Participation of cysteine-rich secretory proteins (CRISP) in mammalian sperm-egg interaction

Detection of Protein Biomarkers Relevant to Sperm Characteristics and Fertility in Semen in Three Wild Felidae: The Flat-Headed Cat (Prionailurus planiceps), Fishing Cat (Prionailurus viverrinus), and Asiatic Golden Cat (Catopuma temminckii)

Effective wild cat conservation programs with assisted reproductive technologies are being developed in different parts of the world. The flat-headed cat, fishing cat, and Asiatic golden cat are three species among nine wild Felidae in Thailand that are in need of urgent conservation efforts. Here, we assessed routine sperm characteristics and we report the detection of protein biomarkers related to the fertilization process, IZUMO1 and the CRISP family, and apoptotic markers, active or cleaved caspase-3, in semen samples collected from these wild cats. IZUMO1 was located in the equatorial segment of the sperm head, which is the region involved in gamete interaction. The highest levels of IZUMO1 were found in both the sperm pellet and the seminal plasma of the flat-headed cat, as determined by immunoblotting. CRISP2, a sperm-egg fusion assisting protein, and CRISP3 were found in both the sperm pellet and the seminal plasma, and the highest levels were observed in the fishing cat. Positive correlations between certain semen parameters and IZUMO1, CRISP2, and CRISP3 expression were also demonstrated. Cleaved caspase-3 was found in all sperm samples in all three species and was associated with an increase in DNA fragmentation and a decrease in certain semen characteristics such as motility, viability, and intact acrosomes. Our results suggest that the analysis of IZUMO1, the CRISP family, and cleaved caspase-3, along with the routine sperm characteristics, may allow for better success in breeding management in wild Felidae, particularly in the flat-headed cat and the fishing cat.

CRISPs Function to Boost Sperm Power Output and Motility

Fertilization requires sperm to travel long distances through the complex environment of the female reproductive tract. Despite the strong association between poor motility and infertility, the kinetics of sperm tail movement and the role individual proteins play in this process is poorly understood. Here, we use a high spatiotemporal sperm imaging system and an analysis protocol to define the role of CRISPs in the mechanobiology of sperm function. Each of CRISP1, CRISP2, and CRISP4 is required to optimize sperm flagellum waveform. Each plays an autonomous role in defining beat frequency, flexibility, and power dissipation. We thus posit that the expansion of the CRISP family from one member in basal vertebrates, to three in most mammals, and four in numerous rodents, represents an example of neofunctionalization wherein proteins with a common core function, boosting power output, have evolved to optimize different aspects of sperm tail performance.

Arrdc4-dependent extracellular vesicle biogenesis is required for sperm maturation

Extracellular vesicles (EVs) are important players in cell to cell communication in reproductive systems. Notably, EVs have been found and characterized in the male reproductive tract, however, direct functional evidence for their importance in mediating sperm function is lacking. We have previously demonstrated that Arrdc4, a member of the α-arrestin protein family, is involved in extracellular vesicle biogenesis and release. Here we show that Arrdc4-mediated extracellular vesicle biogenesis is required for proper sperm function. Sperm from Arrdc4-/- mice develop normally through the testis but fail to acquire adequate motility and fertilization capabilities through the epididymis, as observed by reduced motility, premature acrosome reaction, reduction in zona pellucida binding and two-cell embryo production. We found a significant reduction in extracellular vesicle production by Arrdc4-/- epididymal epithelial cells, and further, supplementation of Arrdc4-/- sperm with additional vesicles dampened the acrosome reaction defect and restored zona pellucida binding. These results indicate that Arrdc4 is important for proper sperm maturation through the control of extracellular vesicle biogenesis.

Characterization and biological role of cysteine-rich venom protein belonging to CRISPs from turkey seminal plasma†

Turkey semen contains cysteine-rich secretory proteins (CRISPs) that belong to the dominant seminal plasma proteins. We aimed to isolate and characterize CRISP from turkey seminal plasma and evaluate its possible involvement in yellow semen syndrome (YSS). YSS, which is well characterized, causes reduced fertility and hatchability. The protein was purified using hydrophobic interaction, gel filtration, and reverse phase chromatography. It then was subjected to identification by mass spectrometry, analysis of physicochemical properties, and specific antibody production. The biological function of the isolated protein was tested and included its effects on sperm motility and migration and sperm-egg interactions. Sperm motility was measured with the CASA system using Hobson Sperm Tracker. The reproductive tract of turkey toms was analyzed for gene expression; immunohistochemistry was used for protein localization in the male reproductive tract, spermatozoa, and inner perivitelline layer. The isolated protein was identified as cysteine-rich venom protein-like isoform X2 (CRVP X2; XP_010706464.1) and contained feature motifs of CRISP family proteins. Turkey CRVP X2 was present in both spermatozoa and seminal plasma. The extensive secretion of CRVP X2 by the epithelial cells of the epididymis and ductus deferens suggests its involvement in post-testicular sperm maturation. The internally localized CRVP X2 in the proximal part of the sperm tail might be responsible for stimulation of sperm motility. CRVP X2 on the sperm head might be involved in several events prior to fusion and may also participate in gamete fusion itself. Although the mechanisms by which CRVP X2 mediates fertilization are still unknown, the involvement of complementary sites cannot be excluded. The disturbance of CRVP X2 expression can serve as an etiologic factor of YSS in the turkey. This study expands the understanding of the detailed mechanism of fertilization in birds by clarifying the specific role of CRVP X2.

