Presence and localization of oscillin in human spermatozoa in relation to the integrity of the sperm membrane

Globozoospermia syndrome: An update

Among the factors involved in male infertility, there is a rare morphology disorder called "globozoospermia" that is classified into total globozoospermia and partial globozoospermia (type I and type II, respectively). This syndrome is primarily characterised by the presence of round-headed spermatozoa with cytoskeleton defects around the nucleus and no acrosome. Current data support the negative correlation between globozoospermia and conventional intracytoplasmic sperm injection (ICSI) outcomes, revealing the need for the management of patients undergoing assisted reproduction technology (ART) through more effective treatment techniques. This review highlights the most important characteristics of globozoospermia such as sperm parameters, DNA/chromatin integrity and sperm DNA fragmentation (SDF), as well as genetic features based on the latest knowledge. Additionally, we looked into current progress on fertilisation potential and possible treatment strategies for patients presenting with globozoospermia.

Estrogen receptors alpha and beta (ERalpha and ERbeta) and androgen receptor (AR) in human sperm: localization of ERbeta and AR in mitochondria of the midpiece

BACKGROUND

The central role of estrogens and androgens in the male reproductive system has focused attention on the presence and distribution of their cognate receptors [estrogen receptor (ER) alpha, ERbeta and androgen receptor (AR)] in male reproductive tissues and cells. Since the presence of steroid hormone receptors in mitochondria of mammalian cells has been well documented, we investigated the possibility of mitochondrial localization of sex steroid hormone receptors in sperm.

METHODS AND RESULTS

Applying immunofluorescence labelling and confocal laser scanning microscopy we show that the estrogen receptor beta and the AR of human sperm are specifically enriched in the midpiece, at the site of the mitochondria, which were visualized by labelling with the vital dye CMX. Nuclear and mitochondrial localization of AR was also detected in LnCap human prostate cancer cells. Differentially, most of the ERalpha immunostaining is in the form of a compact zone at a region corresponding to the equatorial segment of the upper post-acrosomal region of the sperm head. Immunoblotting experiments using sperm extracts revealed the presence of a 66 and a 45 kDa protein reacting with the ERalpha antibody, one 64 kDa protein reacting with the ERbeta antibody and a 110 and a 90 kDa protein reacting with the antibody against AR.

CONCLUSIONS

Our findings suggest that the differential localization of AR and ER isoforms in human sperm reveals distinct roles of these receptors in the physiology of sperm cells and, perhaps, also in the process of fertilization.

Immune response of the tammar wallaby (Macropus eugenii) to sperm antigens

In the present study, male and female tammar wallabies were immunised with whole tammar wallaby sperm in adjuvant. An assay for sperm antibodies using a live sperm ELISA has been developed to detect sperm surface antigens and used to validate an assay using a 3-[(3-cholamidopropyl) dimethylammonio]-1 propanesulfonate (CHAPS) membrane extract of whole tammar wallaby sperm. The tests were used to monitor the immune response to whole sperm in both male and female tammar wallabies. Antisera with a limited array of specificities were generated, with those locating to the midpiece region of the sperm appearing the most likely candidates for targets for fertility perturbation based on immunofluorescence of fixed and non-fixed sperm. These systemically generated antibodies were demonstrated to have access to both the female and male tammar reproductive tracts and were found on ejaculated sperm and antibodies from female sera and follicular fluid-labelled fresh ejaculated sperm from non-immunised males. Preliminary sequencing of these proteins has identified some possibilities for further investigation.

Egg activation at fertilization: where it all begins

A centrally important factor in initiating egg activation at fertilization is a rise in free Ca(2+) in the egg cytosol. In echinoderm, ascidian, and vertebrate eggs, the Ca(2+) rise occurs as a result of inositol trisphosphate-mediated release of Ca(2+) from the endoplasmic reticulum. The release of Ca(2+) at fertilization in echinoderm and ascidian eggs requires SH2 domain-mediated activation of a Src family kinase (SFK) and phospholipase C (PLC)gamma. Though some evidence indicates that a SFK and PLC may also function at fertilization in vertebrate eggs, SH2 domain-mediated activation of PLC gamma appears not to be required. Much work has focused on identifying factors from sperm that initiate egg activation at fertilization, either as a result of sperm-egg contact or sperm-egg fusion. Current evidence from studies of ascidian and mammalian fertilization favors a fusion-mediated mechanism; this is supported by experiments indicating that injection of sperm extracts into eggs causes Ca(2+) release by the same pathway as fertilization.

