A model of the acrosome reaction progression via the acrosomal membrane-anchored protein equatorin.
It is important to establish a reliable and progressive model of the acrosome reaction. Here, we present a progression model of the acrosome reaction centering around the acrosomal membrane-anchored protein equatorin (MN9), comparing the staining pattern traced by MN9 antibody immunofluorescence with that traced by Arachis hypogaea agglutinin (PNA)-FITC. Prior to the acrosome reaction, equatorin was present in both the anterior acrosome and the equatorial segment. Since sperm on zona pellucida showed various staining patterns, MN9-immunostaining patterns were classified into four stages: initial, early, advanced, and final. As the acrosome reaction progressed from the initial to the early stage, equatorin spread from the peripheral region of the anterior acrosome toward the center of the equatorial segment, gradually over the entire region of the equatorial segment during the advanced stage, and finally uniformly at the equatorial segment at the final stage. In contrast, the PNA-FITC signals spread more quickly from the peripheral region of the acrosome toward the entire equatorial segment, while decreasing in staining intensity, and finally became weak at the final stage. MN9-immunogold electron microscopy showed equatorin on the hybrid vesicles surrounded by amorphous substances at advanced stage of acrosome reaction. Equatorin decreased in molecular mass from 40-60 to 35 kDa, and the signal intensity of 35 kDa equatorin increased as the acrosome reaction progressed. Thus, the established equatorin-based progression model will be useful for analyzing not only the behavior of equatorin but also of other molecules of interest involved in the acrosome reaction.
Yoshida
Keiichi
K
Department of Anatomy and Developmental Biology, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan.
Ito
Chizuru
C
Yamatoya
Kenji
K
Maekawa
Mamiko
M
Toyama
Yoshiro
Y
Suzuki-Toyota
Fumie
F
Toshimori
Kiyotaka
K
D000177:Acrosome / Q000187:drug effects / Q000378:metabolism; D020101:Acrosome Reaction / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D005260:Female; D008297:Male; D008565:Membrane Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D051379:Mice; D008813:Mice, Inbred ICR; D008954:Models, Biological; D008970:Molecular Weight; D011247:Pregnancy; D013329:Structure-Activity Relationship; D013997:Time Factors
D000911:Antibodies, Monoclonal; C512717:Eqtn protein, mouse; D008565:Membrane Proteins