Novel Proteomic Profiling of Epididymal Extracellular Vesicles in the Domestic Cat Reveals Proteins Related to Sequential Sperm Maturation with Differences Observed between Normospermic and Teratospermic Individuals

Extracellular vesicles (EVs) secreted by the epididymal epithelium transfer to spermatozoa key proteins that are essential in promoting motility and subsequent fertilization success. Using the domestic cat model, the objectives were to (1) characterize and compare protein content of EVs between segments of the epididymis, and (2) compare EV protein compositions between normo- and teratospermic individuals (producing >60% of abnormal spermatozoa). Epididymal EVs from adult cats were isolated and assessed via liquid chromatography tandem MS. Both male types shared 3008 proteins in total, with 98 and 20 EV proteins unique to normospermic and teratospermic males, respectively. Expression levels of several proteins changed between epididymal segments in both male types. Several proteins in both groups were related to sperm motility (e.g. hexokinase 1, adenylate kinase isoenzyme) and zona pellucida or oolemma binding (e.g. disintegrin and metalloproteinase domain proteins, zona binding proteins 1 and 2). Interestingly, seven cauda-derived EV proteins trended downward in teratospermic compared with normospermic males, which may relate to poor sperm quality. Collective results revealed, for the first time, EV proteins related to sequential sperm maturation with differences observed between normospermic and teratospermic individuals.

Functional redundancy and compensation: Deletion of multiple murine Crisp genes reveals their essential role for male fertility

Mammalian Cysteine-RIch Secretory Protein (CRISP) family includes four members present in sperm and reported to regulate Ca²⁺ channels and fertilization. Based on our previous observations using single knockouts models and suggesting the existence of functional compensation among CRISP proteins, we investigated their relevance for male fertility by generating multiple Crisp gene mutants by CRISPR/Cas9 technology. Whereas targeting of Crisp1 and Crisp3 yielded subfertile males with early embryo developmental defects, the same deletion in zygotes from fertile Crisp2^-/- .Crisp4^-/- mice led to the generation of both triple and quadruple knockout mice exhibiting a complete or severe disruption of male fertility due to a combination of sperm transport, fertilization, and embryo developmental defects linked to intracellular Ca²⁺ dysregulation. These observations reveal that CRISP proteins are essential for male fertility and organize in functional modules that contribute distinctly to fertility success, bringing insights into the mechanisms underlying functional redundancy/compensation in protein families and emphasizing the importance of generating multiple and not just single knockout which might be masking the true functional relevance of family genes.

Does the Pre-Ovulatory Pig Oviduct Rule Sperm Capacitation In Vivo Mediating Transcriptomics of Catsper Channels?

Spermatozoa need to conduct a series of biochemical changes termed capacitation in order to fertilize. In vivo, capacitation is sequentially achieved during sperm transport and interaction with the female genital tract, by mechanisms yet undisclosed in detail. However, when boar spermatozoa are stored in the tubal reservoir pre-ovulation, most appear to be in a non-capacitated state. This study aimed at deciphering the transcriptomics of capacitation-related genes in the pig pre-ovulatory oviduct, following the entry of semen or of sperm-free seminal plasma (SP). Ex-vivo samples of the utero-tubal junction (UTJ) and isthmus were examined with a microarray chip (GeneChip^® Porcine Gene 1.0 ST Array, Thermo Fisher Scientific) followed by bioinformatics for enriched analysis of functional categories (GO terms) and restrictive statistics. The results confirmed that entry of semen or of relative amounts of sperm-free SP modifies gene expression of these segments, pre-ovulation. It further shows that enriched genes are differentially associated with pathways relating to sperm motility, acrosome reaction, single fertilization, and the regulation of signal transduction GO terms. In particular, the pre-ovulation oviduct stimulates the Catsper channels for sperm Ca²⁺ influx, with AKAPs, CATSPERs, and CABYR genes being positive regulators while PKIs and CRISP1 genes appear to be inhibitors of the process. We postulate that the stimulation of PKIs and CRISP1 genes in the pre-ovulation sperm reservoir/adjacent isthmus, mediated by SP, act to prevent premature massive capacitation prior to ovulation.

GLIPR1L1 is an IZUMO-binding protein required for optimal fertilization in the mouse

Background

The sperm protein IZUMO1 (Izumo sperm-egg fusion 1) and its recently identified binding partner on the oolemma, IZUMO1R, are among the first ligand-receptor pairs shown to be essential for gamete recognition and adhesion. However, the IZUMO1-IZUMO1R interaction does not appear to be directly responsible for promoting the fusion of the gamete membranes, suggesting that this critical phase of the fertilization cascade requires the concerted action of alternative fusogenic machinery. It has therefore been proposed that IZUMO1 may play a secondary role in the organization and/or stabilization of higher-order heteromeric complexes in spermatozoa that are required for membrane fusion.

Results

Here, we show that fertilization-competent (acrosome reacted) mouse spermatozoa harbor several high molecular weight protein complexes, a subset of which are readily able to adhere to solubilized oolemmal proteins. At least two of these complexes contain IZUMO1 in partnership with GLI pathogenesis-related 1 like 1 (GLIPR1L1). This interaction is associated with lipid rafts and is dynamically remodeled upon the induction of acrosomal exocytosis in preparation for sperm adhesion to the oolemma. Accordingly, the selective ablation of GLIPR1L1 leads to compromised sperm function characterized by a reduced ability to undergo the acrosome reaction and a failure of IZUMO1 redistribution.

