Molecular characterization of a hamster oviduct-specific glycoprotein

The fluid factor OVGP1 provides a significant oviductal microenvironment for the reproductive process in golden hamster†

The mammalian oviductal lumen is a specialized chamber that provides an environment that strictly regulates fertilization and early embryogenesis, but the regulatory mechanisms to gametes and zygotes are unclear. We evaluated the oviductal regulation of early embryonic development using Ovgp1 (encoding an oviductal humoral factor, OVGP1)-knockout golden hamsters. The experimental results revealed the following: (1) female Ovgp1-knockout hamsters failed to produce litters; (2) in the oviducts of Ovgp1-knockout animals, fertilized eggs were sometimes identified, but their morphology showed abnormal features; (3) the number of implantations in the Ovgp1-knockout females was low; (4) even if implantations occurred, the embryos developed abnormally and eventually died; and (5) Ovgp1-knockout female ovaries transferred to wild-type females resulted in the production of Ovgp1-knockout egg-derived OVGP1-null litters, but the reverse experiment did not. These results suggest that OVGP1-mediated physiological events are crucial for reproductive process in vivo, from fertilization to early embryonic development. This animal model shows that the fate of the zygote is determined not only genetically, but also by the surrounding oviductal microenvironment.

The role of oviduct-specific glycoprotein (OVGP1) in modulating biological functions of gametes and embryos

Diverse lines of evidence indicate that the mammalian oviduct makes important contributions to the complex process of reproduction other than being simply a conduit for the transport of gametes and embryos. The cumulative synthesis and transport of proteins secreted by oviductal secretory cells into the oviductal lumen create a microenvironment supporting important reproductive events, including sperm capacitation, fertilization, and early embryo development. Among the components that have been identified in the oviductal fluid is a family of glycosylated proteins known collectively as oviduct-specific glycoprotein (OVGP1) or oviductin. OVGP1 has been identified in several mammalian species, including humans. The present review summarizes the work carried out, in various mammalian species, by many research groups revealing the synthesis and secretion of OVGP1, its fate in the female reproductive tract upon secretion by the oviductal epithelium, and its role in modulating biological functions of gametes and embryos. The production and functions of recombinant human OVGP1 and recombinant OVGP1 of other mammalian species are also discussed. Some of the findings obtained with immunocytochemistry will be highlighted in the present review. It is hoped that the findings obtained from recent studies carried out with recombinant OVGP1 from various species will rekindle researchers’ interest in pursuing further the role of the oviductal microenvironment, of which OVGP1 is a major component, in contributing to the successful occurrence of early reproductive events, and the potential use of OVGP1 in improving the current assisted reproductive technology in alleviating infertility.

A Comparative View on the Oviductal Environment during the Periconception Period

The oviduct plays important roles in reproductive events: sperm reservoir formation, final gamete maturation, fertilization and early embryo development. It is well known that the oviductal environment affects gametes and embryos and, ultimately, the health of offspring, so that in vivo embryos are better in terms of morphology, cryotolerance, pregnancy rates or epigenetic profile than those obtained in vitro. The deciphering of embryo-maternal interaction in the oviduct may provide a better understanding of the embryo needs during the periconception period to improve reproductive efficiency. Here, we perform a comparative analysis among species of oviductal gene expression related to embryonic development during its journey through the oviduct, as described to date. Cross-talk communication between the oviduct environment and embryo will be studied by analyses of the secreted or exosomal proteins of the oviduct and the presence of receptors in the membrane of the embryo blastomeres. Finally, we review the data that are available to date on the expression and characterization of the most abundant protein in the oviduct, oviductin (OVGP1), highlighting its fundamental role in fertilization and embryonic development.

Porcine oviductal extracellular vesicles interact with gametes and regulate sperm motility and survival

Once in the female reproductive tract, spermatozoa undergo several modifications to acquire their complete fertilizing ability. Interactions between the oviductal fluid (OF) and gametes contribute to a successful fertilization. Recently, oviductal extracellular vesicles have been identified as an important part of the OF but their interactions with gametes are not fully understood. In the present study, we aim at determining the patterns of interactions between porcine oviductal extracellular vesicles (poEVs) and gametes (spermatozoa and oocytes). Moreover, we evaluate the effect of poEVs on sperm survival and motility to better understand the mechanisms by which poEVs modulate the processes leading to fertilization. Evaluation of poEVs uptake by spermatozoa showed that poEVs bind to spermatozoa in a time and dose dependent manner. Co-incubation of spermatozoa with poEVs (0.2 μg/μL) increased fresh and frozen sperm survival after 6 and 17 h, respectively. By contrast, poEVs supplementation reduced the total and progressive sperm motility after 2 h. Additionally, we demonstrated that poEVs interacted with the cumulus cells, zona pellucida (ZP) and oocyte, being able to cross the ZP. Besides, we showed that poEVs delivered their cargo into the oocyte, by the transfer of OVGP1 protein. In conclusion, our results demonstrated that poEVs are able to interact with both gametes. Besides, the findings from the present study showed that poEVs may participate in maintaining sperm viability and reducing motility, functions associated with the oviduct sperm reservoir. Although further investigations are needed, our results indicate that poEVs can be a potential tool to improve sperm life span during sperm handling and enhance IVF outcomes.

