AJ-p90: a novel protein of the perinuclear theca in human sperm subacrosome

Ultrastructural Dynamics of Human Reproduction, from Ovulation to Fertilization and Early Embryo Development1

This study describes the updated, fine structure of human gametes, the human fertilization process, and human embryos, mainly derived from assisted reproductive technology (ART). As clearly shown, the ultrastructure of human reproduction is a peculiar multistep process, which differs in part from that of other mammalian models, having some unique features. Particular attention has been devoted to the (1) sperm ultrastructure, likely "Tygerberg (Kruger) strict morphology criteria"; (2) mature oocyte, in which the MII spindle is barrel shaped, anastral, and lacking centrioles; (3) three-dimensional microarchitecture of the zona pellucida with its unique supramolecular filamentous organization; (4) sperm-egg interactions with the peculiarity of the sperm centrosome that activates the egg and organizes the sperm aster and mitotic spindles of the embryo; and (5) presence of viable cumulus cells whose metabolic activity is closely related to egg and embryo behavior in in vitro as well as in vivo conditions, in a sort of extraovarian "microfollicular unit." Even if the ultrastructural morphodynamic features of human fertilization are well understood, our knowledge about in vivo fertilization is still very limited and the complex sequence of in vivo biological steps involved in human reproduction is only partially reproduced in current ART procedures.

Characterization of boar sperm cytoskeletal cylicin II as an actin-binding protein

The presence of actin-binding proteins in the perinuclear theca of boar spermatozoa has been investigated, using stepwise extractions of proteins from sperm heads. Proteins extracted with the alkaline buffer 1M Na(2)CO(3), pH 11, were found to contain a 66kDa protein that binds F-actin in actin pelleting assays. Sequence studies and immunological characterization with antibodies specific for human cylicin II identified the 66kDa protein as the homologue of bovine and human cylicin II. Immunocytochemical studies showed the presence of porcine cylicin II in the acrosomal region of round spermatids and in the postacrosomal region of late spermatids and spermatozoa, in agreement with the previously described localization of cylicins. Taken together, the results suggest that cylicin II, a protein of the sperm perinuclear cytoskeleton, is a novel actin-binding protein, which probably plays a role in the actin-related events that occur during spermiogenesis and the early events of fertilization.

Actin-binding properties and colocalization with actin during spermiogenesis of mammalian sperm calicin

The nucleus of mammalian spermatozoa is surrounded by a rigid layer, the perinuclear theca, which is divided into a subacrosomal layer and a postacrosomal calyx. Among the proteins characterized in the perinuclear theca, calicin is one of the main components of the calyx. Its sequence contains three kelch repeats and a BTB/POZ domain. We have studied the association of boar calicin with F-actin and the distribution of boar and human calicin during spermiogenesis compared with the distribution of actin. Calicin was purified from boar sperm heads under nondenaturating conditions. The molecule bound actin with high affinity (K(d) = approximately 5 nM), and a stoichiometry of approximately one calicin per 12 actin monomers was observed. Gel filtration studies showed that calicin forms homomultimers (tetramers and higher polymers). According to immunocytochemical results, calicin is present (together with actin) in the acrosomal region of round spermatids and is mainly localized in the postacrosomal region of late spermatids and spermatozoa. Taken together, the results suggest that the affinity of calicin to F-actin allows targeting of calicin at the subacrosomal space of round spermatids, and that its ability to form homomultimers contributes to the formation of a rigid calyx.

Heterogeneity in the presence of CD4-like molecules on human spermatozoa

The object of the present study was to study if there are differences in the presence of CD4-like molecules on human ejaculated spermatozoa in fertile donors and infertile patients (with globozoospermia). Indirect and absorption enzyme-linked immunosorbent assay and indirect immunofluorescence were applied. The enzyme-linked immunosorbent assay data showed that monoclonal anti-human CD4-antibody recognizes an epitope common to the human spermatozoa with normal morphology and round-headed spermatozoa. Localization of the antigenic determinants, identified by anti-human CD4-monoclonal antibody, in the acrosomal region, including equatorial segment, postnuclear cap and tail was determined in normozoospermic samples. A positive reaction was found on the sperm head both in the acrosomal and postacrosomal region of some round-headed spermatozoa in the samples with globozoospermia. The tails of the normozoospermic spermatozoa and of some round-headed spermatozoa were weakly immunopositive. The results of the experiments carried out are evidence of heterogeneity in the presence of CD4-like antigen determinants on human spermatozoa. These data increased the information about the CD4-antigen characteristic of the spermatozoa from fertile donors and infertile patients.

The monoclonal antibody GZS-1 detects a maturation-associated antigen of human spermatozoa that is also present on the surface of human mononuclear blood cells

A monoclonal antibody (GZS-1) has been generated by fusion of mouse myeloma cells with spleen cells from BALB/c mice immunised with human sperm cells. The antibody was determined to be an IgG1. The corresponding antigen is present on the whole surface of ejaculated human spermatozoa. It is not detectable on spermatozoa of other mammalian species (rabbit, cat, dog, sheep, boar, bull, horse). In human male genital organs, immunostaining with GZS-1 is observed on sperm cells in the epididymis and the ductus deferens together with the lining epithelium of those organs. No reactivity of sperm cells or germ cell precursors in the testis has been detected. Functional tests using the antibody show a strong inhibitory effect of human sperm in the hamster egg penetration assay. Furthermore, the GZS-1 antigen is detectable on the surface of human lymphocytes and monocytes by immunogold electron microscopy and FACS analysis. By Western blotting of human sperm and seminal plasma performed under reducing conditions immunostaining was detected at 21-25, 31, 51-54, and 62 kDa. The reaction with human lymphocytes shows one major band at 62 kDa and additional bands at 31 and 54 kDa. The results suggest that the monoclonal antibody GZS-1 may recognise an antigen which is secreted from the epithelial cells of the epididymis and binds to ejaculated spermatozoa as a sperm coating antigen. This component may be involved in the capacitation of the sperm and the acrosome reaction. Molecules that are expressed both on sperm and on immunocompetent cells may be relevant for the regulation of immunological processes or for the development of the related immunological tolerance of sperm in the female reproductive tract.