Conclusions

Collectively, this study characterizes multimeric protein complexes on the sperm surface and identifies GLIPRL1L1 as a physiologically relevant regulator of IZUMO1 function and the fertilization process.

The Free Radical Diseases of Prematurity: From Cellular Mechanisms to Bedside

During the perinatal period, free radicals (FRs) are involved in several physiological roles such as the cellular responses to noxia, the defense against infectious agents, the regulation of cellular signaling function, and the induction of a mitogenic response. However, the overproduction of FRs and the insufficiency of an antioxidant mechanism result in oxidative stress (OS) which represents a deleterious process and an important mediator of damage to the placenta and the developing fetus. After birth, OS can be magnified by other predisposing conditions such as hypoxia, hyperoxia, ischemia, hypoxia ischemia-reperfusion, inflammation, and high levels of nonprotein-bound iron. Newborns are particularly susceptible to OS and oxidative damage due to the increased generation of FRs and the lack of adequate antioxidant protection. This impairment of the oxidative balance has been thought to be the common factor of the so-called “free radical related diseases of prematurity,” including retinopathy of prematurity, bronchopulmonary dysplasia, intraventricular hemorrhage, periventricular leukomalacia, necrotizing enterocolitis, kidney damage, and oxidative hemolysis. In this review, we provide an update focused on the factors influencing these diseases refining the knowledge about the role of OS in their pathogenesis and the current evidences of such relationship. Mechanisms governing FR formation and subsequent OS may represent targets for counteracting tissue damage.

Quantitative evolutionary proteomics of seminal fluid from primates with different mating systems

BACKGROUND

Genomic data from various organisms have been used to study how sexual selection has shaped genetic diversity in reproductive proteins, and in particular, to elucidate how mating systems may have influenced evolution at the molecular and phenotypic levels. However, large-scale proteomic data including protein identifications and abundances are only now entering the field of evolutionary and comparative genomics. Variation in both protein sequence and expression level may play important roles in the evolution of sexual traits and behaviors.

RESULTS

Here, we broadly analyze the components of seminal fluid from primates with diverse mating systems ranging from monogamous to polygynous, and include genomics, proteomics, phylogenetic and quantitative characters into our framework. Our analyses show that seminal fluid proteins are undergoing rapid evolution and some of these quickly evolving proteins may be influenced by sexual selection. Through evolutionary analyses and protein abundance differences, we identified 84 genes whose evolutionary rates or expression levels were correlated with mating system and other sexual characters. We found that many proteins differ in abundance between monogamous and polygynous primate mating systems. Many of these proteins are enriched in the copulatory plug pathway, which suggests that post-zygotic selective barriers are important regardless of mating system type.

CONCLUSIONS

This work is the first to comprehensively compare seminal fluid proteins between human and non-human primates using high-throughput proteomics. Our findings highlight the impact of mating system variation on seminal fluid protein evolution and abundance.

Gamete compatibility genes in mammals: candidates, applications and a potential path forward

Fertilization represents a critical stage in biology, where successful alleles of a previous generation are shuffled into new arrangements and subjected to the forces of selection in the next generation. Although much research has been conducted on how variation in morphological and behavioural traits lead to variation in fertilization patterns, surprisingly little is known about fertilization at a molecular level, and specifically about how genes expressed on the sperm and egg themselves influence fertilization patterns. In mammals, several genes have been identified whose products are expressed on either the sperm or the egg, and which influence the fertilization process, but the specific mechanisms are not yet known. Additionally, in 2014 an interacting pair of proteins was identified: 'Izumo' on the sperm, and 'Juno' on the egg. With the identification of these genes comes the first opportunity to understand the molecular aspects of fertilization in mammals, and to identify how the genetic characteristics of these genes influence fertilization patterns. Here, we review recent progress in our understanding of fertilization and gamete compatibility in mammals, which should provide a helpful guide to researchers interested in untangling the molecular mechanisms of fertilization and the resulting impacts on population biology and evolutionary processes.

Differential proteomic profiling in human spermatozoa that did or did not result in pregnancy via IVF and AID

PURPOSE

To identify biochemical markers in men with idiopathic infertility and normal sperm counts.

EXPERIMENTAL DESIGN

We obtained proteomic profiling proteins in human spermatozoa following successful or unsuccessful pregnancy via assisted reproductive technology (ART) using 6-plex tandem mass tag (TMT) isobaric mass spectrometry. Our study design consisted of two groups: 1. The semen of 6 men whose sperm resulted in a clinical pregnancy following ART and 6 men whose semen did not result in a clinical pregnancy following ART. The results of differentiated mass spectrometry were validated by Western blotting.

RESULTS AND DISCUSSION

A total of 2,045 proteins were detected in our cohort. 21 proteins were found to be differentially expressed (>1.2-fold) in men whose sperm resulted in a clinical pregnancy and those that did not. Using the results of bioinformatics analysis and Western Blotting, three proteins (A2LD1, ATP1B3 and FBXO2) were shown to have the same differential pattern (p<0.05) that was observed in the mass spectrometry analysis.

CONCLUSIONS AND CLINICAL RELEVANCE

Proteomics may help identity a select cohort of men with abnormal semen parameters and aide infertility diagnoses.