Structural and functional characterization of buffalo oviduct-specific glycoprotein (OVGP1) expressed during estrous cycle

Oviduct-specific glycoprotein (OVGP1) is a high molecular weight chitinase-like protein belonging to GH18 family. It is secreted by non-ciliated epithelial cells of oviduct during estrous cycle providing an essential milieu for fertilization and embryo development. The present study reports the characterization of buffalo OVGP1 through structural modeling, carbohydrate-binding properties and evolutionary analysis. Structural model displayed the typical fold of GH18 family members till the boundary of chitinase-like domain further consisting of a large (β/α)8 TIM barrel sub-domain and a small (α+β) sub-domain. Two critical catalytic residues were found substituted in the catalytic centre (Asp to Phe118, Glu to Leu120) compared with the active chitinase. The carbohydrate-binding groove in TIM barrel was lined with various conserved aromatic residues. Molecular docking with different sugars revealed the involvement of various residues in hydrogen-bonding and non-bonded contacts. Most of the substrate-binding residues were conserved except for a few replacements (Ser13, Lys48, Asp49, Pro50, Asp167, Glu199, Gln272 and Phe275) in comparison with other GH18 members. The residues Trp10, Trp79, Asn80, Gln272, Phe275 and Trp334 were involved in recognition of all six ligands. The α+β sub-domain participated in sugar-binding through Thr270, Gln272, Tyr242 and Phe275. The binding assays revealed significant sugar-binding with purified native and recombinant OVGP1. Phylogenetic analysis revealed that OVGP1 was closely related to AMCases followed by other CLPs and evolution of OVGP1 occurred through several gene duplications. This is the first study describing the structural characteristics of OVGP1 that will further help to understand its interaction with gametes to perform crucial reproductive functions.

Recombinant hamster oviductin is biologically active and exerts positive effects on sperm functions and sperm-oocyte binding

Studies carried out in several mammalian species suggest that oviductin, also known as oviduct-specific glycoprotein or OVGP1, plays a key role in sperm capacitation, fertilization, and development of early embryos. In the present study, we used recombinant DNA technology to produce, for the first time, recombinant hamster OVGP1 (rHamOVGP1) in human embryonic kidney 293 (HEK293) cells. rHamOVGP1 secreted in the culture medium was purified by affinity chromatography. The resulting protein migrated as a poly-dispersed band of 160-350 kDa on SDS-PAGE corresponding to the molecular mass of the native HamOVGP1. Subsequent mass spectrometric analysis of the purified rHamOVGP1 confirmed its identity as HamOVGP1. Immunocytochemistry demonstrated binding of rHamOVGP1 to the mid-piece and head of hamster sperm and to the zona pellucida (ZP) of ovarian oocytes. In vitro functional experiments showed that addition of rHamOVGP1 in the capacitation medium further enhanced tyrosine phosphorylation of two sperm proteins of approximately 75 kDa and 83 kDa in a time-dependent manner. After 3 hours of incubation in the presence of rHamOVGP1, a significant increase in acrosome reaction was measured. Pretreatment of either sperm or oocyte with 20 μg/ml of rHamOVGP1 prior to sperm-egg binding assay significantly increased the number of sperm bound to the ZP. Addition of rHamOVGP1 in the medium during sperm-egg binding with either oocyte or sperm pretreated with rHamOVGP1 also saw an increase in the number of sperm bound to ZP. In all experimental conditions, the effect of rHamOVGP1 on sperm-oocyte binding was negated by the addition of monoclonal anti-HamOVGP1 antibody. The successful production and purification of a biologically active rHamOVGP1 will allow further exploration of the function of this glycoprotein in reproductive function.

Structures and biosynthesis of the N- and O-glycans of recombinant human oviduct-specific glycoprotein expressed in human embryonic kidney cells

Oviduct-specific glycoprotein (OVGP1) is a major mucin-like glycoprotein synthesized and secreted exclusively by non-ciliated secretory cells of mammalian oviduct. In vitro functional studies showed that OVGP1 plays important roles during fertilization and early embryo development. We have recently produced recombinant human oviduct-specific glycoprotein (rhOVGP1) in human embryonic kidney 293 (HEK293) cells. The present study was undertaken to characterize the structures and determine the biosynthetic pathways of the N- and O-glycans of rhOVGP1. Treatment of the stable rhOVGP1-expressing HEK293 cells with either GalNAcα-Bn to block O-glycan extension, tunicamycin to block N-glycosylation, or neuraminidase increased the electrophoretic mobility of rhOVGP1. A detailed analysis of O- and N-linked glycans of rhOVGP1 by mass spectrometry showed a broad range of many simple and complex glycan structures. In order to identify the enzymes involved in the glycosylation of rhOVGP1, we assayed glycosyltransferase activities involved in the assembly of O- and N-glycans in HEK293 cells, and compared these to those from the immortalized human oviductal cells (OE-E6/E7). Our results demonstrate that HEK293 and OE-E6/E7 cells exhibit a similar spectrum of glycosyltransferase activities that can synthesize elongated and sialylated O-glycans with core 1 and 2 structures, as well as complex multiantennary N-glycans. It is anticipated that the knowledge gained from the present study will facilitate future studies of the role of the glycans of human OVGP1 in fertilization and early embryo development.

