approximately 70% impeded the tight junction-permeability function. This disruptive effect on the tight junction barrier was mediated by a loss of actin microfilament bundling and actin polymerization capability mediated by changes in the localization of branched actin-inducing protein Arp3 (actin-related protein 3), and actin bundling proteins Eps8 (epidermal growth factor receptor pathway substrate 8) and palladin, thereby disrupting cell adhesion. Formin 1 knockdown in vivo was found to impede spermatid adhesion, transport, and polarity, causing defects in spermiation in which elongated spermatids remained embedded into the epithelium in stage IX tubules, mediated by changes in the spatiotemporal expression of Arp3, Eps8, and palladin. In summary, formin 1 is a regulator of ES dynamics.
authors.affiliation: Center for Biomedical Research (N.L., D.D.M., C.Y.C.), Population Council, New York, New York 10065; Department of Biology (C.K.C.W.), Hong Kong Baptist University, Hong Kong, China; Department of Cell Biology (D.H.), Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100005, China; and School of Biological Sciences (W.M.L.), University of Hong Kong, Hong Kong, China.
authors.forename: Nan
authors.initials: N
authors.lastname: Li
authors.affiliation: Center for Biomedical Research (N.L., D.D.M., C.Y.C.), Population Council, New York, New York 10065; Department of Biology (C.K.C.W.), Hong Kong Baptist University, Hong Kong, China; Department of Cell Biology (D.H.), Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100005, China; and School of Biological Sciences (W.M.L.), University of Hong Kong, Hong Kong, China.
authors.forename: Dolores D
authors.initials: DD
authors.lastname: Mruk
authors.affiliation: Center for Biomedical Research (N.L., D.D.M., C.Y.C.), Population Council, New York, New York 10065; Department of Biology (C.K.C.W.), Hong Kong Baptist University, Hong Kong, China; Department of Cell Biology (D.H.), Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100005, China; and School of Biological Sciences (W.M.L.), University of Hong Kong, Hong Kong, China.
authors.forename: Chris K C
authors.initials: CK
authors.lastname: Wong
authors.affiliation: Center for Biomedical Research (N.L., D.D.M., C.Y.C.), Population Council, New York, New York 10065; Department of Biology (C.K.C.W.), Hong Kong Baptist University, Hong Kong, China; Department of Cell Biology (D.H.), Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100005, China; and School of Biological Sciences (W.M.L.), University of Hong Kong, Hong Kong, China.
authors.forename: Daishu
authors.initials: D
authors.lastname: Han
authors.affiliation: Center for Biomedical Research (N.L., D.D.M., C.Y.C.), Population Council, New York, New York 10065; Department of Biology (C.K.C.W.), Hong Kong Baptist University, Hong Kong, China; Department of Cell Biology (D.H.), Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100005, China; and School of Biological Sciences (W.M.L.), University of Hong Kong, Hong Kong, China.
authors.forename: Will M
authors.initials: WM
authors.lastname: Lee
authors.affiliation: Center for Biomedical Research (N.L., D.D.M., C.Y.C.), Population Council, New York, New York 10065; Department of Biology (C.K.C.W.), Hong Kong Baptist University, Hong Kong, China; Department of Cell Biology (D.H.), Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100005, China; and School of Biological Sciences (W.M.L.), University of Hong Kong, Hong Kong, China.
authors.forename: C Yan
authors.initials: CY
authors.lastname: Cheng
mesh_terms: D008841:Actin Cytoskeleton / Q000235:genetics / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D001814:Blood-Testis Barrier / Q000378:metabolism; D002450:Cell Communication / Q000235:genetics; D002478:Cells, Cultured; D005109:Extracellular Matrix / Q000235:genetics*; D005326:Fetal Proteins / Q000502:physiology*; D000080865:Formins; D008297:Male; D008840:Microfilament Proteins / Q000502:physiology*; D009687:Nuclear Proteins / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D055647:Rats, Transgenic; D012670:Seminiferous Epithelium / Q000378:metabolism; D013091:Spermatogenesis / Q000502:physiology; D013737:Testis / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D019108:Tight Junctions / Q000235:genetics*
chemical_list: D000199:Actins; D005326:Fetal Proteins; D000080865:Formins; D008840:Microfilament Proteins; D009687:Nuclear Proteins