Cysteine-rich secretory protein 3 inhibits hepatitis C virus at the initial phase of infection

Hepatitis C virus (HCV) affects 2-3% of the global population. Approximately one-quarter of acute infections cause chronic hepatitis that leads to liver cirrhosis or hepatocellular carcinoma. The major obstacle of current research is the extremely narrow host tropism of HCV. A single HCV strain can replicate in the Huh7 human hepatoma cell line. Huh7 cells can be adapted under selective pressure in vitro to identify host factors that influence viral replication. Here, we extended this strategy to the in vivo condition and generated a series of cell lines by multiple rounds of adaptation in immunocompromised mice. Adaptation increased the cellular resistance to HCV infection. Microarray analyses revealed that the expression levels of several genes were associated with HCV resistance. Notably, up-regulation of the mRNA encoding cysteine-rich secretory protein 3 (CRISP3), a glycoprotein with unknown function that is secreted from multiple exocrine glands, was correlated with HCV resistance. The presence of CRISP3 in the culture medium limited HCV replication at the early phase of infection.

Detecting coevolution in mammalian sperm-egg fusion proteins

Interactions between sperm and egg proteins can occur physically between gamete surface-binding proteins, and genetically between gamete proteins that work in complementary pathways in which they may not physically interact. Physically interacting sperm-egg proteins have been functionally identified in only a few species, and none have been verified within mammals. Candidate genes on both the sperm and egg surfaces exist, but gene deletion studies do not support functional interactions between these sperm-egg proteins; interacting sperm-egg proteins thus remain elusive. Cooperative gamete proteins undergo rapid evolution, and it is predicted that these sperm-egg proteins will also have correlated evolutionary rates due to compensatory changes on both the sperm and egg. To explore potential physical and genetic interactions in sperm-egg proteins, we sequenced four candidate genes from diverse primate species, and used regression and likelihood methods to test for signatures of coevolution between sperm-egg gene pairs. With both methods, we found that the egg protein CD9 coevolves with the sperm protein IZUMO1, suggesting a physical or genetic interaction occurs between them. With regression analysis, we found that CD9 and CRISP2 have correlated rates of evolution, and with likelihood analysis, that CD9 and CRISP1 have correlated rates. This suggests that the different tests may reflect different levels of interaction, be it physical or genetic. Coevolution tests thus provide an exploratory method for detecting potentially interacting sperm-egg protein pairs.

TCTEX1D4 interactome in human testis: unraveling the function of dynein light chain in spermatozoa

Studies were designed to identify the TCTEX1D4 interactome in human testis, with the purpose of unraveling putative protein complexes essential to male reproduction and thus novel TCTEX1D4 functions. TCTEX1D4 is a dynein light chain that belongs to the DYNT1/TCTEX1 family. In spermatozoa, it appears to be important to sperm motility, intraflagellar transport, and acrosome reaction. To contribute to the knowledge on TCTEX1D4 function in testis and spermatozoa, a yeast two-hybrid assay was performed in testis, which allowed the identification of 40 novel TCTEX1D4 interactors. Curiously, another dynein light chain, TCTEX1D2, was identified and its existence demonstrated for the first time in human spermatozoa. Immunofluorescence studies proved that TCTEX1D2 is an intra-acrosomal protein also present in the midpiece, suggesting a role in cargo movement in human spermatozoa. Further, an in silico profile of TCTEX1D4 revealed that most TCTEX1D4 interacting proteins were not previously characterized and the ones described present a very broad nature. This reinforces TCTEX1D4 as a dynein light chain that is capable of interacting with a variety of functionally different proteins. These observations collectively contribute to a deeper molecular understanding of the human spermatozoa function.

Mammalian sperm fertility related proteins

Infertility is an important aspect of human and animal reproduction and still presents with much etiological ambiguity. As fifty percent of infertility is related to the male partner, molecular investigations on sperm and seminal plasma can lead to new knowledge on male infertility. Several comparisons between fertile and infertile human and other species sperm proteome have shown the existence of potential fertility markers. These proteins have been categorized into energy related, structural and other functional proteins which play a major role in sperm motility, capacitation and sperm-oocyte binding. The data from these studies show the impact of sperm proteome studies on identifying different valuable markers for fertility screening. In this article, we review recent development in unraveling sperm fertility related proteins.

Mapping of the binding sites involved in PSP94-CRISP-3 interaction by molecular dissection of the complex. Biochim Biophys Acta Gen Subj. 2013;1830:3019-3029. [PMID: 23375721 DOI: 10.1016/j.bbagen.2013.01.015]

BACKGROUND

Human Prostate Secretory Protein of 94 amino acids (PSP94) has been shown to bind human CRISP-3 (cysteine-rich secretory protein 3) with very high affinity. CRISP-3 belongs to the CRISP family of proteins having a PR-1 (pathogenesis related protein 1) domain at its N-terminal and ion channel regulatory (ICR) domain at its C-terminal connected by a hinge region. Functional significance of this complex is not yet known.

METHODS

In order to identify the residues and/or regions involved in PSP94-CRISP-3 interaction, site-directed mutagenesis was employed. Effect of the mutations on the interaction was studied by co-immunoprecipitation (Co-IP).

RESULTS

For PSP94, amino acids Y(3), F(4), P(56) and the C-terminal β-strand were found to be crucial for interacting with CRISP-3. A disulfide bond between the two domains of PSP94 (C(37)A-C(73)A) was also important for this interaction. In case of CRISP-3, the N-terminal domain alone could not maintain a strong interaction with PSP94 but it required presence of the hinge region and not the C-terminal domain. Apart from CRISP-3, CRISP-2 was also found to interact with human PSP94. Based on our findings the most likely model of PSP94-CRISP-3 complex has been proposed.

CONCLUSION

The terminal β-strands of PSP94 contact the first α-helix and the hinge region of CRISP-3.

GENERAL SIGNIFICANCE

Involvement of the hinge region of CRISPs in interaction with PSP94 may affect the domain movement of CRISPs essential for the ion-channel regulatory activity resulting in inhibition of this activity.

Evolution of genes involved in gamete interaction: evidence for positive selection, duplications and losses in vertebrates

Genes encoding proteins involved in sperm-egg interaction and fertilization exhibit a particularly fast evolution and may participate in prezygotic species isolation [1], [2]. Some of them (ZP3, ADAM1, ADAM2, ACR and CD9) have individually been shown to evolve under positive selection [3], [4], suggesting a role of positive Darwinian selection on sperm-egg interaction. However, the genes involved in this biological function have not been systematically and exhaustively studied with an evolutionary perspective, in particular across vertebrates with internal and external fertilization. Here we show that 33 genes among the 69 that have been experimentally shown to be involved in fertilization in at least one taxon in vertebrates are under positive selection. Moreover, we identified 17 pseudogenes and 39 genes that have at least one duplicate in one species. For 15 genes, we found neither positive selection, nor gene copies or pseudogenes. Genes of teleosts, especially genes involved in sperm-oolemma fusion, appear to be more frequently under positive selection than genes of birds and eutherians. In contrast, pseudogenization, gene loss and gene gain are more frequent in eutherians. Thus, each of the 19 studied vertebrate species exhibits a unique signature characterized by gene gain and loss, as well as position of amino acids under positive selection. Reflecting these clade-specific signatures, teleosts and eutherian mammals are recovered as clades in a parsimony analysis. Interestingly the same analysis places Xenopus apart from teleosts, with which it shares the primitive external fertilization, and locates it along with amniotes (which share internal fertilization), suggesting that external or internal environmental conditions of germ cell interaction may not be the unique factors that drive the evolution of fertilization genes. Our work should improve our understanding of the fertilization process and on the establishment of reproductive barriers, for example by offering new leads for experiments on genes identified as positively selected.

cSrc is necessary for epididymal development and is incorporated into sperm during epididymal transit

Changes that occur to mammalian sperm upon epididymal transit and maturation render these cells capable of moving progressively and capacitating. Signaling events leading to mammalian sperm capacitation depend on the modulation of proteins by phosphorylation and dephosphorylation cascades. Recent experiments have demonstrated that the Src family of kinases plays an important role in the regulation of these events. However, sperm from cSrc null mice display normal tyrosine phosphorylation associated with capacitation. We report here that, despite normal phosphorylation, sperm from cSrc null mice display a severe reduction in forward motility, and are unable to fertilize in vitro. Histological analysis of seminiferous tubules in the testes, caput and corpus epididymis do not reveal obvious defects. However, the cauda epididymis is significantly smaller, and expression of key transport proteins in the epithelial cells lining this region is reduced in cSrc null mice compared to wild type littermates. Although previously, we and others have shown the presence of cSrc in mature sperm from cauda epididymis, a closer evaluation indicates that this tyrosine kinase is not present in sperm from the caput epididymis, suggesting that this protein is acquired by sperm later during epididymal maturation. Consistent with this observation, cSrc is enriched in vesicles released by the epididymal epithelium known as epididymosomes. Altogether, these observations indicate that cSrc is essential for cauda epididymal development and suggest an essential role of this kinase in epididymal sperm maturation involving cSrc extracellular trafficking.

Egg jelly proteins stimulate directed motility in Xenopus laevis sperm

Previously we have shown that extracts from Xenopus egg jelly (egg water) increase the passage of sperm through a porous membrane in a dose-dependent manner. Although this assay has shown that sperm accumulation occurs only in the presence of an egg water gradient, it has not revealed the dynamic features of how Xenopus sperm swim in such gradients. Here, we use video microscopic observations to trace sperm trajectories in a Zigmond chamber. Our results show that Xenopus sperm swim in linear and gently curving paths and only infrequently perform turns. In the presence of an egg water gradient, however, the percent of sperm swimming up the gradient axis and the net distance traveled by each sperm along this axis was increased significantly. There was no change in curvilinear velocity. Rather, the orientation of sperm travel was shifted to more closely match that of the gradient axis. In addition, using a porous filter assay, we demonstrate that the egg water protein allurin, in both purified and recombinant forms, stimulates directed motility of sperm. Finally, we use Oregon Green 488-conjugated allurin to show that this protein binds primarily to the sperm midpiece; binding of allurin to the entire head was observed in a minor subpopulation of sperm. Dose dependence of allurin binding occurred over the 0-1 µg/ml range and correlated well with previously published dose-dependent sperm attraction data. Binding was rapid with a half-time of about 10 sec. These data suggest that egg water proteins bind to sperm and modify sperm-orienting behavior.

Loss of cysteine-rich secretory protein 4 (Crisp4) leads to deficiency in sperm-zona pellucida interaction in mice

Mammalian sperm gain their ability to fertilize the egg during transit through the epididymis and by interacting with proteins secreted by the epididymal epithelial cells. Certain members of the CRISP (cysteine-rich secretory protein) family form the major protein constituent of the luminal fluid in the mammalian epididymis. CRISP4 is the newest member of the CRISP family expressed predominantly in the epididymis. Its structure and expression pattern suggest a role in sperm maturation and/or sperm-egg interaction. To study the relevance of CRISP4 in reproduction, we have generated a Crisp4 iCre knock-in mouse model through insertion of the iCre recombinase coding cDNA into the Crisp4 locus. This allows using the mouse line both as a Crisp4 deficient model and as an epididymis-specific iCre-expressing mouse line applicable for the generation of conditional, epididymis-specific knockout mice. We show that the loss of CRISP4 leads to a deficiency of the spermatozoa to undergo progesterone-induced acrosome reaction and to a decreased fertilizing ability of the sperm in the in vitro fertilization conditions, although the mice remain fully fertile in normal mating. However, removal of the egg zona pellucida returned the fertilization potential of the CRISP4-deficient spermatozoa, and accordingly we detected a reduced number of Crisp4-deficient spermatozoa bound to oocytes as compared with the wild-type spermatozoa. We also demonstrate that iCre recombinase is expressed in a pattern similar to endogenous Crisp4 and is able to initiate the recombination event with its target sequences in vivo.

Allurin, an amphibian sperm chemoattractant having implications for mammalian sperm physiology

Eggs of many species are surrounded by extracellular coats that emit ligands to which conspecific sperm respond by undergoing chemotaxis and changes in metabolism, motility, and acrosomal status in preparation for fertilization. Here we review methods used to measure sperm chemotaxis and focus on recent studies of allurin, a 21-kDa protein belonging to the Cysteine-RIch Secretory Protein (CRISP) family that has chemoattraction activity for both amphibian and mammalian sperm. Allurin is unique in being the first extensively characterized Crisp protein found in the female reproductive tract and is the product of a newly discovered amphibian gene within a gene cluster that has been largely conserved in mammals. Study of its expression, function, and tertiary structure could lead to new insights in the role of Crisp proteins in sperm physiology.

Copy number changes of CRISP3 in oral squamous cell carcinoma

The aim of this study was to identify tumor suppressor genes (TSGs) in oral squamous cell carcinoma (OSCC) using whole-genome analysis of microarray technology and real-time quantitative polymerase chain reaction (QPCR). We applied whole-genome analysis of TSGs in the specimens from 3 patients of OSCC by microarray technology. A total of 11 genes, CRISP3, SCGB3A1, AGR2, PIP, C20orf114, TFF1, STATH, AZGP1, MUC7, DMBT1 and LOC389429, were found to be down-regulated, and 2, matrix metallopeptidase (MMP) 1 and MMP3, were found to be up-regulated in the 3 OSCC patients using microarray technology. In this study, we selected the CRISP3 gene. CRISP3 belongs to the cystein-rich secretary protein gene family in chromosome 6p12.3. CRISP3 has been found in the salivary gland, spleen and prostate gland and is a prominent biomarker in the gene expression of prostate cancer. Down-regulation of this gene was previously observed in OSCC. No studies examining the DNA copy number of CRISP3 in detail exist. We analyzed the DNA copy number of CRISP3 in 5 OSCC-derived cell lines (SAS, Ca9-22, KON, HSC2 and HSC4) and 60 OSCC tissues by real-time QPCR. The DNA copy number loss of CRISP3 was observed in 2 of the 5 OSCC-derived cell lines (SAS, HSC2) and in 24 of 60 patients (40.0%) using real-time QPCR. A significant statistical correlation between the copy number loss and gender and T classification was observed. These results indicate that the inactivation of CRISP3 is an early event in OSCC, since the T1/T2 classification is correlated with DNA copy number loss of CRISP3, whereas T3/T4 classification is not. We conclude that CRISP3 may be involved in the carcinogenesis of OSCC.

Mouse sperm exhibit chemotaxis to allurin, a truncated member of the cysteine-rich secretory protein family

Allurin, a 21 kDa protein isolated from egg jelly of the frog Xenopus laevis, has previously been demonstrated to attract frog sperm in two-chamber and microscopic assays. cDNA cloning and sequencing has shown that allurin is a truncated member of the Cysteine-Rich Secretory Protein (CRISP) family, whose members include mammalian sperm-binding proteins that have been postulated to play roles in spermatogenesis, sperm capacitation and sperm-egg binding in mammals. Here, we show that allurin is a chemoattractant for mouse sperm, as determined by a 2.5-fold stimulation of sperm passage across a porous membrane and by analysis of sperm trajectories within an allurin gradient as observed by time-lapse microscopy. Chemotaxis was accompanied by an overall change in trajectory from circular to linear thereby increasing sperm movement along the gradient axis. Allurin did not increase sperm velocity although it did produce a modest increase in flagellar beat frequency. Oregon Green 488-conjugated allurin was observed to bind to the sub-equatorial region of the mouse sperm head and to the midpiece of the flagellum. These findings demonstrate that sperm have retained the ability to bind and respond to truncated Crisp proteins over 300 million years of vertebrate evolution.

Calcium Channels in the Development, Maturation, and Function of Spermatozoa

A proper dialogue between spermatozoa and the egg is essential for conception of a new individual in sexually reproducing animals. Ca2+ is crucial in orchestrating this unique event leading to a new life. No wonder that nature has devised different Ca2+-permeable channels and located them at distinct sites in spermatozoa so that they can help fertilize the egg. New tools to study sperm ionic currents, and image intracellular Ca2+ with better spatial and temporal resolution even in swimming spermatozoa, are revealing how sperm ion channels participate in fertilization. This review critically examines the involvement of Ca2+ channels in multiple signaling processes needed for spermatozoa to mature, travel towards the egg, and fertilize it. Remarkably, these tiny specialized cells can express exclusive channels like CatSper for Ca2+ and SLO3 for K+, which are attractive targets for contraception and for the discovery of novel signaling complexes. Learning more about fertilization is a matter of capital importance; societies face growing pressure to counteract rising male infertility rates, provide safe male gamete-based contraceptives, and preserve biodiversity through improved captive breeding and assisted conception initiatives.

Structural studies of human glioma pathogenesis-related protein 1

Human glioma pathogenesis-related protein 1 (GLIPR1) is a membrane protein that is highly upregulated in brain cancers but is barely detectable in normal brain tissue. GLIPR1 is composed of a signal peptide that directs its secretion, a conserved cysteine-rich CAP (cysteine-rich secretory proteins, antigen 5 and pathogenesis-related 1 proteins) domain and a transmembrane domain. GLIPR1 is currently being investigated as a candidate for prostate cancer gene therapy and for glioblastoma targeted therapy. Crystal structures of a truncated soluble domain of the human GLIPR1 protein (sGLIPR1) solved by molecular replacement using a truncated polyalanine search model of the CAP domain of stecrisp, a snake-venom cysteine-rich secretory protein (CRISP), are presented. The correct molecular-replacement solution could only be obtained by removing all loops from the search model. The native structure was refined to 1.85 Å resolution and that of a Zn2+ complex was refined to 2.2 Å resolution. The latter structure revealed that the putative binding cavity coordinates Zn2+ similarly to snake-venom CRISPs, which are involved in Zn2+-dependent mechanisms of inflammatory modulation. Both sGLIPR1 structures have extensive flexible loop/turn regions and unique charge distributions that were not observed in any of the previously reported CAP protein structures. A model is also proposed for the structure of full-length membrane-bound GLIPR1.

Identification and localization of the sperm CRISP family protein CiUrabin involved in gamete interaction in the ascidian Ciona intestinalis

Ascidians are hermaphrodites, and most release sperm and eggs nearly simultaneously. Many species, including Halocynthia roretzi and Ciona intestinalis, are self-sterile. We previously reported that the interaction between a 12 EGF-like repeat-containing vitelline-coat (VC) protein, HrVC70, and a sperm GPI-anchored CRISP, HrUrabin, in lipid rafts plays a key role in self-/nonself-recognizable gamete interaction in H. roretzi. On the other hand, we recently identified two pairs of polymorphic genes responsible for self-incompatibility in C. intestinalis by positional cloning: The sperm polycystin 1-like receptors s-Themis-A/B and its fibrinogen-like ligand v-Themis-A/B on the VC. However, it is not known if the orthologs of HrVC70 and HrUrabin also participate in gamete interaction in C. intestinalis since they are from different orders. Here, we tested for a C. intestinalis ortholog (CiUrabin) of HrUrabin by searching the genome database and proteomes of sperm lipid rafts. The identified CiUrabin belongs to the CRISP family, with a PR domain and a GPI-anchor-attachment site. CiUrabin appears to be specifically expressed in the testis and localized at the surface of the sperm head, as revealed by Northern blotting and immunocytochemistry, respectively. The specific interaction between CiVC57, a C. intestinalis ortholog of HrVC70, and CiUrabin was confirmed by Far Western analysis, similarly to the interaction between HrVC70 and HrUrabin. The molecular interaction between CiVC57 and CiUrabin may be involved in the primary binding of sperm to the VC prior to the allorecognition process, mediated by v-Themis-A/B and s-Themis-A/B, during fertilization of C. intestinalis.

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.

Oxygen toxicity: chemistry and biology of reactive oxygen species

Oxygen has a central role in the evolution of complex life on Earth mainly because of the biochemical symmetry of oxygenic photosynthesis and aerobic respiration that can maintain homeostasis within our planet biosphere. Oxygen can also produce toxic molecules, reactive oxygen species (ROS). ROS is a collective term that includes both oxygen radicals and certain oxidizing agents that are easily converted into radicals. They can be produced from both endogenous and exogenous substances. ROS play a dual role in biological systems, since they can be either harmful or beneficial to living systems. They can be considered a double-edged sword because on the one hand oxygen-dependent reactions and aerobic respiration have significant advantages but, on the other, overproduction of ROS has the potential to cause damage.

Isolation of transcripts from Diabrotica virgifera virgifera LeConte responsive to the Bacillus thuringiensis toxin Cry3Bb1

Crystal (Cry) proteins derived from Bacillus thuringiensis (Bt) have been widely used as a method of insect pest management for several decades. In recent years, a transgenic corn expressing the Cry3Bb1 toxin has been successfully used for protection against corn rootworm larvae (genus Diabrotica). The biological action of the Bt toxin in corn rootworms has not yet been clearly defined. Because development of resistance to Bt by corn rootworms will have huge economic and ecological costs, insight into larval response to Bt toxin is highly desirable. We identified 19 unique transcripts that are differentially expressed in D. virgifera virgifera larvae reared on corn transgenic for Cry3Bb1. Putative identities of these genes were consistent with impacts on metabolism and development. Analysis of highly modulated transcripts resulted in the characterization of genes coding for a member of a cysteine-rich secretory protein family and a glutamine-rich membrane protein. A third gene that was isolated encodes a nondescript 132 amino acid protein while a fourth highly modulated transcript could not be further characterized. Expression patterns of these four genes were strikingly different between susceptible and resistant western corn rootworm populations. These genes may provide useful targets for monitoring of Bt exposure patterns and resistance development in pest and non-target insect populations.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 5: intercellular junctions and contacts between germs cells and Sertoli cells and their regulatory interactions, testicular cholesterol, and genes/proteins associated with more than one germ cell generation

