A role for the disintegrin domain of cyritestin, a sperm surface protein belonging to the ADAM family, in mouse sperm-egg plasma membrane adhesion and fusion

Ovine fertility by artificial insemination in the breeding season could be affected by intraseasonal variations in ram sperm proteomic profile

It is important to note that seasonality could affect ram reproductive parameters, and therefore, fertility results after artificial insemination. In this work, 1) we assessed fertility rates after cervical artificial insemination of 11,805 ewes at the beginning (June 21st to July 20th) and at the end (November 20th to December 21st) of the reproductive season in the Assaf breed for the last four years, and 2) we aimed to identify male factors influencing the different reproductive success obtained depending on the time at the mating season in which ovine artificial insemination was performed. For this purpose, we evaluated certain ram reproductive and ultrasonographical parameters as well as we performed a multiparametric and proteomic sperm analysis of 6-19 rams at two very distant points in the mating season (July as Early Breeding Season -EBS- and November as Late Breeding Season -LBS-). Rutinary assessments carried out in the ovine reproduction centers (testicular volume, libido, sperm production and mass motility) showed non-significant differences (P ≥ 0.05) between both studied times, as well as the ram ultrasonographic evaluation (Resistive and Pulsatility Index as Doppler parameters; and pixels mean gray level, and hypoechoic areas percentage and density as echotexture parameters). However, at level of sperm functionality, although sperm quality appeared non-significantly lower (P ≥ 0.05) in the EBS, we identified a significantly different (P < 0.05) sperm proteomic profile between the seasonality points. The following proteins were identified with the lowest abundance in the EBS with a fold change > 4, a P = 2.40e-07, and a q = 2.23e-06: Fibrous Sheath-Interacting Protein 2, Disintegrin and Metalloproteinase Domain-Containing Protein 20-like, Phosphoinositide-Specific Phospholipase C, Tektin 5, Armadillo Repeat-Containing Protein 12 Isoform X3, Solute Carrier Family 9B1, Radial Spoke Head Protein 3 Homolog, Pro-Interleukin-16, NADH Dehydrogenase [Ubiquinone] 1 Alpha Subcomplex Subunit 8, Testis, Prostate and Placenta-Expressed Protein, and Acyl Carrier Protein Mitochondrial. In conclusion, while our basic analyses on male and sperm quality showed similar results between the beginning and the end of the breeding season, on a proteomic level we detected a lower expression of sperm proteins linked to the energy metabolism, sperm-oocyte interactions, and flagellum structure in the EBS. Probably, this different protein expression could be related to the lower fertility rate of Assaf ewes after cervical artificial insemination at this time. More importantly, sperm proteins can be used as highly effective molecular markers in predicting sperm fertilization ability related to intraseasonal variations.

The EGF-motif-containing protein SPE-36 is a secreted sperm protein required for fertilization in C. elegans

Identified through forward genetics, spe-9 was the first gene to be identified in C. elegans as necessary for fertilization.1 Since then, genetic screens in C. elegans have led to the identification of nine additional sperm genes necessary for fertilization (including spe-51 reported by Mei et al.2 and the spe-36 gene reported here).3,4,5,6,7,8,9 This includes spe-45, which encodes an immunoglobulin-containing protein similar to the mammalian protein IZUMO1, and spe-42 and spe-49, which are homologous to vertebrate DCST2 and DCST1, respectively.4,7,8,10,11,12,13 Mutations in any one of these genes result in healthy adult animals that are sterile. Sperm from these mutants have normal morphology, migrate to and maintain their position at the site of fertilization in the reproductive tract, and make contact with eggs but fail to fertilize the eggs. This same phenotype is observed in mammals lacking Izumo1, Spaca6, Tmem95, Sof1, FIMP, or Dcst1 and Dcst2.10,14,15,16,17,18,19 Here we report the discovery of SPE-36 as a sperm-derived secreted protein that is necessary for fertilization. Mutations in the Caenorhabditis elegans spe-36 gene result in a sperm-specific fertilization defect. Sperm from spe-36 mutants look phenotypically normal, are motile, and can migrate to the site of fertilization. However, sperm that do not produce SPE-36 protein cannot fertilize. Surprisingly, spe-36 encodes a secreted EGF-motif-containing protein that functions cell autonomously. The genetic requirement for secreted sperm-derived proteins for fertilization sheds new light on the complex nature of fertilization and represents a paradigm-shifting discovery in the molecular understanding of fertilization.

The metalloprotease ADM-4/ADAM17 promotes axonal repair

Axonal fusion is an efficient means of repair following axonal transection, whereby the regenerating axon fuses with its own separated axonal fragment to restore neuronal function. Despite being described over 50 years ago, its molecular mechanisms remain poorly understood. Here, we demonstrate that the Caenorhabditis elegans metalloprotease ADM-4, an ortholog of human ADAM17, is essential for axonal fusion. We reveal that animals lacking ADM-4 cannot repair their axons by fusion, and that ADM-4 has a cell-autonomous function within injured neurons, localizing at the tip of regrowing axon and fusion sites. We demonstrate that ADM-4 overexpression enhances fusion to levels higher than wild type, and that the metalloprotease and phosphatidylserine-binding domains are essential for its function. Last, we show that ADM-4 interacts with and stabilizes the fusogen EFF-1 to allow membranes to merge. Our results uncover a key role for ADM-4 in axonal fusion, exposing a molecular target for axonal repair.

Evolution of Fertilization-Related Genes Provides Insights Into Reproductive Health in Natural Ascrotal Mammals

Cryptorchidism is the failure of one or both testes to descend into the bottom of the scrotum. This common congenital malformation in humans and domestic animals is the best characterized risk factor for abnormal sperm functions and infertility. However, current treatment approaches for cryptorchidism do not ensure paternity in all cases. Some lineages of mammals (such as elephants and cetaceans) have natural ascrotal testes (i.e., undescended or incompletely descended testes) and normal sperm motility and fertility, providing an opportunity to understand the genetic basis of cryptorchidism. In this study, we showed that genes associated with sperm motility and competition/fertility in ascrotal mammals experienced frequent, strong selective pressure. The fixation of specific amino acids and positive selection in ascrotal mammals could affect the physicochemical properties and functions of fertilization-related proteins. In a comparison between mammals with undescended testes and incompletely descended testes, discrepancies in genes showing evidence for adaptive evolution and in functional enrichment suggested that multiple molecular mechanisms contribute to the maintenance of fertility in the challenging testicular environment. Our findings revealed substantial heterogeneity in the divergence of fertilization-related genes between natural scrotal and ascrotal mammals and provide insight into molecular mechanisms underlying normal sperm motility and competition in natural ascrotal mammals. We provide a detailed theoretical basis for understanding the pathology of cryptorchidism from a molecular evolutionary perspective. This study may contribute to the establishment of diagnostic and therapeutic targets for sperm motility and fertility disorders due to congenital cryptorchidism in humans and domestic animals.