Sequence analysis of feline oviductin and its expression during the estrous cycle in the domestic cat (Felis catus)

Oviductins belong to a family of oviduct-specific glycoproteins believed to play an important role in fertilization and/or early embryonic development. Oviductin cDNA between species is highly conserved and shares 58% to 98% similarity in the deduced amino acid sequences. Our objective in this study was to sequence the full open reading frame of the feline oviductin and to examine its expression during the estrous cycle on both mRNA and protein level. The obtained cDNA containing the full open reading frame was determined to be 1677 nucleotides coding for a deduced protein of 558 amino acids. Identities between species range from 74% (mouse) to 80% (human, baboon, and rhesus) within the N-terminal protein region. Major differences were localized in the carboxy terminal region, which corresponds to exon 11 of the gene. Feline oviductin contained one putative N-linked glycosylation site, six O-linked glycosylation sites, a potential heparin binding site, and two cholesterol recognition and/or interaction amino acid consensus (CRAC) domains. Oviductin expression was analyzed by real time quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry. Both approaches revealed an estrous cycle-dependent expression in the ampulla and isthmus. Quantitative PCR showed highest oviductin mRNA copy numbers in the early and late follicular stage and reduced mRNA expression during all other stages. With the exception of the early follicular stage, feline oviductin mRNA abundance was not significantly different in the oviductal segments ampulla and isthmus. A prominent immunolabeling was seen in the early and late follicular stage which disappeared after ovulation, indicating a function of the protein during sperm storage and fertilization.

Molecular characterization and expression of dipeptidase 3, a testis-specific membrane-bound dipeptidase: complex formation with TEX101, a germ-cell-specific antigen in the mouse testis

We previously established an anti-sperm head auto-monoclonal antibody designated Ts4. The immunoreactivity of this antibody was also observed in other reproduction-related cells, such as testicular germ cells and early embryos, suggesting that the Ts4-recognized molecules might play a role in the reproductive process. However, the molecular characteristics and functions of the antigens warrant further clarification. In this study, we primarily attempted identification of the mAb-recognized molecules within the mouse testis. An immunoprecipitation method, together with liquid chromatography-tandem mass spectrometry, revealed that the testicular immunoprecipitants with Ts4 contained dipeptidase 3 (DPEP3), a member of the membrane-bound dipeptidase family. A Western blot analysis using an anti-DPEP3 polyclonal antibody established in this study showed that this molecule was glycosylated and formed a disulfide-linked homodimer within the testis. Expression of DPEP3 protein was observed in the testicular germ cells, but not in the Sertoli or interstitial cells, or in any other major organs. Although Western blot analysis of testicular proteins separated by two-dimensional SDS-PAGE failed to demonstrate binding of Ts4 to DPEP3, we found that DPEP3 forms complexes with Ts4-immunoreactive molecules, such as TEX101, on the surfaces of spermatocytes, spermatids, and testicular spermatozoa. Based on data showing in the present study, further studies concerning DPEP3 on the testicular germ cells may help to clarify the molecular mechanisms of testicular germ-cell development.

Purification, sequence characterization and effect of goat oviduct-specific glycoprotein on in vitro embryo development

Oviduct-specific glycoprotein (oviductin) plays an important role during fertilization and early embryonic development. The oviductin cDNA was successfully cloned and sequenced in goat, which possessed an open reading frame of 1620 nucleotides representing 539 amino acids. Predicted amino acid sequence showed very high identity with sheep (97%) followed by cow (94%), porcine (77%), hamster (69%), human (66%), rabbit (65%), mouse (64%) and baboon (62%). The bioinformatics analysis of the sequences revealed the presence of a signal sequence of 21 amino acids, one potential N-linked glycosylation site at position 402, 21 potential O-linked glycosylation sites and 36 potential phosphorylation sites. The native oviductin was purified from the oviductal tissue, which showed three distinct bands on SDS-PAGE and western blot (MW ~60-95 kDa). The predicted molecular weight of goat oviductin was 57.5 kDa, calculated from the amino acid sequences. The observed higher molecular weight has been attributed to the presence of large number of potential O-linked glycosylation sites. The lower concentration (10 μg/mL) of oviductin increased the cleavage rate, morula and blastocyst yield significantly (P < 0.05) as compared to higher concentration (100 μg/mL). Goat oviductin retarded the activity of pronase (0.1%) on zona solubility of oocytes significantly (P < 0.01).

Oviductal secretions: will they be key factors for the future ARTs?

A variety of evolutionary processes has led to the development of different organs to ensure that internal fertilization occur successfully. Fallopian tubes are a particularly interesting example of such organs. Some of the key events during fertilization and early embryo development occur in the oviduct. Knowledge of the different components described in the oviduct is extensive. Oviductal components include hormones, growth factors and their receptors that have important roles in the physiology of the oviduct and embryo development. Other oviductal factors protect the gamete and the embryos against oxidative stress and pathogens. Different proteins and enzymes are present in the oviductal fluid and have the ability to interact with the oocyte and the sperm before the fertilization occurs. Of special interest is the oviduct-specific glycoprotein (OVGP1), a glycoprotein that is conserved in different mammals, and its association with the zona pellucida (ZP). Interaction of the oocyte with oviductal secretions leads us to emphasize the concept of 'ZP maturation' within the oviduct. The ZP changes produced in the oviduct result in an increased efficiency of the in vitro fertilization technique in some animal models, contributing in particular to the control of polyspermy and suggesting that a similar role could be played by oviductal factors in human beings. Finally, attention should be given to the presence in the oviductal fluid of several embryotrophic factors and their importance in relation to the in vivo versus in vitro developmental ability of the embryos.