In the testis, cell adhesion and junctional molecules permit specific interactions and intracellular communication between germ and Sertoli cells and apposed Sertoli cells. Among the many adhesion family of proteins, NCAM, nectin and nectin-like, catenins, and cadherens will be discussed, along with gap junctions between germ and Sertoli cells and the many members of the connexin family. The blood-testis barrier separates the haploid spermatids from blood borne elements. In the barrier, the intercellular junctions consist of many proteins such as occludin, tricellulin, and claudins. Changes in the expression of cell adhesion molecules are also an essential part of the mechanism that allows germ cells to move from the basal compartment of the seminiferous tubule to the adluminal compartment thus crossing the blood-testis barrier and well-defined proteins have been shown to assist in this process. Several structural components show interactions between germ cells to Sertoli cells such as the ectoplasmic specialization which are more closely related to Sertoli cells and tubulobulbar complexes that are processes of elongating spermatids embedded into Sertoli cells. Germ cells also modify several Sertoli functions and this also appears to be the case for residual bodies. Cholesterol plays a significant role during spermatogenesis and is essential for germ cell development. Lastly, we list genes/proteins that are expressed not only in any one specific generation of germ cells but across more than one generation.

Human CRISP-3 binds serum alpha(1)B-glycoprotein across species

BACKGROUND

CRISP-3 was previously shown to be bound to alpha(1)B-glycoprotein (A1BG) in human serum/plasma. All mammalian sera are supposed to contain A1BG, although its presence in rodent sera is not well-documented. Since animal sera are often used to supplement buffers in experiments, in particular such that involve cell cultures, binding proteins present in sera might interfere in the experiments.

METHODS

We examined sera from five different animal species for CRISP-3 binding proteins using gel filtration and ligand blotting. We developed a rapid method for isolation of proteins that bind to human CRISP-3 and identified the isolated proteins by mass spectrometry and N-terminal sequencing.

RESULTS

We identified A1BG as a CRISP-3 binding protein in sera from cow, horse and rabbit. CRISP-3 bound kininogen 1 in mouse serum, whereas rat serum showed no CRISP-3 binding activity. In equine serum, we furthermore detected a possible CRISP, already bound to A1BG.

GENERAL SIGNIFICANCE

It seems to be a common mechanism that A1BGs bind CRISPs, also across species. Apart from the possible physiological implications hereof, complex binding of CRISPs by A1BG (and other proteins) may interfere with the detection and function of CRISPs, when these are studied in the presence of animal sera.

Reactive oxygen and nitrogen species in normal physiological processes

Abstract Reactive oxygen species (ROS) and reactive nitrogen species have generally been considered as being highly reactive and cytotoxic molecules. Besides their noxious effects, ROS participate in physiological processes in a carefully regulated manner. By way of example, microbicidal ROS are produced in professional phagocytes, ROS function as short-lived messengers having a role in signal transduction and, among other processes, participate in the synthesis of the iodothyronine hormones, reproduction, apoptosis and necrosis. Because of their ability to mediate a crosstalk between key molecules, their role might be dual (at least in some cases). The levels of ROS increase from a certain age, being associated with various diseases typical of senescence. The aim of this review is to summarize the recent findings on the physiological role of ROS. Other issues addressed are an increase in ROS levels during ageing, and the possibility of the physiological nature of this process.

Battle and ballet: molecular interactions between the sexes in Drosophila

Varied and fascinating interactions occur between males and females to lead to the production of progeny. Interactions between the sexes continue even after the act of mating-but at the molecular and cellular level instead of between individual animals. Molecules transferred from males to females during mating (via the seminal fluid) exert potent effects on females' physiology and (at least in some animals) on behavior. Taking advantage of genetic, genomic, and biochemical tools for Drosophila, we investigate molecular interactions that underlie this form of chemical communication. Recent data show that molecules and cells from both sexes participate in this "ballet," facilitating the mutually beneficial outcome of increased progeny production. Examples to be presented include the storage and utilization of sperm in the mated female, and a proteolytic pathway that begins in the male but ends in the female and involves both male and female contributions. Despite the joint benefit of increased progeny production, the "interests" of the mating male can differ from those of his mate. Over evolutionary time this disconnect can, in theory, precipitate a "battle" between the sexes, potentially leading to the rapid sequence changes that have been observed for some seminal proteins across species.

Novel epididymal proteins as targets for the development of post-testicular male contraception

Apart from condoms and vasectomy, modern contraceptive methods for men are still not available. Besides hormonal approaches to stop testicular sperm production, the post-meiotic blockage of epididymal sperm maturation carries lots of promise. Microarray and proteomics techniques and libraries of expressed sequence tags, in combination with digital differential display tools and publicly available gene expression databases, are being currently used to identify and characterize novel epididymal proteins as putative targets for male contraception. The data reported indicate that these technologies provide complementary information for the identification of novel highly expressed genes in the epididymis. Deleting the gene of interest by targeted ablation technology in mice or using immunization against the cognate protein are the two preferred methods to functionally validate the function of novel genesin vivo. In this review, we summarize the current knowledge of several epididymal proteins shown eitherin vivoorin vitroto be involved in the epididymal sperm maturation. These proteins include CRISP1, SPAG11e, DEFB126, carbonyl reductase P34H, CD52, and GPR64. In addition, we introduce novel proteinases and protease inhibitor gene families with potentially important roles in regulating the sperm maturation process. Furthermore, potential contraceptive strategies as well as delivery methods will be discussed. Despite the progress made in recent years, further studies are needed to reveal further details in the epididymal sperm maturation process and the factors involved, in order to facilitate the development of new epididymal contraceptives.