Cyclic fertilin-derived peptide stimulates in vitro human embryo development

OBJECTIVE

To study the cyclic fertilin peptide effects on preimplantation human embryogenesis. Cyclic fertilin peptide reproduces the structure of the binding site of the sperm Fertilin β (also named A Disintegrin and Metalloprotease 2: ADAM2) disintegrin domain. It binds to the oocyte membrane and increases sperm-oocyte fusion index in human and fertilization rate in mouse, providing healthy pups. It also improves human oocyte maturation and chromosome segregation in meiosis I and binds to human embryo blastomeres, suggesting that it has a membrane receptor.

DESIGN

Thawed human embryos at the 3 to 4 cells stage were randomly included in a dose-response study with cyclic fertilin peptide. Inner cell mass (ICM), trophectoderm (TE), and total cell numbers were evaluated in top- and good-quality blastocysts.

SETTING

The study was performed in an academic hospital and research laboratory.

PATIENT(S)

Human embryos donated for research. This project was approved by the French "Agence de la Biomédecine."

INTERVENTION(S)

Immunofluorescence and tissue-specific gene expression analysis, using Clariom D microarrays, were performed to study its mechanism of action.

MAIN OUTCOME MEASURE(S)

Cyclic fertilin peptide improves blastocyst formation by almost 20%, the concentration of 1 μM being the lowest most efficient concentration. It significantly increases twice the TE cell number, without modifying the ICM. It increases the in vitro hatching rate from 14% to 45%.

RESULT(S)

Cyclic fertilin peptide stimulates TE growth. In the ICM, it induces transcriptional activation of intracellular protein and vesicle-mediated transport.

CONCLUSION(S)

Cyclic fertilin peptide dramatically improves human embryo development potential. It could be used to supplement culture medium and improve the in vitro human embryo development. Starting supplementation immediately after fertilization, instead of day 2, could significantly upgrade assisted reproductive technology outcome.

A fertilin-derived peptide improves in vitro maturation and ploidy of human oocytes

OBJECTIVE

To analyze the effect of a cyclic fertilin-derived peptide (cFEE) on in vitro maturation of human oocytes.

DESIGN

Randomized study.

SETTING

Fertility center in an academic hospital.

PATIENT(S)

Not applicable.

INTERVENTION(S)

Human immature germinal vesicle-stage oocytes (n = 1,629) donated for research according to French bioethics laws were randomly allocated to groups treated with 1 or 100 μM of cFEE or to a control group. They were incubated at 37 °C in 6% CO₂ and 5% O₂, and their maturation was assessed using time-lapse microscopy over 24 hours. In vitro maturated metaphase II oocytes were analyzed for chromosomal content using microarray comparative genomic hybridization, and their transcriptomes were analyzed using Affymetrix Clariom D microarrays.

MAIN OUTCOME MEASURE(S)

The percentage of oocytes undergoing maturation in vitro was observed. Aneuploidy and euploidy were assessed for all chromosomes, and differential gene expression was analyzed in oocytes treated with cFEE compared with the control to obtain insights into its mechanism of action.

RESULT(S)

cFEE significantly increased the percentage of oocytes that matured in vitro and improved euploidy in meiosis II oocytes by the up-regulation of FMN1 and FLNA genes, both of which encode proteins involved in spindle structure.

CONCLUSION(S)

cFEE improves human oocyte maturation in vitro and reduces aneuploidy. It may prove useful for treating oocytes before fertilization in assisted reproductive technology and for in vitro maturation in fertility preservation programs to improve oocyte quality and the chances for infertile couples to conceive.

Immunolocalization of Fertilin β, IZUMO1, and P34H in Ram Spermatozoa

According to various reports, current methods of sperm freezing destroy the integrity of the sperm plasma membrane and acrosome. This study aimed to determine the changes in the existence and location of three proteins, namely fertilin β, IZUMO1, and P34H, in ram spermatozoa. By using frozen-thawed spermatozoa, ejaculated fresh spermatozoa, and testicular and epididymal spermatozoa (obtained from caput, corpus, and caudal regions), the localizations of the mentioned proteins were performed using signal labeling with indirect immunofluorescence, and the quantification of these proteins was compared using Western blot analyses. Moreover, protein localization and signal labeling in fresh and frozen-thawed spermatozoa subjected to in vitro capacitation and acrosome reaction were compared. Using chlortetracycline (CTC) staining, as expected, it was detected that after incubating for 4 hours under capacitating conditions related to the control sample (0 hour), capacitated and acrosome-reacted sperm were increased (p < 0.001). Frozen-thawed samples had a lower density and expression than the ejaculate samples. Expression was not obtained, except for IZUMO1, from samples that underwent in vitro capacitation/acrosome reactions. Expression of IZUMO1 was seen as an increasing band formation from the equatorial region through the acrosome, after in vitro capacitation. However, after the acrosome reaction, the band formation was only on the equatorial region. Region-specific differences of proteins at the kDa level were obtained using Western blot analysis and possible isoforms specific to ram spermatozoa or proteins with similar epitopes were expressed. Considering the changes in surface proteins in frozen-thawed sperm, it is suggested that fertilin β and P34H can be used as fertility or freezability markers.

Localization and expression of ADAM2 in the dromedary camel testis, epididymis and sperm during rutting season

ADAM2 (fertilin β) is a sperm surface protein reported in several mammalian species. However, the presence of ADAM2 in the male reproductive system and sperm of the camel is not well known. The present study was to clarify the localization and expression of ADAM2 in the dromedary camel testis, epididymis and spermatozoa during rutting season using immunohistochemistry (IHC) and the quantitative real-time polymerase chain reaction (qPCR). Tissue samples were obtained from the testis (proximal and distal) and epididymis (caput, corpus, and cauda) from eight mature male camels. Epididymal and ejaculated sperms were collected from four other fertile camels. IHC analysis clearly showed the localization of ADAM2 protein in the spermatocytes and the round and elongated spermatids of the testis, in the epithelial cells along the epididymis tract, on the posterior head of the sperm within the cauda epididymis, and on the acrosomal cap of both the epididymal and ejaculated sperm. The expression of camel ADAM2 mRNA was significantly higher (P < 0.05) in the testis when compared with the epididymis. These findings may suggest an important role of ADAM2 in the fertility of male dromedary camels.