Exposure of sperm head equatorin after acrosome reaction and its fate after fertilization in mice

Equatorin is a sperm head equatorial protein, possibly involved in sperm-oocyte fusion (Toshimori et al., Biol Reprod 1998; 59:22-29). In the present work, we have shown that equatorin contained in the posterior acrosome is detectable only after spontaneous or induced acrosome reactions following fixation and permeabilization, but not in intact spermatozoa. The presence of protease inhibitors during sonication or ionophore treatments does not inhibit the exposure of the antigenic epitope. The zona-penetrated spermatozoa lying in the perivitelline space display equatorin, similar to those of the acrosome-reacted ones. After sperm-egg fusion during in vitro fertilization (IVF), the equatorin dissociates from the sperm head equatorial region and remains at the vicinity of the decondensing male pronuclei. During pronuclear apposition stage, it is pushed away from the pronuclei, possibly by the perinuclear microtubules. After first cleavage, equatorin is inherited by one of the proembryonic cells. The residual equatorin disappears after the second cleavage. Microinjected whole spermatozoa or sperm heads into the MII stage oocytes display equatorin similar to those of the perivitelline sperm. After activation, it dissociates from the sperm nuclei in a similar manner as during IVF. The mode of equatorin degeneration during fertilization is similar to those of the sperm tail components or mitochondria, but different from those of the membrane associated proteins.

Cytoplasmic inheritance and its implications for animal biotechnology

At fertilization, the mammalian sperm transmits the haploid paternal genome. However, it also carries a variety of other factors into the oocyte that have the potential to affect embryo development. These include mRNAs left over from spermatogenesis, mitochondria with their own DNA, cytoskeletal and contractile elements, remnants of the sperm plasma membrane and, in many species, the sperm centriole. While most of these elements are eliminated, some play essential roles in early embryogenesis. In this review, I summarize the latest information on these phenomena and indicate some of the implications for animal biotechnology and, in particular, cloning.

Activation of mouse oocytes requires multiple sperm factors but not sperm PLCgamma1

A sperm cytosolic factor is responsible for oocyte activation at fertilization in mammals. The molecular identity of this factor is not yet known, although a sperm phospholipase Cgamma (PLCgamma) is a potential candidate. In this study, cation-exchange chromatography with a Heparin column was used for the fractionation of porcine sperm cytosolic extracts. Oocyte activation potential of the resulting fractions was tested and active fractions were subjected to Western blot analysis using antibodies specific to PLCgamma1. PLCgamma1 was detected in fractions other than those supporting oocyte activation (Ca(2+)-release and pronuclear formation). The active Heparin fraction was then purified on a Mono Q anion-exchange column. One of the resulting fractions still contained Ca(2+)-releasing activity, but pronuclear formation did not occur. We conclude that sperm PLCgamma1 is not involved in oocyte activation and that Ca(2+)-release and pronuclear formation requires multiple factors from sperm cytosol.

Characterization of testicular mouse glucosamine 6-phosphate deaminase (GNPDA)

Mammalian glucosamine 6-phosphate deaminase (GNPDA) was first detected in hamster spermatozoa. To further elucidate its role, we have cloned mouse GNPDA and produced a polyclonal rabbit anti-GNPDA antibody. This antibody recognized a 33 kDa protein in soluble extracts from mouse brain, liver, kidney, muscle, ovary, testis and sperm. Immunofluorescent analysis of the localization of GNPDA in male reproductive tissue revealed its presence in spermatids and in spermatozoa. In spermatids, GNPDA localized close to the developing acrosome vesicle and in spermatozoa close to the acrosomal region. Following the induction of the acrosome reaction, GNPDA fluorescence in spermatozoa was either reduced or GNPDA was absent. These data suggest that GNPDA might play a role in the acrosome reaction.

Laser-assisted cryopreservation of single human spermatozoa in cell-free zona pellucida

Improved procedure for efficient cryopreservation of single human spermatozoa in cell-free human zona pellucida is reported. We used a diode laser system for efficient and precise creation of a single hole into the zona pellucida of a degenerated or immature human oocyte. This allowed the extraction of the cytoplasm using a micropipette with a diameter of 10-15 microns. Through the same opening, human spermatozoa were inserted into the empty zona. We used motile and laser immobilized spermatozoa. Immobilized sperm were obtained by a single laser irradiation delivered in the vicinity of the sperm tail prior to insertion. This new immobilization procedure was shown to have no deleterious effect on membrane integrity and sperm viability. Following sperm transfer into the zona, the laser-drilled hole was closed with an oil droplet which was expelled from the micropipette during withdrawal to avoid loss of spermatozoa. This facilitated detection of the otherwise translucent zona during the cryopreservation procedure. After thawing, all cryopreserved zonae (20/20) could be successfully retrieved. Spermatozoa were recovered from the zona pellucida through the hole used for insertion. The rate of sperm recovery for initially motile spermatozoa was 80% vs. 92% for laser immobilized spermatozoa. Sperm viability was 81% and 84%, respectively, detected by a Hoechst stain. This technique makes cryopreservation of single human spermatozoa easy and feasible and appears beneficial for couples with severe male infertility and for those facing repeated surgical sperm extraction.