Molecular cloning and characterization of rat chitotriosidase

Recent year some members of mammalian chitinases and chitinase-like proteins have been discovered, but rat counterpart of human and mouse chitotriosidase has not been identified. Moreover, the physiological functions of mammalian chitinases are not very clear. To facilitate the studies we cloned the cDNA encodes the rat chitotriosidase. The results revealed that it is differ from mouse and human chitotriosidase genes, it exist alternative splicing transcripts in several tissues we detected due to different transcriptional initiation sites and different exon usage, although all the open reading frame of these cDNAs predict a protein of 464 amino acids with a typical chitinase structure, including a signal peptide, a highly conserved catalytical domain and a chitin-binding structure. The predicted amino acid sequence is highly homologous to that of mouse and human chitotriosidase. Recombinant expression of the cloned cDNA demonstrated that the encoded protein is secreted extracellularly and has chitinolytic activity.

Molecular diversity of TEX101, a marker glycoprotein for germ cells monitored with monoclonal antibodies: variety of the molecular characteristics according to subcellular localization within the mouse testis

TEX101 was characterized as a unique germ cell marker molecule using the specific monoclonal antibody (mAb), TES101. Although this mAb has strong affinity/specificity for TEX101, TES101 mAb loses its reactivity under reducing conditions. In this study, we have generated new mAbs against TEX101 to compensate for the shortcomings of the TES101 mAb using different approaches. First, we immunized mice with the antigen on a baculovirus expression system and isolated new anti-TEX101 mAbs, 6002 and 6035. Second, we raised the mAb Ts4 from spleen cells of an immunologically naive old mouse. Western blot analysis revealed that the new mAbs possess immunoreactivity under reducing/non-reducing conditions. Immunopositive staining of the mAbs against Bouin-fixed sections was observed in spermatocytes, spermatids and testicular spermatozoa, but not in other cells, similar to paraformaldehyde (PFA)-fixed frozen sections stained with TES101 as previously reported. However, whereas the mAbs 6002/6035 mainly showed immunoreactivity only in spermatocytes in PFA-fixed frozen sections, the reactivity of the mAbs to spermatids and testicular spermatozoa was clearly recovered when the PFA-fixed sections were autoclaved or treated with SDS. Peptide mapping and deglycosylation analysis indicated that the epitopes for TES101, 6002 and 6035 are located within TEX101(25-94), whereas Ts4 recognized N-linked carbohydrate moieties on TEX101 in Triton X-100-soluble mouse testicular extracts but not in the extracellular or water-soluble fractions. These results suggest strongly that the molecular association or structure of N-linked carbohydrate moieties of TEX101 varies according to its subcellular localization within the seminiferous tubules. These new mAbs will be valuable tools for further analysis of TEX101, including its function(s).

TEX101, a germ cell-marker glycoprotein, is associated with lymphocyte antigen 6 complex locus k within the mouse testis

In adult male mice, the glycosylphosphatidyl inositol-anchored glycoprotein TEX101 is expressed only in germ cells and is thought to be involved in spermatogenesis. However, the details regarding the function of TEX101 remain to be clarified. We previously identified Ly6k as a candidate TEX101-associated protein, but as molecular probes are not currently available to detect Ly6k, we do not have conclusive evidence of the association between TEX101 and Ly6k. In this study, we confirmed the biological interaction between TEX101 and Ly6k using an established anti-mouse Ly6k polyclonal antibody (pAb). A combination of immunoprecipitation, Western blot, and immunohistochemical analyses using the pAb revealed that TEX101 is physically associated with Ly6k within the testis. In addition, these proteins simultaneously co-migrate into the detergent-resistant membrane fractions, suggesting that TEX101 collaborates with Ly6k on the cell membrane and may play a role in spermatogenesis.

Inhibition of cell spreading in CHO cells transfected with cDNA of a glycosylphosphatidyl inositol-anchored protein, GPI-80

We have previously cloned a glycosylphosphatidyl inositol (GPI)-anchored protein, designated GPI-80 that associated with integrin and may modulate leukocyte adherence and migration. Recent studies have shown that GPI-80 belongs to a Vanin family that is related to pantetheinase, but the regulatory function of GPI-80 in cell adherence is still unclear. To clarify the possible functions of GPI-80, we transfected GPI-80 cDNA into Chinese hamster ovary (CHO) cells and observed adherence and morphological changes. Adherence of GPI-80 transfectants was significantly decreased when signal strength for the cell adhesion is weak, and the cell spreading of the transfectants was strongly inhibited. This inhibitory effect of GPI-80 expression was largely canceled by GPI-80 shedding with phosphatidy-linositol-specific phospholipase C. Interestingly, spreading of GPI-80 transfectants was temporarily recovered from the round shape but not maintained by stimulation with known activators of beta1 integrins, phorbol myristate acetate and manganese ions. Taken together, these results suggest that the expression of GPI-80 on CHO cells can influence cell spreading in weak adhesive signal conditions via extracellular matrix molecules.

Detection of nascent and/or mature forms of oviductin in the female reproductive tract and post-ovulatory oocytes by use of a polyclonal antibody against recombinant hamster oviductin

Oviductins belong to a family of glycoproteins that have been suggested to play several roles during the early processes of reproduction. Recently, a polyclonal antibody was raised against recombinant hamster oviductin (rhaOv(m)). Here the anti-rhaOv(m) antibody was used to investigate the sites of localization of oviductin in the female golden hamster. In the hamster oviduct, immunolabeling was restricted to the content of the Golgi saccules and secretory granules of the non-ciliated oviduct cells. After its release into the lumen, oviductin becomes associated with the zona pellucida of post-ovulatory oocytes. In unfertilized oocytes, oviductin was also detected in membrane invaginations along the oolemma and in some vesicles within the ooplasm. Furthermore, oviductin was detected over the microvilli and within multivesicular bodies of uterine epithelial cells. Western blotting analysis revealed the presence of oviductin in the hamster oviduct but not in the uterus or ovary. In the oviduct, the anti-rhaOv(m) antibody detected a polydispersed band corresponding to native oviductin (160-350 kD) and several lower molecular weight bands (<100 kD) corresponding to nascent and partially glycosylated forms of oviductin. The anti-rhaOv(m) antibody provides an additional tool for investigation into the cytochemical and biochemical properties of different forms of hamster oviductin in the female reproductive tract.

Evidence for the Regulation of Glycosylation of Golden Hamster (Mesocricetus auratus) Oviductin During the Estrous Cycle1

The oviduct contributes to the reproductive environment by secreting various factors, including a family of glycoproteins termed oviductins. Although many studies have demonstrated that ovarian hormones modulate oviductin gene expression in several mammalian species, there has been controversy surrounding the regulation of golden hamster oviductin. The current study was undertaken to investigate the transcriptional and translational modifications of hamster oviductin during the estrous cycle. First, we verified that hamster oviductin mRNA expression remains constant throughout the estrous cycle by semiquantitative reverse transcription polymerase chain reaction. We then developed a polyclonal antibody against recombinant hamster oviductin (rhaOvm). The anti-rhaOvm antibody was subsequently used in conjunction with quantitative immunocytochemistry to investigate the oviductin levels in the hamster oviduct during the estrous cycle. Quantification of immunolabeling revealed a high, consistent level of glycoprotein throughout the estrous cycle. Therefore, it appears that the production of oviductin is not regulated differentially during the estrous cycle. Size variations in hamster oviductin expression were also investigated by Western blot analysis. The oviduct contains several forms of oviductin at each stage of the estrous cycle, the native glycosylated form(s) of 160-350 kDa, and several precursor forms of 70-100 kDa. Although variations in the intensities of the polydispersed band were not evident during the estrous cycle, additional bands ranging from 90 to 100 kDa were detected in the estrus, metestrus, and diestrus 1 stages. The results from the present investigations suggest that whereas ovarian hormones do not appear to influence the hamster oviductin mRNA and protein expressions, glycosylation of hamster oviductin appears to be differentially regulated during the estrous cycle.

Oviduct-specific glycoprotein modulates sperm-zona binding and improves efficiency of porcine fertilization in vitro

Oviduct-specific glycoprotein (OGP) displays estrus-associated regional and temporal differences in expression and localizes to the zona pellucida, perivitelline space, and plasma membrane of oviductal oocytes and embryos, suggesting that it may have a role in regulation of fertilization and/or early embryonic development. The aims of this study were to evaluate the effect of exogenous OGP on in vitro fertilization (IVF) and embryo development in the pig using a defined serum-free culture system. In vitro-matured porcine oocytes were incubated with homologous OGP (0, 1, 10, 20, and 40 microg/ml) for 3 h and then washed prior to IVF. Exposure of oocytes to 10 or 20 microg/ml porcine OGP (pOGP) significantly reduced the incidence of polyspermy compared with the control (P < 0.01) while maintaining high penetration rates. When oocytes, spermatozoa, or both were preincubated with 10 microg/ml pOGP prior to IVF, the incidence of polyspermy was similarly reduced (P < 0.01) by all three treatments without affecting penetration rates. The ability of spermatozoa to undergo calcium ionophore-induced acrosome reaction was similar with or without exposure to pOGP. However, significantly fewer spermatozoa (P < 0.01) bound to the zona pellucida when oocytes were preincubated with pOGP. To evaluate the effect of pOGP on embryo development, embryos were cultured in pOGP-supplemented medium for 48 h or 144 h. Both transient and continuous exposure to pOGP significantly enhanced cleavage and blastocyst formation rate compared with the control (P < 0.01). These data demonstrate that exposure of either in vitro-matured oocytes or spermatozoa to pOGP decreased polyspermy and spermatozoa binding while maintaining high penetration rates of pig oocytes fertilized in vitro. Furthermore, pOGP exerted an embryotrophic effect independent of effects demonstrated on spermatozoa and oocytes at fertilization.

Effect of a null mutation of the oviduct-specific glycoprotein gene on mouse fertilization

The mammalian fertilization process takes place in a complex microenvironment within the female genital tract. A member of the chitinase protein family, oviduct-specific glycoprotein (OGP), has been identified in oviductal fluid from various mammalian species, including humans. Although OGP is widely believed to be involved in the process of mammalian fertilization, including spermatozoon function and gamete interactions, based on experimental results obtained in vitro, its physiological significance remains controversial. The present study established OGP gene-null ( ogp (-/-)) mice, and primarily characterized their reproductive properties to study the physiological function(s) of OGP. Results obtained from studies using an in vivo or in vitro system showed that the fertility of ogp (-/-) females was within normal limits. These results indicate that OGP is not essential for the process of in vivo fertilization, at least in mice.

Identification, cloning, and initial characterization of a novel mouse testicular germ cell-specific antigen

A monoclonal antibody, designated TES101, was raised by immunizing BALB/c mice with an allogenic mouse testicular homogenate followed by immunohistochemical selection as the initial screening method. By searching the expressed sequence tag (EST) database with the N-terminal amino acid sequence of TES101 reactive protein, we found that the predicted amino acid sequence encoded by a mouse testicular EST clone matched the TES101 protein sequence. Sequence analysis of the clone revealed no homologous molecule in the DNA/protein database. Based on data obtained from N-terminal amino acid analysis of the TES101 protein, the derived amino acid sequence contained a signal peptide region of 25 amino acids and a mature protein region of 225 amino acids, which translated into a protein with a molecular weight of 24 093. Northern blot analysis showed that mRNA of the TES101 protein was found in testis but not in any other mouse tissues examined. Western blot analysis revealed that TES101 reacted with a 38-kDa band on SDS-PAGE under nonreducing conditions, and this reactivity was abrogated under reducing conditions. Immunoelectron microscopic studies demonstrated that the molecule was predominantly located on the plasma membrane of spermatocytes and spermatids but not in Sertoli cells or interstitial cells, including Leydig cells. Thus, the TES101 protein is a novel molecule present primarily on the surface of developing male germ cells. TES101 protein may play a role in the processes underlying male germ cell formation.

Organization of a gene coding for an oviduct-specific glycoprotein (oviductin) in the hamster

Hamster oviductin, a high molecular weight glycoprotein secreted by the oviducts, is believed to participate in fertilization and protection of the tubal epithelium. Expression of the oviductin gene is confined strictly to nonciliated secretory cells of the oviduct and is regulated by hormones. The objective of this study was to characterize the genomic organization and to identify potential regulatory elements implicated in the control of transcription of the oviductin gene. Polymerase chain reaction was performed on hamster genomic DNA, yielding 2.2 kb of the 5' flanking region as well as 13.6 kb of genomic sequence comprising the entire coding sequence of the oviductin gene distributed in 11 exons. Sequencing of the 5' flanking region revealed, among other elements, an almost perfect estrogen-responsive element (GGTCACTGTGACT), an atypical TATA box (TATTAA), and a perfect inverted Sp1 site located between the transcription start site and the atypical TATA box. Primer extension analyses indicated that the hamster oviductin transcript possesses an unusually short 5' untranslated region of only 14 nucleotides. The distinct organization of the hamster oviductin gene in the vicinity of the transcription start site provides an interesting ground for further functional studies.

Effects of the porcine oviduct-specific glycoprotein on fertilization, polyspermy, and embryonic development in vitro

This study evaluated the effects of porcine oviduct-specific glycoprotein (pOSP) on in vitro fertilization (IVF), polyspermy, and development to blastocyst. Experiment 1 evaluated the effects of various concentrations (0-100 microgram/ml) of purified pOSP on fertilization parameters, including penetration, polyspermy, male pronuclear formation, and mean number of sperm penetrated per oocyte. Experiment 2 examined the ability of an anti-pOSP immunoglobulin G to inhibit the observed effects of pOSP on fertilization parameters. Experiments 3 and 4 examined various concentrations of pOSP (0-100 microgram/ml) on zona pellucida solubility and sperm binding, respectively. Lastly, experiment 5 assessed the effects of various concentrations of pOSP (0-100 microgram/ml) on the in vitro embryo cleavage rate and development to blastocyst. Pig oocytes matured and fertilized in vitro were used for all experiments. An effect of treatment (P < 0.05) was detected for pOSP on penetration, polyspermy, and mean number of sperm per oocyte. Concentrations for pOSP of 0-50 microgram/ml had no effect on sperm penetration rates; however, compared with the control, 100 microgram/ml significantly decreased the penetration rate (74% vs. 41%). Addition of 10-100 microgram/ml significantly reduced the polyspermy rate compared with the control (61% vs. 24-29%). The decrease in polyspermy achieved by addition of pOSP during preincubation and IVF was blocked with a specific antibody to pOSP. No effect of treatment was observed on zona digestion time relative to the control; however, the number of sperm bound to the zona pellucida was significantly decreased by treatment (P < 0.05). Compared with the control, all concentrations of pOSP examined reduced the number of sperm bound per oocyte (45 vs. 19-34). A treatment effect (P < 0.05) was observed for pOSP on embryo development to blastocyst but not on cleavage rates. Addition of pOSP during preincubation and fertilization significantly increased postcleavage development to blastocyst, but a synergistic stimulation on development was not detected when pOSP was included during in vitro culture. These results indicate that exposure to pOSP before and during fertilization reduces the incidence of polyspermy in pig oocytes, reduces the number of bound sperm, and increases postcleavage development to blastocyst.

Mouse oviduct-specific glycoprotein gene: genomic organization and structure of the 5'-flanking regulatory region

A member of the chitinase protein family, oviduct-specific glycoprotein (OGP), can directly associate with gametes or with the early embryo in the oviduct. Although the glycoprotein is widely distributed among mammalian species and there is indirect evidence concerning the involvement of the molecule in the fertilization process, its physiological functions are far from completely understood. To understand the fundamental mechanisms that direct gene expression as well as to know the physiological significance of OGP, we have isolated and characterized a mouse OGP gene (mogp-1). The gene was found to span 13.4 kilobases (kb) including 11 exons and 10 introns. The genomic organization of mogp-1 is well conserved compared to the other members of the chitinase family. Two transcription initiation sites were found at positions 18 and 14 upstream from the first ATG codon. Fluorescence in situ hybridization analysis demonstrated that the mogp-1 was located on the R-positive F3 band of mouse chromosome 3. Although the putative promoter region of mogp-1 lacked typical TATA, CAAT, or GC box sequences, the region contained several motif sequences of transcription factor binding sites including 10 half-palindromic estrogen responsive elements (ERE) and an imperfect ERE. Transient transfection experiments demonstrated that promoter activity could be modulated by various sequences within the 2.2 kb of the 5'-flanking region, and that the mogp-1 promoter was transactivated in an estrogen receptor-positive cell line, MCF-7, by the addition of estradiol-17beta (E(2)). In addition, relevant promoter activity for E(2) responsiveness resides within the first 270 base pairs upstream of the mogp-1. These findings should facilitate our understanding of the regulation of OGP gene expression, and they may be helpful for designing experiments to unravel the role of OGP in the process of mammalian fertilization.

A Novel Glycosylphosphatidyl Inositol-Anchored Protein on Human Leukocytes: A Possible Role for Regulation of Neutrophil Adherence and Migration

We report here a novel glycosylphosphatidyl-inositol (GPI)-anchored glycoprotein on human leukocytes. Treatment of neutrophils with a mAb (3H9) to this molecule sequentially up-regulates and down-regulates β2 integrin-dependent adhesion of these cells as well as their transendothelial migration in vitro. In addition, this mAb simultaneously modulates the avidity of β2 integrin for its ligand, iC3b, with kinetics similar to those observed in 3H9 modulation of neutrophil adherence. This mAb also induces β2 integrin-dependent cytoskeletal remodeling. This novel GPI-anchored protein (GPI-80) is highly homologous with Vanin-1, a recently reported GPI-anchored protein that is expressed on perivascular thymic stromal cells and is involved in thymus homing in mice. The finding that both GPI-80 and Vanin-1 are 40% homologous with human biotinidase suggests the existence of a biotinidase superfamily of molecules that may be involved in the regulation of leukocyte trafficking.

Mammalian chitinase-like proteins

Mammals express genes coding for proteins that show significant similarity to chitinases of family 18 glycosyl hydrolases. These chitinase-like proteins have no chitinase activity due to changes in critical residues in the putative active center. One of these is oviductin, a high molecular weight glycoprotein most likely involved in fertilization and protection of the tubal epithelium owing to its mucin character. Another is YKL-40 (HCgp39) produced in association with tissue remodeling. Such proteins could have a general function in morphogenesis.

Rat zona pellucida glycoproteins: molecular cloning and characterization of the three major components

The zona pellucida (ZP), the extracellular glycocalyx that surrounds the oocyte, is well known to mediate homologous gamete interaction. In a previous study from our laboratories, we reported the qualitative characterization of the rat ZP. The ZP in this species, like the mouse, hamster, and human, was found to contain three glycoproteins, namely rZP1, rZP2, and rZP3 (Araki et al. [1992] Biol Reprod 46:912-919). In this study, cDNAs encoding whole rat ZP major components have been isolated and characterized. A rat ovary cDNA library was screened with the mouse ZP3 and ZP2 cDNA probes, respectively. For rZP1 cDNA cloning, cDNAs generated using reverse transcriptase-polymerase chain reaction and rapid amplification of 5' and 3' cDNA ends, were isolated and sequenced. The rZP3 cDNA showed 1338 bp with a coding region containing 1272 bp, that translates into 424 amino acids. The total translation of rZP3 peptide has a molecular weight of 45,820, containing six potential N-glycosylation sites and 75 Ser/Thr residues, possible O-glycosylation sites. The amino acid sequence derived from the cDNA sequence shares high sequence homologies to mouse (90%), hamster (78%), and human (65%) ZP3 (ZPC) glycoproteins, indicating that the rat and mouse ZP3 have quite a conserved amino acid sequence, including the potential glycosylation sites. The total transcript of the rZP2 was 2154 nucleotides and the largest open reading frame was 695 amino acids. This would translate into a protein of 78.4 kDa. In the case of rZP1, the cDNA clone consisted of 1960 bp, and the coding region contained 1851 bp translating into 617 amino acids. Significant homologies were observed between rZP2 and ZPA family from various mammalian species. The rZP1 also showed a sequence homology to mouse ZP1, known as a mouse orthologue of ZPB family, suggesting that the rZP2 and rZP1 are members of ZPA and ZPB families, respectively. The message distributions for each zona components were limited within the ovary and the signal was detectable in the growing oocytes. The present results will further our understanding of the structure of rat zona components and lead to a better understanding of species-specificity observed during sperm-egg interaction.

Characterization of antibodies generated against a conserved portion of oviductal glycoprotein (OGP) and endogenous hamster OGP and their ability to decrease sperm binding to the zona pellucida in vitro

PROBLEM

The effect of antibodies generated against hamster oviductal glycoprotein (OGP) on sperm binding to the zona pellucida (ZP) was evaluated.

METHOD OF STUDY

Antibodies against a 17-amino-acid sequence of the OGP core protein (amino acids 52-68) and the denatured hamster OGP protein were generated, characterized, and tested in an in vitro sperm binding assay.

RESULTS

Sperm binding was significantly decreased (P < 0.05) when oviductal oocytes were incubated for 2 hr with 4 or 8 mg/ml of immune IgG of both antibodies when compared with normal rabbit IgG. A fluorescence assay showed binding of both antibodies to the endogenous OGP associated with the ZP of ovulated hamster oocytes.

CONCLUSIONS

These results suggest that OGP may be a potential immunocontraceptive target because both antibodies significantly decreased sperm binding to the ZP of oviductal oocytes. Immunocontraception may be accomplished by attempting to generate active immunity to a recombinant OGP, to the region selected in this study (amino acids 52-68) or to some other region of the core protein.

Purification and characterization of a silica-induced bronchoalveolar lavage protein with fibroblast growth-promoting activity

Experimentally induced silicosis provides a good model for chronic interstitial pulmonary inflammation and fibrosis. In the present study, a specific single polypeptide with an apparent molecular mass of 58,000 and a pl of 4.5 was purified and characterized from the bronchoalveolar lavage fluid of silicotic rats. The same protein was also isolated from both the extract and conditioned medium of alveolar macrophages of silicotic rats. Therefore, this protein was termed an inducible silicotic (rat) bronchoalveolar lavage protein-p58 (iSBLP58) or an inducible silicotic (rat) pulmonary macrophage factor (iSPMF-p58). iSBLP58 has been purified to homogeneity by a combination of gel permeation, Mono Q ion exchange, and reverse-phase high performance liquid chromatography. This polypeptide displayed a potent fibroblast growth-promoting activity in vitro. The sequence of the first 15 NH2-terminal amino acids was determined and was found to have high sequence homology with members of the mammalian chitinase-like protein family, which includes human cartilage gp39, mammalian oviduct-specific glycoprotein, and a secretory protein from activated mouse macrophages.

Allelic polymorphism and chromosomal localization of the human oviductin gene (MUC9)

OBJECTIVE

To determine if the gene coding for human oviductin (the estrogen-dependent, oviduct-specific glycoprotein with an affinity for the zona pellucida) shows length polymorphism in the region of tandem repeats. To determine the frequencies of the length alleles in health and disease.

DESIGN

Descriptive fundamental and clinical studies.

SETTING

Fertility clinic and research center, university teaching hospital.

PATIENT(S)

Fertile women, women with a history of ectopic pregnancy or tubal disease, and women with stage I or II endometriosis.

INTERVENTION(S)

Blood samples were drawn for DNA analysis.

MAIN OUTCOME MEASURE(S)

Length and sequence of the region of tandem repeats.

RESULT(S)

Four different length alleles of the human oviductin gene were identified. Their relative frequencies in pathologic cases were not statistically significant compared with those found in normal fertile women. The human genome contains a single copy of the oviductin gene located on chromosome 1p13.

CONCLUSION(S)

The human oviductin gene codes for a glycoprotein that shares the characteristics of epithelial mucins. Because eight epithelial mucin genes have been identified so far, we therefore propose to name this gene MUC9. The biologic function of the protein is likely to include protection of the early embryo and of the fallopian tube itself.

Species-specific effect of oviductal glycoproteins on hamster sperm binding to hamster oocytes

The secretory cells of the oviductal epithelium secrete a high-molecular-weight glycoprotein (OGP). OGPs from different mammalian species show similar immunological characteristics, their cDNAs show high homologies, and they associate with the zona pellucida of oviductal oocytes in vivo. The purpose of this study was to determine the effect of OGP obtained from different species on the binding of hamster sperm to hamster oocytes. Hamster oocytes were inseminated (30 min) in the presence or absence of homologous or heterologous OGPs, and sperm bound/oocyte were counted after removing loosely attached sperm. Ovarian oocytes had an average of 2.9 +/- 0.6 sperm bound/oocyte, whereas oviductal oocytes had 36.3 +/- 2.7. Hamster OGP (0.1 mg/ml) significantly increased sperm binding to ovarian oocytes twofold and had no effect on sperm bound/oviductal oocytes. Human OGP (0.5 mg/ml) significantly decreased sperm binding to ovarian oocytes (0.9 +/- 0.3 sperm bound/oocyte). This effect was dose dependent for oviductal oocytes and could be blocked by preincubating human OGP with a specific antibody to human OGP. The presence of baboon and cow OGP during the insemination of hamster oviductal oocytes also resulted in a significant decrease in sperm bound/oocyte, whereas the addition of hamster OGP to hamster oviductal oocytes had no effect. These results show that homologous OGP enhances sperm binding to the ZP, whereas heterologous OGP inhibits that effect. Thus, our results suggest that OGP plays a role in the species-specific characteristics of sperm/ZP interaction, and that one must use a homologous system (OGP and gametes from the same species) to study the biological effect of OGP.