The enigmatic sperm proteins in mammalian fertilization: an overview†

Mammalian fertilization involves a physical interaction between a sperm and an egg followed by molecular interactions amongst their various cell surface molecules. These interactions are initially mediated on the egg's outermost matrix, zona pellucida (ZP), and then its plasma membrane. To better understand this process, it is pertinent to find the corresponding molecules on sperm that interact with ZP or the egg's plasma membrane. Although currently, we have some knowledge about the binding partners for egg's plasma membrane on sperm, yet the ones involved in an interaction with ZP have remained remarkably elusive. This review provides comprehensive knowledge about the various sperm proteins participating in mammalian fertilization and discusses the possible reasons for not being able to identify the strong sperm surface candidate (s) for ZP adhesion. It also hypothesizes the existence of a multi-protein complex(s), members of which participate in oviduct transport, cumulus penetration, zona adhesion, and adhesion/fusion with the egg's plasma membrane; with some protein(s) having multiple roles during this process. Identification of these proteins is crucial as it improves our understanding of the process and allows us to successfully treat infertility, develop contraceptives, and improve artificial reproductive technologies.

The evolution of ADAM gene family in eukaryotes

The ADAM (A Disintegrin And Metalloprotease) gene family encodes proteins with adhesion and proteolytic functions. ADAM proteins are associated with diseases like cancers. Twenty ADAM genes have been identified in humans. However, little is known about the evolution of the family. We analyzed the repertoire of ADAM genes in a vast number of eukaryotic genomes to clarify the main gene copy number expansions. For the first time, we provide compelling evidence that early-branching green algae (Mamiellophyceae) have ADAM genes, suggesting that they originated in the last common ancestor of eukaryotes, before the split of plants, fungi and animals. The ADAM family expanded in early metazoans, with the most significative gene expansion happening during the first steps of vertebrate evolution. We concluded that most of mammal ADAM diversity can be explained by gene duplications in early bone fish. Our data suggest that ADAM genes were lost early in green plant evolution.

Adhesion molecules in gamete transport, fertilization, early embryonic development, and implantation-role in establishing a pregnancy in cattle: A review

Cell-cell adhesion molecules have critically important roles in the early events of reproduction including gamete transport, sperm-oocyte interaction, embryonic development, and implantation. Major adhesion molecules involved in reproduction include cadherins, integrins, and disintegrin and metalloprotease domain-containing (ADAM) proteins. ADAMs on the surface of sperm adhere to integrins on the oocyte in the initial stages of sperm-oocyte interaction and fusion. Cadherins act in early embryos to organize the inner cell mass and trophectoderm. The trophoblast and uterine endometrial epithelium variously express cadherins, integrins, trophinin, and selectin, which achieve apposition and attachment between the elongating conceptus and uterine epithelium before implantation. An overview of the major cell-cell adhesion molecules is presented and this is followed by examples of how adhesion molecules help shape early reproductive events. The argument is made that a deeper understanding of adhesion molecules and reproduction will inform new strategies that improve embryo survival and increase the efficiency of natural mating and assisted breeding in cattle.

Disorder-to-Order Markers of a Cyclic Hexapeptide Inspired from the Binding Site of Fertilin β Involved in Fertilization Process

Synthetic peptides mimicking the binding site of fertilin β to its receptor, integrin α6β1, were shown to inhibit sperm-egg fusion when added to in vitro media. In contrast, the synthetic cyclic hexapeptide, cyclo(Cys¹-Ser²-Phe³-Glu⁴-Glu⁵-Cys⁶), named as cFEE, proved to stimulate gamete fusion. Owing to its biological specificity, this hexapeptide could help improve the in vitro fertilization pregnancy rate in human. In an attempt to establish the structure-activity relationship of cFEE, its structural dynamics was herein analyzed by means of ultraviolet circular dichroism (UV-CD) and Raman scattering. The low concentration CD profile in water, containing mainly a deep minimum at ∼202 nm, is consistent with a rather unordered chain. However, an ordering trend of the peptide loop has been observed in a less polar solvent such as methanol, where the UV-CD signal shape is formed by a double negative marker at ∼202/215 nm, indicating the presence of a type-II' β-turn. Raman spectra recorded in aqueous samples upon a 100-fold concentration increase, still showed an important population (∼30%) of the disordered structure. The structural flexibility of the disulfide bridge was confirmed by the Raman markers arising from the Cys¹-Cys⁶ disulfide bond-stretch motions. Density functional theory calculations highlighted the formation of the type-II' β-turn on the four central residues of cFEE (i.e., -Ser²-Phe³-Glu⁴-Glu⁵-) either with a left- or with a right-handed disulfide. The structure with a left-handed S-S bond, however, appears to be more stable.

Assessing the potential of HSPA2 and ADAM2 as two biomarkers for human sperm selection

Selection of the best sperm, with the least defects, is a critical factor in the success of ART especially in male factor infertility. This study assessed the potential Heat shock protein (HSPA2) and metallopeptidase domain2 (ADAM2) biomarkers for sperm selection. Sperm were obtained from 72 asthenoteratozoospermic and 42 normospermic ejaculates. The semen characteristic, DNA fragmentation (DFI), chromatin maturation index (CMI), ADAM2 and HSPA2 levels on sperm, and their correlation with embryo quality were assessed in both groups. Results showed the significant reduction in HSPA2 and ADAM2 in asthenoteratozoospermic compared to normazoospermic ejaculates regarding the cut-off value of 14 and 13% for these two biomarkers. The specificity of HSPA2 and ADAM2 separately, and the combination of these two biomarkers, were 95.2, 90.5 and 93.5%, respectively, for sperm from normozoospermic ejaculates. However, they were 48.6, 50.0 and 54.5% for asthenoteratozoospermic ones. A significant correlation was observed with HSPA2, ADAM2 and a combination of these two biomarkers with CMI, DFI and embryo quality. Although a combination of these two biomarkers have the potential to be a good choice for selecting sperm with the lowest level of chromatin damage, it seems that selection according to HSPA2 has priority over ADAM2 or a combination of the two.

ADAM proteases involved in inflammation are differentially altered in patients with gastritis or ulcer

ADAM metallopeptidase domain (ADAM)9, 10 and 17 have α-secretase activity that regulates ectodomain shedding of factors involved in inflammation, cell proliferation, angiogenesis, and wound healing. The secretase activity of ADAM proteins is known to induce an inflammatory response. However, under certain conditions, a lack of secretase activity may induce inflammation suggesting differential roles of ADAM proteins with secretase activity. To the best of our knowledge, the present study evaluated the changes in α-secretase activity and expression of associated ADAM proteases (ADAM9, 10 and 17) in the gastric mucosa of patients with gastritis and ulcers, for the first time. Gastroduedonal mucosal samples from 42 patients were snap-frozen to determine changes in α-secretase activity. Twenty-four of these patients had gastritis, 9 patients had duedonal ulcers and 9 patients did not have any pathological changes. Paraffin-embedded gastric specimens (n=32) were used for immunohistochemical detection of ADAM9, ADAM10 and ADAM17. α-secretase activity of the gastric mucosa of healthy subjects was significantly higher compared with the uninvolved mucosa of patients with gastritis or ulcer. These results were associated with the immunohistochemical staining results, which demonstrated that ADAM10 expression markedly decreased in glandular epithelial cells and ADAM9 expression was lost in foveolar epithelial cells of gastric mucosa adjacent to ulcer. However, ADAM17 expression was increased in the normal gastric mucosa of patients with bleeding peptic ulcers and in the gastric mucosa adjacent to the ulcer suggesting a counteracting role of ADAM17. Decreased ADAM9 and 10 expression, and an associated decrease in α-secretase activity may predispose to chronic gastritis and ulcer. Further studies are required to determine the possible etiological role of increased ADAM17 expression.

Acrosome markers of human sperm

Molecular biomarkers that can assess sperm acrosome status are very useful for evaluating sperm quality in the field of assisted reproductive technology. In this review, we introduce and discuss the localization and function of acrosomal proteins that have been well studied. Journal databases were searched using keywords, including "human acrosome", "localization", "fertilization-related protein", "acrosomal membrane", "acrosomal matrix", "acrosome reaction", "knockout mouse", and "acrosome marker".

Bovine sperm plasma membrane proteomics through biotinylation and subcellular enrichment

A significant proportion of mammalian fertilization is mediated through the proteomic composition of the sperm surface. These protein constituents can present as biomarkers to control and regulate breeding of agricultural animals. Previous studies have addressed the bovine sperm cell apical plasma membrane (PM) proteome with nitrogen cavitation enrichment. Alternative workflows would enable to expand the compositional data more globally around the entire sperm's surface. We used a cell surface biotin-labeling in combination with differential centrifugation to enrich sperm surface proteins. Using nano-LC MS/MS, 338 proteins were confidently identified in the PM-enriched proteome. Functional categories of sperm-egg interaction, protein turnover, metabolism as well as molecular transport, spermatogenesis, and signal transduction were represented by proteins with high quantitative signal in our study. A highly significant degree of enrichment was found for transmembrane and PM-targeted proteins. Among them, we also report proteins previously not described on bovine sperm (CPQ, CD58, CKLF, CPVL, GLB1L3, and LPCAT2B) of which CPQ and CPVL cell surface localization was further validated. A descriptive overview of the bovine sperm PM integral and peripheral proteins is provided to complement future studies on animal reproduction and its relation to sperm cell surface. All MS data have been deposited in the ProteomeXchange with identifier PXD001096 (http://proteomecentral.proteomexchange.org/dataset/PXD001096).

Molecular and cellular mechanisms of sperm-oocyte interactions opinions relative to in vitro fertilization (IVF)

One of the biggest prerequisites for pregnancy is the fertilization step, where a human haploid spermatozoon interacts and penetrates one haploid oocyte in order to produce the diploid zygote. Although fertilization is defined by the presence of two pronuclei and the extraction of the second polar body the process itself requires preparation of both gametes for fertilization to take place at a specific time. These preparations include a number of consecutive biochemical and molecular events with the help of specific molecules and with the consequential interaction between the two gametes. These events take place at three different levels and in a precise order, where the moving spermatozoon penetrates (a) the outer vestments of the oocyte, known as the cumulus cell layer; (b) the zona pellucida (ZP); where exocytosis of the acrosome contents take place and (c) direct interaction of the spermatozoon with the plasma membrane of the oocyte, which involves a firm adhesion of the head of the spermatozoon with the oocyte plasma membrane that culminates with the fusion of both sperm and oocyte membranes (Part I). After the above interactions, a cascade of molecular signal transductions is initiated which results in oocyte activation. Soon after the entry of the first spermatozoon into the oocyte and oocyte activation, the oocyte’s coat (the ZP) and the oocyte’s plasma membrane seem to change quickly in order to initiate a fast block to a second spermatozoon (Part II). Sometimes, two spermatozoa fuse with one oocyte, an incidence of 1%–2%, resulting in polyploid fetuses that account for up to 10%–20% of spontaneously aborted human conceptuses. The present review aims to focus on the first part of the human sperm and oocyte interactions, emphasizing the latest molecular and cellular mechanisms controlling this process.

Immunocontraceptives: new approaches to fertility control

The rapidly increasing global population has bowed the attention of family planning and associated reproductive health programmes in the direction of providing a safe and reliable method which can be used to limit family size. The world population is estimated to exceed a phenomenal 10 billion by the year 2050 A.D., thus presenting a real jeopardy of overpopulation with severe implications for the future. Despite the availability of contraceptive methods, there are over one million elective abortions globally each year due to unintended pregnancies, having devastating impact on reproductive health of women worldwide. This highlights the need for the development of newer and improved contraceptive methods. A novel contraceptive approach that is gaining substantial attention is "immunocontraception" targeting gamete production, gamete outcome, or gamete function. Amongst these, use of sperm antigens (gamete function) seems to be an exciting and feasible approach. However, the variability of immune response and time lag to attain titer among vaccinated individuals after active immunization has highlighted the potential relevance of preformed antibodies in this league. This review is an attempt to analyze the current status and progress of immunocontraceptive approaches with respect to their establishment as a future fertility control agent.

SAS1B protein [ovastacin] shows temporal and spatial restriction to oocytes in several eutherian orders and initiates translation at the primary to secondary follicle transition

BACKGROUND

Sperm Acrosomal SLLP1 Binding (SAS1B) protein (ovastacin) is an oolemmal binding partner for the intra-acrosomal sperm protein SLLP1.

RESULTS

Immunohistochemical localization revealed that SAS1B translation is restricted among adult tissues to the ovary and oocytes, SAS1B appearing first in follicles at the primary-secondary transition. Quiescent oocytes within primordial follicles and primary follicles did not stain for SAS1B. Examination of neonatal rat ovaries revealed SAS1B expression first as faint signals in postnatal day 3 oocytes, with SAS1B protein staining intensifying with oocyte growth. Irrespective of animal age or estrus stage, SAS1B was seen only in oocytes of follicles that initiated a second granulosa cell layer. The precise temporal and spatial onset of SAS1B expression was conserved in adult ovaries in seven eutherian species, including nonhuman primates. Immunoelectron micrographs localized SAS1B within cortical granules in MII oocytes. A population of SAS1B localized on the oolemma predominantly in the microvillar region anti-podal to the nucleus in ovulated MII rat oocytes and on the oolemma in macaque GV oocytes.

CONCLUSIONS

The restricted expression of SAS1B protein in growing oocytes, absence in the ovarian reserve, and localization on the oolemma suggest this zinc metalloprotease deserves consideration as a candidate target for reversible female contraceptive strategies.

Critical role of exosomes in sperm-egg fusion and virus-induced cell-cell fusion

In mammals, two integral membrane proteins, sperm IZUMO1 and egg CD9, regulate sperm-egg fusion, and their roles are critical, but yet unclear. Recent studies, however, indicate interesting connections between the sperm-egg fusion and virus-induced cell-cell fusion. First, CD9-containing exosome-like vesicles, which are released from wild-type eggs, can induce the fusion between sperm and CD9-deficient egg, even though CD9-deficient eggs are highly refractory to the fusion with sperm. This finding provides strong evidence for the involvement of CD9-containing, fusion-facilitating vesicles in the sperm-egg fusion. Secondly, there are similarities between the generation of retroviruses in the host cells and the formation of small cellular vesicles, termed exosomes, in mammalian cells. The exosomes are involved in intercellular communication through transfer of proteins and ribonucleic acids (RNAs) including mRNAs and microRNAs. These collective studies provide an insight into the molecular mechanism of membrane fusion events.

Increased expression of ADAM33 protein in asthmatic patients as compared to non-asthmatic controls

BACKGROUND & OBJECTIVES

ADAM33 is a member of a family of genes that encode membrane-anchored proteins with a disintegrin and a metalloprotease domain, primarily expressed in lung fibroblasts and bronchial smooth muscle cells. ADAM33 has been identified as a risk factor for asthma and is known as a gene associated with airway remodelling. The present study was conducted with the aims to investigate the expression of ADAM33 protein in patients of asthma and non-asthmatic controls, and to assess if the expression of ADAM33 protein relates with severity of asthma.

METHODS

A total of 35 subjects, including 27 patients with asthma and eight non-asthmatic controls were included using Global Initiative for Asthma guidelines 2005. Bronchial biopsy tissues were collected and paraffin sections were made to store all study samples. Immunohistochemistry was performed using standardized protocol.

RESULTS

An increase in expression of ADAM33 protein was observed in the epithelium, smooth muscle and mesenchymal cells of asthma cases when compared to controls but there was no relationship with severity of asthma.

INTERPRETATION & CONCLUSIONS

A higher expression of ADAM33 protein was seen in asthma patients compared to controls. Large prospective studies need to be done with adequate study design to confirm these preliminary finding.

Molecular cloning, characterization of porcine IZUMO1, an IgSF family member

IZUMO1, belonging to the family of mammalian immunoglobulin proteins, has been well characterized in the mouse. Here, we describe the molecular cloning and expression analysis of porcine IZUMO1 (pIZUMO1). Partial sequence information published in the National Center for Biotechnology Information (NCBI) database was used to generate the full-length sequence for IZUMO1 using rapid amplification of cDNA ends (RACE). A search of the porcine genomic sequence in the NCBI database identified a bacterial artificial chromosome (BAC) encoding the pIZUMO1 gene. This BAC is derived from porcine chromosome 6 and is syntenic with the corresponding regions of mouse, bovine, and human genomes encoding the IZUMO gene family. This BAC was found to encode an IZUMO1 protein with a predicted amino acid sequence having high similarity with mouse and human IZUMO1. Western blot analysis of proteins from porcine tissues indicated that pIZUMO1 was specifically expressed in the sperm. Furthermore, to confirm whether pIZUMO1 forms complexes, we overexpressed pIZUMO1 in HEK293 cells. The recombinant pIZUMO1 from cell extracts was found to form complexes. Our finding suggests that pIZUMO1 forms homodimeric complex on the sperm membrane. Furthermore, an IVF inhibition assay with an antibody for the porcine IZUMO1 Ig-like domain showed that Ig-like domain effectively prevented pig sperm-egg interactions.

Involvement of the prostate and testis expression (PATE)-like proteins in sperm-oocyte interaction

BACKGROUND

The prostate and testis expression (PATE)-like family of proteins are expressed mainly in the male genital tract. They are localized in the sperm head and are homologous to SP-10, the acrosomal vesicle protein also named ACRV1. Our aim was to characterize the expression and functional role of three PATE-like proteins in the testis and ejaculated sperm.

METHODS

The expression and localization of PATE-like proteins in human testis biopsies (n= 95) and sperm cells were assessed by RT-PCR, immunohistochemistry and immunofluorescence staining (at least 600 sperm cells per specimen). The function of the PATE protein was tested by the hemizona assay and hamster egg penetration test (HEPT).

RESULTS

PATE and PATE-M genes and proteins were present almost exclusively in germ cells in the testis: immunoflourescence showed that the percentage of germ cells positive for PATE, PATE-M and PATE-B was 85, 50 and 2%, respectively. PATE and PATE-M proteins were localized in the equatorial segment of the sperm head, while PATE-B protein was localized in the post-acrosomal region. A polyclonal antibody (Ab, at 1:50 and 1:200 dilutions) against the PATE protein did not inhibit sperm-zona binding in the hemizona assay (hemizona index of 89.6 ± 10 and 87 ± 36%, respectively). However, there was inhibition of sperm-oolemma fusion and penetration in the HEPT (penetration index: without Ab 7 ± 3.9; Ab dilution of 1:100, 4 ± 3.5; Ab dilution of 1:20, 0.6 ± 1.2, P < 0.001).

CONCLUSIONS

Our data suggest that PATE protein is involved in sperm-oolemma fusion and penetration but not sperm-zona binding.

Protein disulfide isomerase homolog PDILT is required for quality control of sperm membrane protein ADAM3 and male fertility [corrected]

A disintegrin and metalloproteinase 3 (ADAM3) is a sperm membrane protein critical for both sperm migration from the uterus into the oviduct and sperm primary binding to the zona pellucida (ZP). Here we show that the testis-specific protein disulfide isomerase homolog (PDILT) cooperates with the testis-specific calreticulin-like chaperone, calsperin (CALR3), in the endoplasmic reticulum and plays an indispensable role in the disulfide-bond formation and folding of ADAM3. Pdilt(-/-) mice were male infertile because ADAM3 could not be folded properly and transported to the sperm surface without the PDILT/CALR3 complex. Peculiarly we find that not only Pdilt(-/-), but also Adam3(-/-), spermatozoa effectively fertilize eggs when the eggs are surrounded in cumulus oophorus. These findings reveal that ADAM3 requires testis-specific private chaperones to be folded properly and that the principle role of ADAM3 is for sperm migration into the oviduct but not for the fertilization event. Moreover, the importance of primary sperm ZP binding, which has been thought to be a critical step in mammalian fertilization, should be reconsidered.

Oocyte specific oolemmal SAS1B involved in sperm binding through intra-acrosomal SLLP1 during fertilization

Molecular mechanisms by which fertilization competent acrosome-reacted sperm bind to the oolemma remain uncharacterized. To identify oolemmal binding partner(s) for sperm acrosomal ligands, affinity panning was performed with mouse oocyte lysates using sperm acrosomal protein, SLLP1 as a target. An oocyte specific membrane metalloproteinase, SAS1B (Sperm Acrosomal SLLP1 Binding), was identified as a SLLP1 binding partner. cDNA cloning revealed six SAS1B splice variants, each containing a zinc binding active site and a putative transmembrane domain, with signal peptides in three variants. SAS1B transcripts were ovary specific. SAS1B protein was first detected in early secondary follicles in day 3 ovaries. Immunofluorescence localized SAS1B to the microvillar oolemma of M2 oocytes. After fertilization, SAS1B decreased on the oolemma and became virtually undetectable in blastocysts. In transfected CHO-K1 cells SAS1B localized to the surface of unpermeabilized cells. Recombinant and native SLLP1 co-localized with SAS1B to the microvillar domain of ovulated M2 oocytes. Molecular interactions between mouse SLLP1 and SAS1B were demonstrated by surface plasmon resonance, far-western, yeast two-hybrid, recombinant- and native-co-IP analyses. SAS1B bound to SLLP1 with high affinity. SAS1B had protease activity, and SAS1B protein or antibody significantly inhibited fertilization. SAS1B knockout female mice showed a 34% reduction in fertility. The study identified SAS1B-SLLP1 as a pair of novel sperm-egg binding partners involving the oolemma and intra-acrosomal compartment during fertilization.

Purification of N-acetyllactosamine-binding activity from the porcine sperm membrane: possible involvement of an ADAM complex in the carbohydrate-binding activity of sperm

Although the importance of carbohydrate recognition by sperm during egg zona pellucida binding has been widely reported, the sperm molecular species that recognize the carbohydrates are poorly characterized. Our previous cytochemical study indicated that two kinds of carbohydrate-binding proteins are expressed on porcine sperm heads-one recognizes N-acetyllactosamine (Galβ1-4GlcNAc-), and the other recognizes the Lewis X structure (Galβ1-4(Fucα1-3)GlcNAc-). For this report, we used proteomic techniques to characterize the sperm proteins that bind N-acetyllactosamine. Porcine sperm plasma membrane was solubilized with a detergent solution and subjected to sequential chromatography with dextran sulfate agarose, affinity, and hydroxyapatite, and the binding activities in the eluates were monitored by a solid-phase binding assay. The tryptic peptides of two proteins most likely associated with the binding activities were subjected to tandem mass spectrometry sequencing. A subsequent database search identified one of the two proteins as predicted disintegrin and metalloprotease domain-containing protein 20-like (XP_003128672). The other protein was identified as disintegrin and metalloprotease domain-containing protein 5 (AB613817) by database searches for homologous amino acid sequences, cDNA cloning, nucleotide sequencing and nucleotide database searches. Furthermore, two-dimensional blue native/SDS-PAGE demonstrated that they formed a variety of non-covalent complexes. Therefore, these ADAM complexes probably are responsible for the N-acetyllactosamine-binding activity. An affinity-purified fraction containing these ADAM complexes showed zona pellucida-binding activity, though the activity was relatively weak, and the presence of another zona pellucida-binding protein that probably works in concert with these ADAM complexes was suggested. Immunofluorescence testing suggested that ADAM20-like was localized on the anterior part of the sperm plasma membrane.

Expression, immunolocalization and processing of fertilins ADAM-1 and ADAM-2 in the boar (Sus domesticus) spermatozoa during epididymal maturation

Fertilin alpha (ADAM-1) and beta (ADAM-2) are integral membrane proteins of the ADAM family that form a fertilin complex involved in key steps of the sperm-oocyte membrane interaction. In the present work, we analyzed the presence of ADAM-1 and ADAM-2 mRNAs, the spermatozoa proteins' processing and their sub-cellular localization in epididymal samples from adult boars. ADAM-1 and ADAM-2 mRNAs were highly produced in the testis, but also in the vas efferens and the epididymis. On immunoblots of sperm extracts, ADAM-1 subunit appeared as a main reactive band of ~50-55 kDa corresponding to occurrence of different isoforms throughout the epididymal duct, especially in the corpus region where isoforms ranged from acidic to basic pI. In contrast, ADAM-2 was detected as several bands of ~90 kDa, ~75 kDa, ~50-55 kDa and ~40 kDa. The intensity of high molecular mass bands decreased progressively in the distal corpus where lower bands were also transiently observed, and only the ~40 kDa was observed in the cauda. The presence of bands of different molecular weights likely results from a proteolytic processing occurring mainly in the testis for ADAM-1, and also throughout the caput epididymis for ADAM-2. Immunolocalization showed that fertilin migrates from the acrosomal region to the acrosomal ridge during the sperm transit from the distal corpus to the proximal cauda. This migration is accompanied by an important change in the extractability of a part of ADAM-1 from the sperm membrane. This suggests that the fertilin surface migration may be triggered by the biochemical changes induced by the epididymal post-translational processing of both ADAM1 and ADAM-2. Different patterns of fertilin immunolocalization then define several populations of spermatozoa in the cauda epididymis. Characterization of such fertilin complex maturation patterns is an important step to develop fertility markers based on epididymal maturation of surface membrane proteins in domestic mammals.

The mechanism of sperm-egg interaction and the involvement of IZUMO1 in fusion

An average human ejaculate contains over 100 million sperm, but only a few succeed in accomplishing the journey to an egg by migration through the female reproductive tract. Among these few sperm, only one participates in fertilization. There might be an ingenious molecular mechanism to ensure that the very best sperm fertilize an egg. However, recent gene disruption experiments in mice have revealed that many factors previously described as important for fertilization are largely dispensable. One could argue that the fertilization mechanism is made robust against gene disruptions. However, this is not likely, as there are already six different gene-disrupted mouse lines (Calmegin, Adam1a, Adam2, Adam3, Ace and Pgap1), all of which result in male sterility. The sperm from these animals are known to have defective zona-binding ability and at the same time lose oviduct-migrating ability. Concerning sperm-zona binding, the widely accepted involvement of sugar moiety on zona pellucida 3 (ZP3) is indicated to be dispensable by gene disruption experiments. Thus, the landscape of the mechanism of fertilization is revolving considerably. In the sperm-egg fusion process, CD9 on egg and IZUMO1 on sperm have emerged as essential factors. This review focuses on the mechanism of fertilization elucidated by gene-manipulated animals.

The glycoprotein B disintegrin-like domain binds beta 1 integrin to mediate cytomegalovirus entry

Cellular integrins were identified as human cytomegalovirus (HCMV) entry receptors and signaling mediators in both fibroblasts and endothelial cells. The goal of these studies was to determine the mechanism by which HCMV binds to cellular integrins to mediate virus entry. HCMV envelope glycoprotein B (gB) has sequence similarity to the integrin-binding disintegrin-like domain found in the ADAM (a disintegrin and metalloprotease) family of proteins. To test the ability of this region to bind to cellular integrins, we generated a recombinant soluble version of the gB disintegrin-like domain (gB-DLD). The gB-DLD protein bound to human fibroblasts in a specific, dose-dependent and saturable manner that required the expression of an intact beta1 integrin ectodomain. Furthermore, a physical association between gB-DLD and beta1 integrin was demonstrated through in vitro pull-down assays. The function of this interaction was shown by the ability of cell-bound gB-DLD to efficiently block HCMV entry and the infectivity of multiple in vivo target cells. Additionally, rabbit polyclonal antibodies raised against gB-DLD neutralized HCMV infection. Mimicry of the ADAM family disintegrin-like domain by HCMV gB represents a novel mechanism for integrin engagement by a virus and reveals a unique therapeutic target for HCMV neutralization. The strong conservation of the DLD across beta- and gammaherpesviruses suggests that integrin recognition and utilization may be a more broadly conserved feature throughout the Herpesviridae.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 2: changes in spermatid organelles associated with development of spermatozoa

Spermiogenesis is a long process whereby haploid spermatids derived from the meiotic divisions of spermatocytes undergo metamorphosis into spermatozoa. It is subdivided into distinct steps with 19 being identified in rats, 16 in mouse and 8 in humans. Spermiogenesis extends over 22.7 days in rats and 21.6 days in humans. In this part, we review several key events that take place during the development of spermatids from a structural and functional point of view. During early spermiogenesis, the Golgi apparatus forms the acrosome, a lysosome-like membrane bound organelle involved in fertilization. The endoplasmic reticulum undergoes several topographical and structural modifications including the formation of the radial body and annulate lamellae. The chromatoid body is fully developed and undergoes structural and functional modifications at this time. It is suspected to be involved in RNA storing and processing. The shape of the spermatid head undergoes extensive structural changes that are species-specific, and the nuclear chromatin becomes compacted to accommodate the stream-lined appearance of the sperm head. Microtubules become organized to form a curtain or manchette that associates with spermatids at specific steps of their development. It is involved in maintenance of the sperm head shape and trafficking of proteins in the spermatid cytoplasm. During spermiogenesis, many genes/proteins have been implicated in the diverse dynamic events occurring at this time of development of germ cells and the absence of some of these have been shown to result in subfertility or infertility.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 3: developmental changes in spermatid flagellum and cytoplasmic droplet and interaction of sperm with the zona pellucida and egg plasma membrane

Spermiogenesis constitutes the steps involved in the metamorphosis of spermatids into spermatozoa. It involves modification of several organelles in addition to the formation of several structures including the flagellum and cytoplasmic droplet. The flagellum is composed of a neck region and middle, principal, and end pieces. The axoneme composed of nine outer microtubular doublets circularly arranged to form a cylinder around a central pair of microtubules is present throughout the flagellum. The middle and principal pieces each contain specific components such as the mitochondrial sheath and fibrous sheath, respectively, while outer dense fibers are common to both. A plethora of proteins are constituents of each of these structures, with each playing key roles in functions related to the fertility of spermatozoa. At the end of spermiogenesis, a portion of spermatid cytoplasm remains associated with the released spermatozoa, referred to as the cytoplasmic droplet. The latter has as its main feature Golgi saccules, which appear to modify the plasma membrane of spermatozoa as they move down the epididymal duct and hence may be partly involved in male gamete maturation. The end product of spermatogenesis is highly streamlined and motile spermatozoa having a condensed nucleus equipped with an acrosome. Spermatozoa move through the female reproductive tract and eventually penetrate the zona pellucida and bind to the egg plasma membrane. Many proteins have been implicated in the process of fertilization as well as a plethora of proteins involved in the development of spermatids and sperm, and these are high lighted in this review.

Multivariate analysis of male reproductive function in Inpp5b-/- mice reveals heterogeneity in defects in fertility, sperm-egg membrane interaction and proteolytic cleavage of sperm ADAMs

Past work indicated that sperm from mice deficient in the inositol polyphosphate 5-phosphatase Inpp5b have reduced ability to fertilize eggs in vitro and reduced epididymal proteolytic processing of the sperm protein A Disintegrin and A Metalloprotease 2 (ADAM2). On the basis of these data, our central working hypothesis was that reduced ADAM cleavage would correlate with reduced sperm-egg binding and fusion and in turn with reduced male fertility in Inpp5b(-/-) mice. Multiple endpoints of reproductive functions [mating trials, in vitro fertilization (IVF) assays and ADAM2 and ADAM3 cleavage] were investigated on a male-by-male basis, with pair-wise correlation analysis used to assess the relationships between these various parameters. Motile sperm from Inpp5b(-/-) mice showed significantly reduced fertilization of zona pellucida-free eggs due to reduced binding to the egg plasma membrane and subsequent fusion. Localization of a mouse sperm protein required for gamete fusion, IZUMO1, appears normal in Inpp5b-null sperm. To our surprise and differing from previous reports, we found that ADAM cleavage was only modestly impaired in numerous Inpp5b-null males and varied between individual animals. Performance in mating trials also differed from past reports. The pair-wise correlation analysis revealed that ADAM2 and ADAM3 cleavage was positively correlated, suggesting that processing of these proteins occurs by related/identical mechanisms, but otherwise, there were few correlations between the reproductive endpoints examined here. Nevertheless, this work provides detailed analysis of the Inpp5b(-/-) phenotype and also a blueprint for multivariate analysis to examine relationships between molecular characteristics and in vitro and in vivo physiological functions.

Beta1 integrin is an adhesion protein for sperm binding to eggs

We investigated the role of beta(1) integrin in mammalian fertilization and the mode of inhibition of fertilinbeta-derived polymers. We determined that polymers displaying the Glu-Cys-Asp peptide from the fertilinbeta disintegrin domain mediate inhibition of mammalian fertilization through a beta(1) integrin receptor on the egg surface. Inhibition of fertilization is a consequence of competition with sperm binding to the cell surface, not activation of an egg-signaling pathway. The presence of the beta(1) integrin on the egg surface increases the rate of sperm attachment but does not alter the total number of sperm that can attach or fuse to the egg. We conclude that the presence of beta(1) integrin enhances the initial adhesion of sperm to the egg plasma membrane and that subsequent attachment and fusion are mediated by additional egg and sperm proteins present in the beta(1) integrin complex. Therefore, the mechanisms by which sperm fertilize wild-type and beta(1) knockout eggs are different.

Polymeric ADAM protein mimics interrogate mammalian sperm-egg binding

The sperm proteins ADAM2 and ADAM3, members of the ADAM family of proteins, have been implicated in mammalian sperm-egg binding. However, elucidating their roles is complex because of the interdependence of ADAM protein expression in the testis. Hence, multivalent probes containing the three-amino acid binding sequence of ADAM2, glutamate-cysteine-aspartate (ECD), and ADAM3, glutamine-cysteine-aspartate (QCD), were designed, synthesized, and tested to investigate gamete interactions. In this work, ECD polymer mimics were synthesized by ring-opening metathesis polymerization with a faster initiating ruthenium catalyst than previously used. Polymers containing 100 copies of the ECD peptide mimic were found to be the best inhibitors of fertilization. The multivalent QCD polymers were also tested as inhibitors of fertilization. The structure-activity profile was the same as ECD polymers, but the overall potency was lower. Both ECD and QCD polymers require the presence of beta(1) integrin to inhibit fertilization. Next, triblock ABA and ABC copolymers containing both ECD and QCD ligands were synthesized with 96 monomer spacers as their B blocks. Although these polymers had lower densities of ECD and QCD peptides, their potencies correlated with the potencies of their corresponding homopolymers. In addition, no synergy between ECD and QCD mimics was observed. All the data suggest that QCD and ECD bind to the same complex of proteins that includes beta(1) integrin.

Comprehensive analysis of reproductive ADAMs: relationship of ADAM4 and ADAM6 with an ADAM complex required for fertilization in mice

A Disintegrin And Metalloprotease (ADAM) family members expressed in male reproductive tissues are divided phylogenetically into three major groups. In the present study, we analyzed six ADAMs in one of the groups (ADAMs 4, 6, 24, 26, 29, and 30) of which function is largely unknown. Our results showed that most of the ADAMs undergo unique processing during sperm maturation and are located at the surface of sperm head. We found that the levels of ADAM4 and ADAM6 are dramatically reduced in Adam2 and Adam3 knockout sperm defective in various fertilization processes. We observed premature processing of ADAM4 in the Adam3-null mice. Furthermore, we obtained a result showing complex formation of ADAM6 with ADAM2 and ADAM3 in testis. Taken together, these results disclose involvement of ADAM4 and ADAM6 in a reproductive ADAM system that functions in fertilization.

Importance of the porcine ADAM3 disintegrin domain in sperm-egg interaction

In the mouse, ADAM3, a well-characterized testis-specific protein of the A disintegrin and metalloprotease (ADAM) family, has a crucial role in fertilization by mediating sperm binding to the egg zona pellucida. However, little is known about ADAM3 in other species, such as domestic pigs. We have identified porcine ADAM3 and analyzed the protein. RT-PCR and trypsinization of sperm surface proteins revealed that porcine ADAM3 is expressed at high levels in the testis and on the sperm surface. Furthermore, an IVF inhibition assay with a recombinant porcine ADAM3 disintegrin domain showed that treatment of the disintegrin domain effectively prevented pig sperm-egg interactions. In the present study, we demonstrated the presence of ADAM3a and ADAM3b molecules in the pig and examined their roles in fertilization.

Characterization of a novel, testis-specific equine serine/threonine kinase

Testis-specific protein kinases are important because of their potential role in spermiogenesis, sperm maturation, and sperm function. In the present study, a novel serine-threonine kinase with high identity to human serine-threonine kinase 31 (STK31) was cloned from equine testis and expression of the protein was characterized in equine testis and ejaculated spermatozoa. Five over-lapping independent clones were plaque purified after screening of a lambda ZAP cDNA expression library constructed from equine testis. Sequence analysis and alignment of all five clones showed high identity with human STK31 with approximately 200 bp of the equine N-terminal sequence incomplete. The putative full-length coding sequence of this testis specific equine cDNA was completed by amplification of a 200-bp fragment using a human primer upstream of the reported translational start site with equine specific nested primers. Northern blot analysis using the equine STK31 cDNA detected an RNA transcript of approximately 3.1 kb present in testis but not in other reproductive or somatic tissues. Immunolocalization of the protein in equine testis and spermatozoa demonstrated that STK31 was present in post-meiotic germ cells with localization to the equatorial segment of testicular spermatozoa. Analysis of the domain structure of equine STK31 revealed a protein kinase domain along with a putative RNA-binding region. The post-meiotic expression of this protein along with its domain structure suggests that STK31 may have a role in reorganization of sperm chromatin during spermiogenesis. The cloning of this novel, testis-specific equine STK provides a new tool to explore the role of kinases in sperm function.

Equatorial segment protein (ESP) is a human alloantigen involved in sperm-egg binding and fusion

The equatorial segment of the sperm head is known to play a role in fertilization; however, the specific sperm molecules contributing to the integrity of the equatorial segment and in binding and fusion at the oolemma remain incomplete. Moreover, identification of molecular mediators of fertilization that are also immunogenic in humans is predicted to advance both the diagnosis and treatment of immune infertility. We previously reported the cloning of Equatorial Segment Protein (ESP), a protein localized to the equatorial segment of ejaculated human sperm. ESP is a biomarker for a subcompartment of the acrosomal matrix that can be traced through all stages of acrosome biogenesis (Wolkowicz et al, 2003). In the present study, ESP immunoreacted on Western blots with 4 (27%) of 15 antisperm antibody (ASA)-positive serum samples from infertile male patients and 2 (40%) of 5 ASA-positive female sera. Immunofluorescent studies revealed ESP in the equatorial segment of 89% of acrosome-reacted sperm. ESP persisted as a defined equatorial segment band on 100% of sperm tightly bound to the oolemma of hamster eggs. Antisera to recombinant human ESP inhibited both oolemmal binding and fusion of human sperm in the hamster egg penetration assay. The results indicate that ESP is a human alloantigen involved in sperm-egg binding and fusion. Defined recombinant sperm immunogens, such as ESP, may offer opportunities for differential diagnosis of immune infertility.

Emerging roles of ADAM and ADAMTS metalloproteinases in cancer

A disintegrin and metalloproteinases (ADAMs) are a recently discovered family of proteins that share the metalloproteinase domain with matrix metalloproteinases (MMPs). Among this family, structural features distinguish the membrane-anchored ADAMs and the secreted ADAMs with thrombospondin motifs referred to as ADAMTSs. By acting on a large panel of membrane-associated and extracellular substrates, they control several cell functions such as adhesion, fusion, migration and proliferation. The current review addresses the contribution of these proteinases in the positive and negative regulation of cancer progression as mainly mediated by the regulation of growth factor activities and integrin functions.