title: Appearance of an oocyte activation-related substance during spermatogenesis in mice and humans.
abstract: BACKGROUND
  Recently we reported that an oocyte activation ability in human and mouse sperm is associated with head flatness or the presence of perinuclear theca (PT) substance, MN13, which is an oocyte activation-related protein localized on the post-acrosomal sheath (PAS). As such, we hypothesize that the appearance of oocyte activation ability is stage-specifically regulated and depends on the formation of the acrosome or PAS/PT in spermatids.
  
  
  METHODS
  We monitored the appearance and movement of MN13 as a PT-specific molecule during spermatogenesis and analysed how the MN13 localization is affected in mouse and human globozoospermic acrosomeless sperm.
  
  
  RESULTS
  MN13 was first detected on the surface of acrosomic vesicles, i.e. on the nascent outer acrosomal membrane of step 5-6 round spermatids (Sb1 spermatids in human), and it was then translocated via the outer acrosomal membrane surface to the most distal region of the acrosome in step 7 round spermatids (Sb2 spermatids). As spermatids elongated, MN13 was translocated via the cytoplasmic space between the nuclear envelope and the overlying plasma membrane towards the post-acrosomal region, and it was organized on the top of the nascent PAS that was typically found in step 14 elongated spermatids (Sd1 spermatids). In contrast, MN13 was not found in any GOPC-deficient spermatids, which completely lack the acrosome but have manchettes (microtubule bundles), nor in mouse and human acrosomeless sperm.
  
  
  CONCLUSIONS
  The MN13 appearance or the MN13-related PAS/PT formation is highly dependant on acrosome formation; the MN13-related oocyte activation factor/ability is stage-specifically acquired in elongating/elongated spermatids.
authors.affiliation: Department of Anatomy and Developmental Biology, Graduate School of Medicine, Chiba University, Chuo-ku, Chiba, Japan.
authors.forename: Chizuru
authors.initials: C
authors.lastname: Ito
authors.forename: Kenji
authors.initials: K
authors.lastname: Yamatoya
authors.forename: Keiichi
authors.initials: K
authors.lastname: Yoshida
authors.forename: Koichi
authors.initials: K
authors.lastname: Kyono
authors.forename: Ryoji
authors.initials: R
authors.lastname: Yao
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Noda
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Toshimori
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D008870:Microtubules / Q000378:metabolism; D008875:Middle Aged; D009865:Oocytes / Q000502:physiology*; D013087:Spermatids / Q000378:metabolism; D013091:Spermatogenesis / Q000276:immunology*; D013094:Spermatozoa / Q000002:abnormalities; D013737:Testis / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal