Fetuin-B, a Liver-Derived Plasma Protein Is Essential for Fertilization

Characterisation of reproductive tract microbiome and immune biomarkers for bovine genital campylobacteriosis in vaccinated and unvaccinated heifers

Background

Bovine genital campylobacteriosis (BGC) is a globally important venereal disease of cattle caused by Campylobacter fetus subspecies venerealis. Diagnosis of BGC is highly challenging due to the lack of accurate diagnostic tests.

Methods

To characterise the biomarkers for C. fetus venerealis infection, a total of twelve cycling heifers were selected and categorised as vaccinated (n = 6) with Vibrovax® (Zoetis™) and unvaccinated (n = 6). All heifers were oestrous synchronised with a double dose of prostaglandin (PGF2α) 11 days apart and when in oestrous intravaginally challenged with 2.7 x 109 CFU live C. fetus venerealis. DNA extracted from vaginal mucus samples was screened using a C. fetus qPCR and 16S rRNA was characterised using Illumina sequencing (V5-V8 region). Relative abundances of serum proteins were calculated using sequential window acquisition of all theoretical fragment ion spectra coupled to tandem mass spectrometry (SWATH-MS) for all heifers at three timepoints: pre-challenge, post-challenge and post-recovery.

Results

In 16S rRNA sequencing of vaginal mucus, Campylobacter spp. appeared two days following challenge in unvaccinated compared to 14 days in vaccinated animals, consistent with the qPCR results. Increased relative abundances of Firmicutes and Campylobacterota were identified after C. fetus venerealis challenge and were associated with C. fetus venerealis in vaccinated and unvaccinated heifers. Greater relative abundance of Streptococcus spp. was observed during oestrous rather than dioestrous. In both vaccinated and unvaccinated heifers, Acinetobacter spp. increased after challenge with higher abundance of Corynebacterium spp. in the vaccinated group. A total of 130 unique proteins were identified in SWATH analysis of the serum samples, and the number of differentially abundant proteins found was higher in the vaccinated group after recovery from infection compared to pre-and post-challenge (adjusted P < 0.05 and Log2FC > 0.2).

Conclusion

Coglutinin, clusterin, HP homologs, vitamin D binding protein and fetuin B were identified as potential biomarkers for C. fetus venerealis infection and need further study to validate their efficiency as immune biomarkers for BGC.

Identification of energy metabolism anomalies and serum biomarkers in the progression of premature ovarian failure via extracellular vesicles' proteomic and metabolomic profiles

BACKGROUND

Premature ovarian failure (POF) is a clinical condition characterized by the cessation of ovarian function, leading to infertility. The underlying molecular mechanisms remain unclear, and no predictable biomarkers have been identified. This study aimed to investigate the protein and metabolite contents of serum extracellular vesicles to investigate underlying molecular mechanisms and explore potential biomarkers.

METHODS

This study was conducted on a cohort consisting of 14 POF patients and 16 healthy controls. The extracellular vesicles extracted from the serum of each group were subjected to label-free proteomic and unbiased metabolomic analysis. Differentially expressed proteins and metabolites were annotated. Pathway network clustering was conducted with further correlation analysis. The biomarkers were confirmed by ROC analysis and random forest machine learning.

RESULTS

The proteomic and metabolomic profiles of POF patients and healthy controls were compared. Two subgroups of POF patients, Pre-POF and Pro-POF, were identified based on the proteomic profile, while all patients displayed a distinguishable metabolomic profile. Proteomic analysis suggested that inflammation serves as an early factor contributing to the infertility of POF patients. For the metabolomic analysis, despite the dysfunction of metabolism, oxidative stress and hormone imbalance were other key factors appearing in POF patients. Signaling pathway clustering of proteomic and metabolomic profiles revealed the progression of dysfunctional energy metabolism during the development of POF. Moreover, correlation analysis identified that differentially expressed proteins and metabolites were highly associated, with six of them being selected as potential biomarkers. ROC curve analysis, together with random forest machine learning, suggested that AFM combined with 2-oxoarginine was the best diagnostic biomarker for POF.

CONCLUSIONS

Omics analysis revealed that inflammation, oxidative stress, and hormone imbalance are factors that damage ovarian tissue, but the progressive dysfunction of energy metabolism might be the critical pathogenic pathway contributing to the development of POF. AFM combined with 2-oxoarginine serves as a precise biomarker for clinical POF diagnosis.

Associations between exposure to phthalates and liver function among women undergoing assisted reproductive technology

Phthalates can induce hepatotoxicity in animal studies. We aimed to assess the associations of individual and mixture of urinary phthalate metabolites with serum liver function indicators among 764 women undergoing assisted reproductive technology (ART). In linear models, we observed inverse correlations between urinary mono-benzyl phthalate and serum total protein (TP) as well as globulin (β=-0.27 and -0.23, respectively, P<0.05). Additionally, negative associations were identified between mono-isobutyl phthalate and mono-butyl phthalate (MBP) and aspartate aminotransferase-to-alanine transaminase ratio (AST/ALT) (P<0.05). MBP and the sum of all phthalate metabolites (∑all.phth.m) were positively associated with bilirubin, with β ranging from 0.14 to 0.47. Most phthalate metabolites were also positively related to gamma-glutamyl transferase (GGT) (all P<0.05). In Bayesian kernel machine regression models, phthalate mixture was positively associated with bilirubin and GGT, whereas inversely associated with AST/ALT and TP. Our results suggest that phthalate exposure may impair liver function among women undergoing ART.

Substrate profiling of the metalloproteinase ovastacin uncovers specific enzyme-substrate interactions and discloses fertilization-relevant substrates

The metalloproteinase ovastacin is released by the mammalian egg upon fertilization and cleaves a distinct peptide bond in zona pellucida protein 2 (ZP2), a component of the enveloping extracellular matrix. This limited proteolysis causes zona pellucida hardening, abolishes sperm binding, and thereby regulates fertility. Accordingly, this process is tightly controlled by the plasma protein fetuin-B, an endogenous competitive inhibitor. At present, little is known about how the cleavage characteristics of ovastacin differ from closely related proteases. Physiological implications of ovastacin beyond ZP2 cleavage are still obscure. In this study, we employed N-terminal amine isotopic labeling of substrates (N-TAILS) contained in the secretome of mouse embryonic fibroblasts to elucidate the substrate specificity and the precise cleavage site specificity. Furthermore, we were able to unravel the physicochemical properties governing ovastacin-substrate interactions as well as the individual characteristics that distinguish ovastacin from similar proteases, such as meprins and tolloid. Eventually, we identified several substrates whose cleavage could affect mammalian fertilization. Consequently, these substrates indicate newly identified functions of ovastacin in mammalian fertilization beyond zona pellucida hardening.

Comparative Serum Proteome Profiling of Canine Benign Prostatic Hyperplasia before and after Castration

BPH is the most prevalent prostatic condition in aging dogs. Nevertheless, clinical diagnosis and management remain inconsistent. This study employed in-solution digestion coupled with nano-liquid chromatography tandem mass spectrometry to assess serum proteome profiling of dogs with BPH and those dogs after castration. Male dogs were divided into two groups; control and BPH groups. In the BPH group, each dog was evaluated at two time points: Day 0 (BF subgroup) and Day 30 after castration (AT subgroup). In the BF subgroup, three proteins were significantly upregulated and associated with dihydrotestosterone: solute carrier family 5 member 5, tyrosine-protein kinase, and FRAT regulator of WNT signaling pathway 1. Additionally, the overexpression of polymeric immunoglobulin receptors in the BF subgroup hints at its potential as a novel protein linked to the BPH development process. Conversely, alpha-1-B glycoprotein (A1BG) displayed significant downregulation in the BF subgroup, suggesting A1BG's potential as a predictive protein for canine BPH. Finasteride was associated with increased proteins in the AT subgroup, including apolipoprotein C-I, apolipoprotein E, apolipoprotein A-II, TAO kinase 1, DnaJ homolog subfamily C member 16, PH domain and leucine-rich repeat protein phosphatase 1, neuregulin 1, and pseudopodium enriched atypical kinase 1. In conclusion, this pilot study highlighted alterations in various serum proteins in canine BPH, reflecting different pathological changes occurring in this condition. These proteins could be a source of potential non-invasive biomarkers for diagnosing this disease.

Adropin may regulate corpus luteum formation and its function in adult mouse ovary

BACKGROUND

Adropin, a unique peptide hormone, has been associated with the regulation of several physiological processes, including glucose homeostasis, fatty acid metabolism, and neovascularization. However, its possible role in ovarian function is not understood. Our objective was to examine the expression of adropin and its putative receptor, GPR19, in the ovaries of mice at various phases of the estrous cycle.

METHODS

Immunohistochemistry and western blot analysis were performed to explore the localization and changes in expression of adropin and GPR19 in the ovaries during different phases of the estrous cycle in mice. Hormonal assays were performed with ELISA. An in vitro study was performed to examine the direct effect of adropin (10, 100 ng/ml) on ovarian function.

RESULTS

A western blot study showed that adropin and GPR19 proteins were maximum during the estrus phase of the estrous cycle. Interestingly, adropin and GPR19 displayed intense immunoreactivity in granulosa cells of large antral follicles and corpus luteum. This suggested the possible involvement of adropin in corpus luteum formation. Adropin treatment stimulated progesterone synthesis by increasing GPR19, StAR, CYP11A1, and 3β-HSD expressions, while it decreased estrogen synthesis by inhibiting 17β-HSD and aromatase protein expressions. Moreover, adropin treatment upregulated the cell cycle arrest-CDK inhibitor 1B (p27kip1), pERK1/2, and angiogenic protein (EG VEGF) that are involved in the process of luteinization.

CONCLUSIONS

Adropin GPR19 signaling promotes the synthesis of progesterone and upregulates the expression of p27kip1, EG VEGF, and erk1/2, resulting in cell cycle arrest and neovascularization, which ultimately leads to corpus luteum formation.

CRISPR/Cas9 technology: applications in oocytes and early embryos

CRISPR/Cas9, a highly versatile genome-editing tool, has garnered significant attention in recent years. Despite the unique characteristics of oocytes and early embryos compared to other cell types, this technology has been increasing used in mammalian reproduction. In this comprehensive review, we elucidate the fundamental principles of CRISPR/Cas9-related methodologies and explore their wide-ranging applications in deciphering molecular intricacies during oocyte and early embryo development as well as in addressing associated diseases. However, it is imperative to acknowledge the limitations inherent to these technologies, including the potential for off-target effects, as well as the ethical concerns surrounding the manipulation of human embryos. Thus, a judicious and thoughtful approach is warranted. Regardless of these challenges, CRISPR/Cas9 technology undeniably represents a formidable tool for genome and epigenome manipulation within oocytes and early embryos. Continuous refinements in this field are poised to fortify its future prospects and applications.

Ovastacin: An oolemma protein that cleaves the zona pellucida to prevent polyspermy

Monospermy occurs in the process of normal fertilization where a single sperm fuses with the egg, resulting in the formation of a diploid zygote. During the process of fertilization, the sperm must penetrate the zona pellucida (ZP), the outer layer of the egg, to reach the egg's plasma membrane. Once a sperm binds to the ZP, it undergoes an acrosomal reaction, which involves the release of enzymes from the sperm's acrosome that help it to penetrate the ZP. Ovastacin is one of the enzymes that is involved in breaking down the ZP. Studies have shown that ovastacin is necessary for the breakdown of the ZP and for successful fertilization to occur. However, the activity of ovastacin is tightly regulated to ensure that only one sperm can fertilize the egg. One way in which ovastacin helps to prevent polyspermy (the fertilization of an egg by more than one sperm) is by rapidly degrading the ZP after a sperm has penetrated it. This makes it difficult for additional sperm to penetrate the ZP and fertilize the egg. Ovastacin is also thought to play a role in the block to polyspermy, a mechanism that prevents additional sperm from fusing with the egg's plasma membrane after fertilization has occurred. In summary, the role of ovastacin in monospermic fertilization is to help ensure that only one sperm can fertilize the egg, while preventing polyspermy and ensuring successful fertilization.

In silico identification and characterization of the SNPs in the human ASTL gene and their probable role in female infertility

Ovastacin (ASTL), a zinc metalloprotease, is released from a fertilized egg during exocytosis of cortical granules which occurs minutes after the sperm and egg fuse. ASTL cleaves ZP2, one of the four primary glycoproteins of human zona pellucida, and this cleavage prevents polyspermy, causes zona pellucida hardening, and also protects the pre-implantation embryo. Any perturbation in the activity of ASTL can thus disturb this process and may lead to infertility without changing the gross morphology of the oocyte. A small amount of ASTL is also released by unfertilized oocytes but its catalytic activity is absent as it is bound by its inhibitor, Fetuin-B (FETUB). Pre-mature release of ASTL when FETUB is absent also causes infertility. To identify and understand the structural and functional effects of deleterious SNPs of ASTL on its interaction with ZP2 and FETUB and hence on fertility, a total of 4,748 SNPs from the dbSNP database were evaluated using a variety of in silico tools. All of the 40 shortlisted nsSNPs were present in the catalytic domain of the protein. Comparison of the wild type with mutants using MutPred2 suggests an alteration in the catalytic activity/zinc binding site in many SNPs. Docking studies show the involvement of hydrophobic interactions and H bonding between ASTL and ZP2 and also between ASTL and FETUB. Four positions in ASTL involved in the hydrophobic interactions (P¹⁰⁵ and D²⁰⁰ between ASTL and ZP2; D¹⁹⁸ and L²⁷⁸ between ASTL and FETUB) and 5 in H bonding (E⁷⁵ and R¹⁵⁹ between ASTL and ZP2; and K⁹³, R^159, and C²⁸¹ between ASTL and FETUB) have SNP's associated with them validating their importance. Interestingly, a cluster of multiple SNPs was found in the motif ¹⁹⁸DRD²⁰⁰, which is also a well-conserved region among several species. Statistical Coupling Analysis (SCA) suggested that the deleterious SNPs were present in the functionally important amino acid positions of ASTL and are evolutionarily coupled. Thus, these results attempt to identify the regions in ASTL, mutations in which can affect its binding with ZP2 or FETUB and cause female infertility.

Viscoelastic Properties of Zona Pellucida of Oocytes Characterized by Transient Electrical Impedance Spectroscopy

The success rate in vitro fertilization is significantly linked to the quality of the oocytes. The oocyte's membrane is encapsulated by a shell of gelatinous extracellular matrix, called zona pellucida, which undergoes dynamic changes throughout the reproduction cycle. During the window of highest fertility, the zona pellucida exhibits a softening phase, while it remains rigid during oocyte maturation and again after fertilization. These variations in mechanical properties facilitate or inhibit sperm penetration. Since successful fertilization considerably depends on the state of the zona pellucida, monitoring of the hardening process of the zona pellucida is vital. In this study, we scrutinized two distinct genetic mouse models, namely, fetuin-B wild-type and fetuin-B/ovastacin double deficient with normal and super-soft zona pellucida, respectively. We evaluated the hardening with the help of a microfluidic aspiration-assisted electrical impedance spectroscopy system. An oocyte was trapped by a microhole connected to a microfluidic channel by applying suction pressure. Transient electrical impedance spectra were taken by microelectrodes surrounding the microhole. The time-depending recovery of zona pellucida deflections to equilibrium was used to calculate the Young's modulus and, for the first time, absolute viscosity values. The values were obtained by fitting the curves with an equivalent mechanical circuit consisting of a network of dashpots and springs. The observer-independent electrical readout in combination with a fitting algorithm for the calculation of the viscoelastic properties demonstrates a step toward a more user-friendly and easy-to-use tool for the characterizing and better understanding of the rheological properties of oocytes.

Biomechanical forces and signals operating in the ovary during folliculogenesis and their dysregulation: implications for fertility

BACKGROUND

Folliculogenesis occurs in the highly dynamic environment of the ovary. Follicle cyclic recruitment, neo-angiogenesis, spatial displacement, follicle atresia and ovulation stand out as major events resulting from the interplay between mechanical forces and molecular signals. Morphological and functional changes to the growing follicle and to the surrounding tissue are required to produce oocytes capable of supporting preimplantation development to the blastocyst stage.

OBJECTIVE AND RATIONALE

This review will summarize the ovarian morphological and functional context that contributes to follicle recruitment, growth and ovulation, as well as to the acquisition of oocyte developmental competence. We will describe the changes occurring during folliculogenesis to the ovarian extracellular matrix (ECM) and to the vasculature, their influence on the mechanical properties of the ovarian tissue, and, in turn, their influence on the regulation of signal transduction. Also, we will outline how their dysregulation might be associated with pathologies such as polycystic ovary syndrome (PCOS), endometriosis or premature ovarian insufficiency (POI). Finally, for each of these three pathologies, we will highlight therapeutic strategies attempting to correct the altered biomechanical context in order to restore fertility.

SEARCH METHODS

For each area discussed, a systematic bibliographical search was performed, without temporal limits, using PubMed Central, Web of Science and Scopus search engines employing the keywords extracellular matrix, mechanobiology, biomechanics, vasculature, angiogenesis or signalling pathway in combination with: ovary, oogenesis, oocyte, folliculogenesis, ovarian follicle, theca, granulosa, cumulus, follicular fluid, corpus luteum, meiosis, oocyte developmental competence, preimplantation, polycystic ovary syndrome, premature ovarian insufficiency or endometriosis.

OUTCOMES

Through search engines queries, we yielded a total of 37 368 papers that were further selected based on our focus on mammals and, specifically, on rodents, bovine, equine, ovine, primates and human, and also were trimmed around each specific topic of the review. After the elimination of duplicates, this selection process resulted in 628 papers, of which 287 were cited in the manuscript. Among these, 89.2% were published in the past 22 years, while the remaining 8.0%, 2.4% or 0.3% were published during the 1990s, 1980s or before, respectively. During folliculogenesis, changes occur to the ovarian ECM composition and organization that, together with vasculature modelling around the growing follicle, are aimed to sustain its recruitment and growth, and the maturation of the enclosed oocyte. These events define the scenario in which mechanical forces are key to the regulation of cascades of molecular signals. Alterations to this context determine impaired folliculogenesis and decreased oocyte developmental potential, as observed in pathological conditions which are causes of infertility, such as PCOS, endometriosis or POI.

WIDER IMPLICATIONS

The knowledge of these mechanisms and the rules that govern them lay a sound basis to explain how follicles recruitment and growth are modulated, and stimulate insights to develop, in clinical practice, strategies to improve follicular recruitment and oocyte competence, particularly for pathologies like PCOS, endometriosis and POI.

Combined proteomics and transcriptomics identifies serpin family C member 1 associated protein as a biomarker of endometriosis

OBJECTIVE

To explore potential biomarkers indicating endometriosis (EM).

MATERIALS AND METHODS

A proteomics method and combined quantitative transcriptomics were adopted to highlight markers in the EM. Venn analysis was used to integrate the ribonucleic acid sequencing (RNA-seq) and protein profiles. Promising candidate markers were tested by enzyme-related immunosorbent assay.

RESULTS

A sum of 979 mRNAs and 39 proteins were tested to be significantly differentially expression in the standard cluster compared with the EM cluster. Venn analysis showed a filtered signature of only two down-regulated molecules in the EM group, i.e. fetuin B (FETUB) and serpin family C member 1 (SERPINC1); the latter showed a big variance between the control category and the EM set in the authentication test.

CONCLUSION

SERPINC1 may be a useful possible biomarker for the analysis of EM.

Reorganization, specialization, and degradation of oocyte maternal components for early development

Background

Oocyte components are maternally provided, solely determine oocyte quality, and coordinately determine embryo quality with zygotic gene expression. During oocyte maturation, maternal organelles are drastically reorganized and specialized to support oocyte characteristics. A large number of maternal components are actively degraded after fertilization and gradually replaced by zygotic gene products. The molecular basis and the significance of these processes on oocyte/embryo quality are not fully understood.

Methods

Firstly, recent findings in organelle characteristics of other cells or oocytes from model organisms are introduced for further understanding of oocyte organelle reorganization/specialization. Secondly, recent progress in studies on maternal components degradation and their molecular mechanisms are introduced. Finally, future applications of these advancements for predicting mammalian oocyte/embryo quality are discussed.

Main findings

The significance of cellular surface protein degradation via endocytosis for embryonic development, and involvement of biogenesis of lipid droplets in embryonic quality, were recently reported using mammalian model organisms.

Conclusion

Identifying key oocyte component characteristics and understanding their dynamics may lead to new applications in oocyte/embryo quality prediction and improvement. To implement these multidimensional concepts, development of new technical approaches that allow us to address the complexity and efficient studies using model organisms are required.

The structure, biosynthesis, and biological roles of fetuin-A: A review

Fetuin-A is a heterodimeric plasma glycoprotein containing an A-chain of 282 amino acids and a B-chain of 27 amino acid residues linked by a single inter-disulfide bond. It is predominantly expressed in embryonic cells and adult hepatocytes, and to a lesser extent in adipocytes and monocytes. Fetuin-A binds with a plethora of receptors and exhibits multifaceted physiological and pathological functions. It is involved in the regulation of calcium metabolism, osteogenesis, and the insulin signaling pathway. It also acts as an ectopic calcification inhibitor, protease inhibitor, inflammatory mediator, anti-inflammatory partner, atherogenic factor, and adipogenic factor, among other several moonlighting functions. Fetuin-A has also been demonstrated to play a crucial role in the pathogenesis of several disorders. This review mainly focuses on the structure, synthesis, and biological roles of fetuin-A. Information was gathered manually from various journals via electronic searches using PubMed, Google Scholar, HINARI, and Cochrane Library from inception to 2022. Studies written in English and cohort, case-control, cross-sectional, or experimental studies were considered in the review, otherwise excluded.

Role of Fetuin-A in the Pathogenesis of Psoriasis and Its Potential Clinical Applications

Fetuin-A is a plasma glycoprotein exhibiting multifaceted physiological and pathological functions. It has been determined to be involved in various essential biological functions, such as regulation of calcium metabolism, osteogenesis, and insulin signaling pathway. It also plays a crucial role in the pathogenesis of several disorders, including psoriasis. Psoriasis is a chronic systemic inflammatory disorder caused by a constellation of environmental, immunogenic, and genetic factors. It has been shown that dysregulation of cytokines mediated immune response is responsible for the development of psoriasis. Several recent publications suggest that dysregulation of fetuin-A correlates with psoriasis disease activities, revealing its putative role in the development of psoriasis. Furthermore, clinical application of fetuin-A as a diagnostic marker, prognostic predictor, and therapeutic target for different clinical conditions is in progress, and some are showing promising outcomes. This review primarily focuses on the current understanding of the role of fetuin-A in the pathogenesis of psoriasis and its potential clinical applications, with a brief highlight of psoriasis epidemiology and burden. The information was gathered systematically from various journals via electronic searches using various search engines: PubMed, Google Scholar, HINARI, and Cochrane Library from inception to 2022. The studies involved were restricted to English language. Conversely, articles written in other languages, studies done on fetuin B, or studies conducted on other dermatological diseases were excluded from the review article.

The Relationships among Plasma Fetuin-B, Thyroid Autoimmunity, and Fertilization Rate In Vitro Fertilization and Embryo Transfer

OBJECTIVE

The objective of the study is to investigate the relationships between fetuin-B, thyroid autoimmunity (TAI), and pregnancy outcomes in women undergoing in vitro fertilization and embryo transfer (IVF-ET). Design, Patients, and Measurements. In this prospective study, 180 women who were preparing for pregnancy with IVF-ET were included. There were 120 women with TAI positive and 60 negative controls matched with age and BMI.

RESULTS

The 180 women had mean ± SD age of 31.4 ± 4.0 years, with a mean ± SD BMI of 21.0 ± 1.6 kg/m². There was a significant difference in the level of fetuin-B in women with TAI positive compared with TAI negative group (65.2 ± 18.5 vs. 76.4 ± 25.1, P=0.001). Fetuin-B had a negative relationship with thyroid antibodies even after adjusting for other variables (OR (95%CI) = 0.98 (0.96-0.99), P=0.002). Compared with women with TAI negative, those with TAI positive had a significantly higher risk of low fertilization (20.0% vs. 6.7%; P=0.035). And we found no difference in terms of pregnancy, abortion, implantation, and live birth rate between the two groups. Logistic regression analysis showed that both fetuin-B and TAI were the independent factors to lead the low fertilization of IVF-ET (OR (95%CI) = 0.96 (0.94-0.99) and 4.084 (1.39-15.30), P=0.004 and 0.019, respectively).

CONCLUSION

Fetuin-B was significantly associated with TAI and low fertilization rate in women undergoing IVF-ET. Decreased fetuin-B in women with TAI may be the underlying reason for the lower IVF-ET success rate.

Proteolysis in Reproduction: Lessons From Gene-Modified Organism Studies

The physiological roles of proteolysis are not limited to degrading unnecessary proteins. Proteolysis plays pivotal roles in various biological processes through cleaving peptide bonds to activate and inactivate proteins including enzymes, transcription factors, and receptors. As a wide range of cellular processes is regulated by proteolysis, abnormalities or dysregulation of such proteolytic processes therefore often cause diseases. Recent genetic studies have clarified the inclusion of proteases and protease inhibitors in various reproductive processes such as development of gonads, generation and activation of gametes, and physical interaction between gametes in various species including yeast, animals, and plants. Such studies not only clarify proteolysis-related factors but the biological processes regulated by proteolysis for successful reproduction. Here the physiological roles of proteases and proteolysis in reproduction will be reviewed based on findings using gene-modified organisms.

ASTL is mutated in female infertility

Female infertility is a relatively common phenotype with a growing number of single gene causes although these account for only a minority of cases. Here, we report a consanguineous family in which adult females who are homozygous for a truncating variant in ASTL display markedly reduced fertility in a pattern strikingly similar to Astl^-/- female mice. ASTL encodes ovastacin, which is known to trigger zona pellucida hardening (ZPH) as part of the cortical reaction upon fertilization. ZPH is required for normal early embryonic development and its absence can be caused by pathogenic variants in other zona pellucida proteins that result in a similar infertility phenotype in humans and mouse. This is the first report of ASTL-related infertility in humans and suggests that the inclusion of ASTL in female infertility gene panels is warranted.

Knockin' on Egg's Door: Maternal Control of Egg Activation That Influences Cortical Granule Exocytosis in Animal Species

Fertilization by multiple sperm leads to lethal chromosomal number abnormalities, failed embryo development, and miscarriage. In some vertebrate and invertebrate eggs, the so-called cortical reaction contributes to their activation and prevents polyspermy during fertilization. This process involves biogenesis, redistribution, and subsequent accumulation of cortical granules (CGs) at the female gamete cortex during oogenesis. CGs are oocyte- and egg-specific secretory vesicles whose content is discharged during fertilization to block polyspermy. Here, we summarize the molecular mechanisms controlling critical aspects of CG biology prior to and after the gametes interaction. This allows to block polyspermy and provide protection to the developing embryo. We also examine how CGs form and are spatially redistributed during oogenesis. During egg activation, CG exocytosis (CGE) and content release are triggered by increases in intracellular calcium and relies on the function of maternally-loaded proteins. We also discuss how mutations in these factors impact CG dynamics, providing unprecedented models to investigate the genetic program executing fertilization. We further explore the phylogenetic distribution of maternal proteins and signaling pathways contributing to CGE and egg activation. We conclude that many important biological questions and genotype–phenotype relationships during fertilization remain unresolved, and therefore, novel molecular players of CG biology need to be discovered. Future functional and image-based studies are expected to elucidate the identity of genetic candidates and components of the molecular machinery involved in the egg activation. This, will open new therapeutic avenues for treating infertility in humans.

Combined approaches identify known and novel genes associated with sheep litter size and non-seasonal breeding

Improvement of ewe reproduction is considerable by appropriately increasing litter size and sustaining non-seasonal breeding. However, their genetic makeups have not been entirely elucidated. Genome-wide analyses of 821 individuals were performed by combining three genomic approaches (genome-wide association study, XP-nSL, and runs of homozygosity). Consequently, 35 candidate genes including three domestication genes (TSHR, GTF2A1, and KITLG) were identified. Other than the FecB mutation at BMPR1B, we described a significant association of a missense mutation rs406686139 at seasonal lambing-associated TSHR gene with litter size. Some promising novel genes may be relevant for sheep reproduction by multitude biological processes, such as FETUB functioning in fertilization, HNRNPA1 in oogenesis, DCUN1D1 in spermatogenesis, and HRG in fertility outcome. The present study suggests that improvement of ewe reproduction is attributed to selective breeding, and casts light on the genetic basis and improvement of sheep reproduction.

Molecular and pathobiological involvement of fetuin-A in the pathogenesis of NAFLD

The liver acts as a manufacturing unit for the production of fetuin-A, which is essential for various physiological characteristics. Scientific research has shown that a moderate upward push in fetuin-A serum levels is associated with a confirmed non-alcoholic fatty liver disease (NAFLD) diagnosis. Fetuin-A modulation is associated with a number of pathophysiological variables that cause liver problems, including insulin receptor signaling deficiencies, adipocyte dysfunction, hepatic inflammation, fibrosis, triacylglycerol production, macrophage invasion, and TLR4 activation. The focus of the present review is on the various molecular pathways, and genetic relevance of mRNA expression of fetuin-A which is correlated with progression of NAFLD. The other major area of exploration in the present review is based on the new targets for the modulation of fetuin-A, like calorie restriction and novel pharmacological agents, such as rosuvastatin, metformin, and pioglitazone which are successfully implicated in the management of various liver-related complications.

Comparative iTRAQ proteomics identified proteins associated with sperm maturation between yak and cattleyak epididymis

Background

During maturation, spermatozoa acquire motility and fertilizing capacity as they transit through the epididymis. In recent years, two-dimensional gel electrophoresis has been employed in proteomics studies conducted in rat, boar and human. However, there has not been a complete information regarding the proteins associated with sperm maturation in the epididymis. In this study, we employed iTRAQ proteomics to investigate proteins associated with sperm maturation between yak and cattleyak epididymis.

Results

After a successful sampling and protein extraction, the iTRAQ coupled with LC-MS/MS mass spectrometry and bioinformatics analysis were performed. We identified 288 differentially abundant proteins (DAPs) between yak and cattleyak epididymis; 151 were up-regulated while 137 were down-regulated in cattleyak relative to yak. Gene Ontology analysis identified that down-regulated DAPs in cattleyak were mostly enriched in the acetylation of protein component, along with negative and positive regulatory activities. iTRAQ proteomics data showed that the top up-regulated DAPs were mainly enriched in cell communication, cell adhesion, cytoskeleton organization, stress response, post-translational modifications and metabolic functions while the down-regulated DAPs were predominantly associated with sperm maturation, long-term sperm storage, sperm forward motility, sperm-oocyte fusion and regulatory functions.

Conclusion

These results provide insight into the molecular mechanisms underlying male cattleyak sterility.

The crystal structure of a 250-kDa heterotetrameric particle explains inhibition of sheddase meprin β by endogenous fetuin-B

Meprin β (Mβ) is a multidomain type-I membrane metallopeptidase that sheds membrane-anchored substrates, releasing their soluble forms. Fetuin-B (FB) is its only known endogenous protein inhibitor. Herein, we analyzed the interaction between the ectodomain of Mβ (MβΔC) and FB, which stabilizes the enzyme and inhibits it with subnanomolar affinity. The MβΔC:FB crystal structure reveals a ∼250-kDa, ∼160-Å polyglycosylated heterotetrameric particle with a remarkable glycan structure. Two FB moieties insert like wedges through a "CPDCP trunk" and two hairpins into the respective peptidase catalytic domains, blocking the catalytic zinc ions through an "aspartate switch" mechanism. Uniquely, the active site clefts are obstructed from subsites S₄ to S₁₀', but S₁ and S₁' are spared, which prevents cleavage. Modeling of full-length Mβ reveals an EGF-like domain between MβΔC and the transmembrane segment that likely serves as a hinge to transit between membrane-distal and membrane-proximal conformations for inhibition and catalysis, respectively.

Limited proteolysis by acrosin affects sperm-binding and mechanical resilience of the mouse zona pellucida

The encounter of oocyte and sperm is the key event initiating embryonic development in mammals. Crucial functions of this existential interaction are determined by proteolytic enzymes, such as acrosin, carried in the sperm head acrosome, and ovastacin, stored in the oocyte cortical granules. Ovastacin is released upon fertilisation to cleave the zona pellucida, a glycoprotein matrix surrounding the oocyte. This limited proteolysis hardens the oocyte envelope, and thereby provides a definitive block against polyspermy and protects the developing embryo. On the other hand, acrosin, the renowned and most abundant acrosomal protease, has been thought to enable sperm to penetrate the oocyte envelope. Depending on the species, proteolytic cleavage of the zona pellucida by acrosin is either essential or conducive for fertilisation. However, the specific target cleavage sites and the resulting physiological consequences of this proteolysis remained obscure. Here, we treated native mouse zonae pellucidae with active acrosin and identified two cleavage sites in zona pellucida protein 1 (ZP1), five in ZP2 and one in ZP3 by mass spectrometry. Several of these sites are highly conserved in mammals. Remarkably, limited proteolysis by acrosin leads to zona pellucida remodelling rather than degradation. Thus, acrosin affects both sperm binding and mechanical resilience of the zona pellucida, as assessed by microscopy and nanoindentation measurements, respectively. Furthermore, we ascertained potential regulatory effects of acrosin, via activation of latent pro-ovastacin and inactivation of fetuin-B, a tight binding inhibitor of ovastacin. These results offer novel insights into the complex proteolytic network modifying the extracellular matrix of the mouse oocyte, which might apply also to other species.

Heteroaromatic Inhibitors of the Astacin Proteinases Meprin α, Meprin β and Ovastacin Discovered by a Scaffold-Hopping Approach

Astacin metalloproteinases, in particular meprins α and β, as well as ovastacin, are emerging drug targets. Drug-discovery efforts have led to the development of the first potent and selective inhibitors in the last few years. However, the most recent compounds are based on a highly flexible tertiary amine scaffold that could cause metabolic liabilities or decreased potency due to the entropic penalty upon binding to the target. Thus, the aim of this study was to discover novel conformationally constrained scaffolds as starting points for further inhibitor optimization. Shifting from flexible tertiary amines to rigid heteroaromatic cores resulted in a boost in inhibitory activity. Moreover, some compounds already exhibited higher activity against individual astacin proteinases compared to recently reported inhibitors and also a favorable off-target selectivity profile, thus qualifying them as very suitable chemical probes for target validation.

Role of Zinc (Zn) in Human Reproduction: A Journey from Initial Spermatogenesis to Childbirth

Zinc (Zn), the second-most necessary trace element, is abundant in the human body. The human body lacks the capacity to store Zn; hence, the dietary intake of Zn is essential for various functions and metabolism. The uptake of Zn during its transport through the body is important for proper development of the three major accessory sex glands: the testis, epididymis, and prostate. It plays key roles in the initial stages of germ cell development and spermatogenesis, sperm cell development and maturation, ejaculation, liquefaction, the binding of spermatozoa and prostasomes, capacitation, and fertilization. The prostate releases more Zn into the seminal plasma during ejaculation, and it plays a significant role in sperm release and motility. During the maternal, labor, perinatal, and neonatal periods, the part of Zn is vital. The average dietary intake of Zn is in the range of 8-12 mg/day in developing countries during the maternal period. Globally, the dietary intake of Zn varies for pregnant and lactating mothers, but the average Zn intake is in the range of 9.6-11.2 mg/day. The absence of Zn and the consequences of this have been discussed using critical evidence. The events and functions of Zn related to successful fertilization have been summarized in detail. Briefly, our current review emphasizes the role of Zn at each stage of human reproduction, from the spermatogenesis process to childbirth. The role of Zn and its supplementation in in vitro fertilization (IVF) opens opportunities for future studies on reproductive biology.

Combination of fetuin and trehalose in presence of low glycerol has beneficial effects on freeze-thawed ram spermatozoa

BACKGROUND

Freeze-thawing process negatively affects ram spermatozoa in terms of sperm quality, DNA integrity and antioxidant defence system. Thus, antioxidant supplementation of spermatozoa during freeze-thawing is suggested to improve sperm parameters.

OBJECTIVES

The aim of this study was to determine the effects of fetuin and trehalose added into ram semen extender on sperm parameters, antioxidant parameters, antioxidant-related gene expressions and DNA integrity during the freeze-thawing process, in low glycerol concentration.

METHODS

Semen samples collected from six mature rams were pooled and splitted into equal aliquots and diluted with a tris-based extender containing different concentrations of glycerol (G5; %5 and G3; %3), fetuin (F; 2.5, 5 and 15 mg/mL) and trehalose (60 mm) as eight groups (G5F0, G5F2.5, G5F5, G5F15, G3F0, G3F2.5, G3F5 and G3F15).

RESULTS

G3F5 group resulted in the highest motility, mitochondrial activity and viability and the lowest DNA fragmentation and DNA damage (p < 0.05). Also, G3F0 displayed considerably more cryoprotective effect compared with G5F0 group (p < 0.05) in terms of motility, mitochondrial activity and viability rates. Lipid peroxidation levels decreased in G5F5 group compared with G5F0 group (p < 0.05). The levels of total glutathione increased in G3F2.5 group (p < 0.05) in comparison with the G5F0 group. NQO1 gene levels were upregulated approximately twofold in G5F5, G5F15, G3F2.5, G3F5 and G3F15 groups compared with G5F0 group (p < 0.05). The levels of GCLC gene were approximately twofold higher in G3F0, G3F2.5, G3F5 and G3F15 groups compared with G5F0 group (p < 0.05). GSTP1 gene levels were significantly higher with different levels in all treatment groups except for G5F2.5 and G3F0 groups in comparison with G5F0 group (p < 0.05).

CONCLUSIONS

Co-supplementation of tris-based extender having low glycerol (3%) with trehalose and fetuin to enhance the quality of ram spermatozoa after freeze-thawing process is recommended.

Comparative transcriptome of reproductive axis in Chinese indigenous sheep with different FecB genotypes and prolificacies

In the present study, there were 128, 263, and 139 differentially expressed genes (DEGs) from the ovary, pituitary, and hypothalamus, respectively, with the FecB B+/FecB ++ genotype. Results indicated that there was a synchronized, and differential increase in mRNA transcript abundances for genes encoding for ovarian steroidogenesis-signaling proteins in the ovary, TGF-β-signaling in hypothalamus, cAMP-signaling-transduction, and dopaminergic-synapse pathways in the pituitary. The values for these variables were associated with mean prolificacy in indigenous sheep and results provided indications for candidate regulator proteins that coordinate processes related to prolificacy in ewes. Furthermore, the results when there was evaluation of the FecB-genotype-specific co-expression modules implied that CYP17 was the hub gene connecting the pathways and for modulation of folliculogenesis and ovulation in the ewe with the FecB B+ genotype.

Fetuin B overexpression suppresses proliferation, migration, and invasion in prostate cancer by inhibiting the PI3K/AKT signaling pathway

Fetuin B (FETUB) is a glycoprotein that is a member of the cysteine protease inhibitor family, and it is associated with cancer. However, the role of FETUB in prostate carcinogenesis is unknown. In this study, we overexpressed FETUB in prostate cancer cells by using lentivirus and then studied the impacts on cell apoptosis, migration and invasion. We found that apoptosis was increased and the migration and invasion of prostate cancer cells were significantly inhibited after overexpression. Then, we performed experiments in vivo and found that there were fewer tumors in the overexpression groups than in the control groups. In addition, we demonstrated that overexpression of FETUB inactivates the PI3K/AKT signaling pathway. Rescue assays revealed that intervention of 740Y-P reversed the anti-tumor effect of FETUB on prostate cancer cells. Taken together, our results revealed that FETUB may act as a novel regulator to promote apoptosis and inhibit the migration and invasion of prostate cancer cells and that FETUB is related to the inactivation of the PI3K/AKT signaling pathway.

Addition of exogenous proteins detected in oviductal secretions to in vitro culture medium does not improve the efficiency of in vitro fertilization in pigs

This work was designed to study whether HSP70-1A, HSP90α, ezrin or PDI4, proteins previously identified in porcine oviductal secretions, have a role in zona pellucida (ZP) resistance to enzymatic digestion, in vitro fertilization (IVF) and sperm viability. In vitro matured porcine cumulus oocyte complexes were denuded and i) incubated for 1 h in TALP medium supplemented or not with each exogenous oviductal protein and in presence or absence of heparin to assess ZP digestion time by pronase; and ii) inseminated with fresh ejaculated boar spermatozoa in medium supplemented or not with each exogenous oviductal protein to assess their effect on fertilization results. Finally, spermatozoa were incubated in Tyrode's medium (0, 1 and 20 h) supplemented or not with HSP-701A, HSP-90α or ezrin, to assess simultaneously sperm viability and acrosome status by means of flow cytometry. Although all proteins increased the ZP digestion time, this increase was lower than 1 min, being ezrin the protein with a stronger effect. Presence of heparin in the medium reinforced the ZP hardening effect of ezrin and HSP-701A up to one more min, but not HSP-90α nor PDI4. Sperm penetration, but not IVF efficiency, increased when gametes were cocultured in medium containing PDIA4 whereas sperm penetration and polyspermy rates decreased in presence of ezrin and HSP proteins. This reduction was not the result of a detrimental effect of proteins on sperm viability or acrosome reaction. In conclusion, addition of exogenous proteins detected in oviductal secretions to artificial media does not reproduce the effect of adding such secretions nor improve the final efficiency of the porcine IVF system.

A Primary Evaluation of Potential Small-Molecule Inhibitors of the Astacin Metalloproteinase Ovastacin, a Novel Drug Target in Female Infertility Treatment

Despite huge progress in hormonal therapy and improved in vitro fertilization methods, the success rates in infertility treatment are still limited. A recently discovered mechanism revealed the interplay between the plasma protein fetuin-B and the cortical granule-based proteinase ovastacin to be a novel key mechanism in the regulation of fertilization. Upon sperm-egg fusion, cleavage of a distinct zona pellucida component by ovastacin destroys the sperm receptor, enhances zona robustness, and eventually provides a definitive block against polyspermy. An untimely onset of this zona hardening prior to fertilization would consequently result in infertility. Physiologically, this process is controlled by fetuin-B, an endogenous ovastacin inhibitor. Here we aimed to discover small-molecule inhibitors of ovastacin that could mimic the effect of fetuin-B. These compounds could be useful lead structures for the development of specific ovastacin inhibitors that can be used in infertility treatment or in vitro fertilization.

An exome-wide exploration of cases of primary ovarian insufficiency uncovers novel sequence variants and candidate genes

Primary ovarian insufficiency (POI) implies the cessation of menstruation for several months in women before the age of 40 years and is a major cause of infertility. The study of the contribution of genetic factors to POI has been fueled by the use of whole exome sequencing (WES). Here, to uncover novel causative pathogenic variants and risk alleles, WES has been performed in 12 patients with familial POI (eight unrelated index cases and two pairs of sisters) and six women with early menopause and family history of POI (four index cases and one pair of sisters). Likely causative variants in NR5A1 and MCM9 genes were identified as well as a variant in INHA that requires further investigation. Moreover, we have identified more than one candidate variant in 3 out of 15 familial cases. Taken together, our results highlight the genetic heterogeneity of POI and early menopause and support the hypothesis of an oligogenic inheritance of such conditions, in addition to monogenic inheritance.

Protein Expression Profile in IVF Follicular Fluid and Pregnancy Outcome Analysis in Euthyroid Women with Thyroid Autoimmunity

The objective of this study is to investigate the influence of the thyroid autoantibodies on the protein expression in follicular fluid and the clinical outcome of assisted reproductive technology. A total of 602 patients treated for infertility were screened; 49 euthyroid women who were positive for thyroid autoantibodies and 63 negative controls were recruited. Follicular fluid samples were analyzed using proteomics. Validation of target proteins in follicular fluid was performed by using parallel reaction monitoring. Differentially expressed proteins in follicular fluid, clinical pregnancy rate, abortion rate, and live-birth rate were analyzed. Clinical pregnancy rates and take-home baby rates in the thyroid autoimmunity (TAI) group were less than in the control group, but abortion rates in the TAI group were higher than in the control group (all P < 0.005). A total of 49 proteins were differentially expressed in the TAI-positive group. In Gene Ontology secondary annotations of all the proteins identified, five types of proteins were associated with the reproductive process. Among 11 proteins quantitatively identified by parallel reaction monitoring, angiotensinogen and fetuin-B were associated with reproduction. These differentially expressed proteins identified in this study involved multiple pathways according to the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. Our study provides evidence that some differentially expressed proteins between TAI-positive women and controls were associated with the reproductive process and closely related to important physiologic effects, which could partially explain the underlying mechanism link between TAI and the adverse outcomes of assisted reproductive technology.

The effect of insemination methods on in vitro maturation outcomes

Objective

The aim of this study was to compare the effects of conventional insemination (in vitro fertilization [IVF]) and intracytoplasmic sperm injection (ICSI) on the fertilization, developmental competence, implantation potential, and clinical pregnancy rate of embryos derived from in vitro matured oocytes of patients with polycystic ovary syndrome (PCOS).

Methods

A prospective study was carried out among 38 PCOS patients who had undergone in vitro maturation (IVM) treatment. In total, 828 immature oocytes were collected from 42 cycles and randomly assigned for insemination by IVF (416 oocytes) or ICSI (412 oocytes). After fertilization, the embryos were cultured until the blastocyst stage and single embryos were transferred after endometrial preparation and under ultrasound guidance.

Results

No significant differences were found in the maturation rate (78.1% vs. 72.6% for IVF and ICSI insemination, respectively; p= 0.076), fertilization rate (59.4% vs. 66.9% for IVF and ICSI insemination, respectively; p= 0.063), or the formation of good-quality blastocysts (40.9% vs. 46.5% for IVF and ICSI insemination, respectively; p= 0.314). Implantation and clinical pregnancy also did not show significant differences.

Conclusion

There was a comparable yield of in vitro matured oocytes derived from PCOS patients in terms of fertilization, blastocyst formation, implantation rate, and clinical pregnancy between IVF and ICSI insemination. These findings provide valuable insights for choosing assisted reproductive treatment in women with PCOS, as IVM offers promising outcomes and is less invasive and less costly.

Mammalian egg coat modifications and the block to polyspermy

Fertilization by more than one sperm causes polyploidy, a condition that is generally lethal to the embryo in the majority of animal species. To prevent this occurrence, eggs have developed a series of mechanisms that block polyspermy at the level of the plasma membrane or their extracellular coat. In this review, we first introduce the mammalian egg coat, the zona pellucida (ZP), and summarize what is currently known about its composition, structure, and biological functions. We then describe how this specialized extracellular matrix is modified by the contents of cortical granules (CG), secretory organelles that are exocytosed by the egg after gamete fusion. This process releases proteases, glycosidases, lectins and zinc onto the ZP, resulting in a series of changes in the properties of the egg coat that are collectively referred to as hardening. By drawing parallels with comparable modifications of the vitelline envelope of nonmammalian eggs, we discuss how CG‐dependent modifications of the ZP are thought to contribute to the block to polyspermy. Moreover, we argue for the importance of obtaining more information on the architecture of the ZP, as well as systematically investigating the many facets of ZP hardening.

Multiplex CRISPR/Cas screen in regenerating haploid limbs of chimeric Axolotls

Axolotls and other salamanders can regenerate entire limbs after amputation as adults, and much recent effort has sought to identify the molecular programs controlling this process. While targeted mutagenesis approaches like CRISPR/Cas9 now permit gene-level investigation of these mechanisms, genetic screening in the axolotl requires an extensive commitment of time and space. Previously, we quantified CRISPR/Cas9-generated mutations in the limbs of mosaic mutant axolotls before and after regeneration and found that the regenerated limb is a highfidelity replicate of the original limb (Flowers et al. 2017). Here, we circumvent aforementioned genetic screening limitations and present methods for a multiplex CRISPR/Cas9 haploid screen in chimeric axolotls (MuCHaChA), which is a novel platform for haploid genetic screening in animals to identify genes essential for limb regeneration.

Perfect date-the review of current research into molecular bases of mammalian fertilization

Fertilization is a multistep process during which two terminally differentiated haploid cells, an egg and a sperm, combine to produce a totipotent diploid zygote. In the early 1950s, it became possible to fertilize mammalian eggs in vitro and study the sequence of cellular and molecular events leading to embryo development. Despite all the achievements of assisted reproduction in the last four decades, remarkably little is known about the molecular aspects of human conception. Current fertility research in animal models is casting more light on the complexity of the process all our lives start with. This review article provides an update on the investigation of mammalian fertilization and highlights the practical implications of scientific discoveries in the context of human reproduction and reproductive medicine.

Colorimetric Paper-Based Immunosensor for Simultaneous Determination of Fetuin B and Clusterin toward Early Alzheimer's Diagnosis

Alzheimer's disease is a devastating condition characterized by a progressive and slow brain decay in elders. Here, we developed a paper-based lateral flow immunoassay for simultaneous and fast determination of Alzheimer's blood biomarkers, fetuin B and clusterin. Selective antibodies to targeted biomarkers were immobilized on gold nanoparticles (AuNPs) and deposited on paper pads. After adding the sample on the paper-based device, the biofluid laterally flows toward the selective antibody, permitting AuNP-Ab accumulation on the test zone, which causes a color change from white to pink. Image analysis was performed using a customized algorithm for the automatic recognition of the area of analysis and color clustering. Colorimetric detection was compared to electrochemical methods for the precise quantification of biomarkers. The best performance was found for the color parameter "L*". Good linearity (R² = 0.988 and 0.998) and reproducibility (%RSD = 2.79% and 1.82%, N = 3) were demonstrated for the quantification of fetuin B and clusterin, respectively. Furthermore, the specificity of the immunosensor was tested on mixtures of proteins, showing negligible cross-reactivity and good performance in complex environments. We believe that our biosensor has a potential for early-stage diagnosis of Alzheimer's disease and toward a better understanding of Alzheimer's developing mechanisms.

The C-terminal region of human plasma fetuin-B is dispensable for the raised-elephant-trunk mechanism of inhibition of astacin metallopeptidases

Human fetuin-B plays a key physiological role in human fertility through its inhibitory action on ovastacin, a member of the astacin family of metallopeptidases. The inhibitor consists of tandem cystatin-like domains (CY1 and CY2), which are connected by a linker containing a "CPDCP-trunk" and followed by a C-terminal region (CTR) void of regular secondary structure. Here, we solved the crystal structure of the complex of the inhibitor with archetypal astacin from crayfish, which is a useful model of human ovastacin. Two hairpins from CY2, the linker, and the tip of the "legumain-binding loop" of CY1 inhibit crayfish astacin following the "raised-elephant-trunk mechanism" recently reported for mouse fetuin-B. This inhibition is exerted by blocking active-site cleft sub-sites upstream and downstream of the catalytic zinc ion, but not those flanking the scissile bond. However, contrary to the mouse complex, which was obtained with fetuin-B nicked at a single site but otherwise intact, most of the CTR was proteolytically removed during crystallization of the human complex. Moreover, the two complexes present in the crystallographic asymmetric unit diverged in the relative arrangement of CY1 and CY2, while the two complexes found for the mouse complex crystal structure were equivalent. Biochemical studies in vitro confirmed the differential cleavage susceptibility of human and mouse fetuin-B in front of crayfish astacin and revealed that the cleaved human inhibitor blocks crayfish astacin and human meprin α and β only slightly less potently than the intact variant. Therefore, the CTR of animal fetuin-B orthologs may have a function in maintaining a particular relative orientation of CY1 and CY2 that nonetheless is dispensable for peptidase inhibition.

The molecular mechanisms mediating mammalian fertilization

Fertilization is a key biological process in which the egg and sperm must recognize one another and fuse to form a zygote. Although the process is a continuum, mammalian fertilization has been studied as a sequence of steps: sperm bind and penetrate through the zona pellucida of the egg, adhere to the egg plasma membrane and finally fuse with the egg. Following fusion, effective blocks to polyspermy ensure monospermic fertilization. Here, we review how recent advances obtained using genetically modified mouse lines bring new insights into the molecular mechanisms regulating mammalian fertilization. We discuss models for these processes and we include studies showing that these mechanisms may be conserved across different mammalian species.

Serum and follicular fluid fetuin-B levels are correlated with fertilization rates in conventional IVF cycles

PURPOSE

To investigate the relationship between serum/follicular fluid fetuin-B levels and fertilization outcomes in conventional IVF cycles.

METHODS

A prospective cohort study of conventional IVF treatments including 78 cycles with low fertilization rates (two pronuclei [2PN] rate < 30%; LF group) and 104 cycles performed during the same period with 2PN rate > 70% (high fertilization group, HF). To calculate the required sample size, a two-sample t test power analysis was applied to data from our pilot study, using PASS 11.0 software. Fetuin-B was measured using a commercial sandwich enzyme-linked immunosorbent assay.

RESULTS

Serum fetuin-B and follicular fluid fetuin-B were positively correlated (r = 0.703, P < 0.001). Compared to the HF group, the LF group had significantly lower levels of fetuin-B, both in serum (5.81 ± 1.53 vs. 7.19 ± 1.42, P < 0.001) and follicular fluid (5.06 ± 1.29 vs. 6.16 ± 1.52, P < 0.001). The serum fetuin-B level from cycles with polypronuclear (PPN) zygotes was significantly lower when compared to cycles without PPN zygotes (6.82 ± 1.65 vs. 6.10 ± 1.43, P = 0.006). However, serum fetuin-B level was not correlated with preimplantation embryo development or clinical pregnancy.

CONCLUSION

Serum fetuin-B level is correlated with fertilization rate in conventional IVF and it may be used as a predictive marker of fertilization in IVF treatment.

Structure of mammalian plasma fetuin-B and its mechanism of selective metallopeptidase inhibition

Mammalian fetuin-A and fetuin-B are abundant serum proteins with pleiotropic functions. Fetuin-B is a highly selective and potent inhibitor of metallo-peptidases (MPs) of the astacin family, which includes ovastacin in mammals. By inhibiting ovastacin, fetuin-B is essential for female fertility. The crystal structure of fetuin-B was determined unbound and in complex with archetypal astacin, and it was found that the inhibitor has tandem cystatin-type modules (CY1 and CY2). They are connected by an exposed linker with a rigid, disulfide-linked 'CPDCP-trunk', and are followed by a C-terminal region (CTR) with little regular secondary structure. The CPDCP-trunk and a hairpin of CY2 form a bipartite wedge, which slots into the active-site cleft of the MP. These elements occupy the nonprimed and primed sides of the cleft, respectively, but spare the specificity pocket so that the inhibitor is not cleaved. The aspartate in the trunk blocks the catalytic zinc of astacin, while the CY2 hairpin binds through a QWVXGP motif. The CY1 module assists in structural integrity and the CTR is not involved in inhibition, as verified by in vitro studies using a cohort of mutants and variants. Overall, the inhibition conforms to a novel 'raised-elephant-trunk' mechanism for MPs, which is reminiscent of single-domain cystatins that target cysteine peptidases. Over 200 sequences from vertebrates have been annotated as fetuin-B, underpinning its ubiquity and physiological relevance; accordingly, sequences with conserved CPDCP- and QWVXGP-derived motifs have been found from mammals to cartilaginous fishes. Thus, the raised-elephant-trunk mechanism is likely to be generally valid for the inhibition of astacins by orthologs of fetuin-B.

Mammalian plasma fetuin-B is a selective inhibitor of ovastacin and meprin metalloproteinases

Vertebrate fetuins are multi-domain plasma-proteins of the cystatin-superfamily. Human fetuin-A is also known as AHSG, α₂-Heremans-Schmid-glycoprotein. Gene-knockout in mice identified fetuin-A as essential for calcified-matrix-metabolism and bone-mineralization. Fetuin-B deficient mice, on the other hand, are female infertile due to zona pellucida ‘hardening’ caused by the metalloproteinase ovastacin in unfertilized oocytes. In wildtype mice fetuin-B inhibits the activity of ovastacin thus maintaining oocytes fertilizable. Here we asked, if fetuins affect further proteases as might be expected from their evolutionary relation to single-domain-cystatins, known as proteinase-inhibitors. We show that fetuin-A is not an inhibitor of any tested protease. In stark contrast, the closely related fetuin-B selectively inhibits astacin-metalloproteinases such as meprins and ovastacin, but not astacins of the tolloid-subfamily, nor any other proteinase. The analysis of fetuin-B expressed in various mammalian cell types, insect cells, and truncated fish-fetuin expressed in bacteria, showed that the cystatin-like domains alone are necessary and sufficient for inhibition. This report highlights fetuin-B as a specific antagonist of ovastacin and meprin-metalloproteinases. Control of ovastacin was shown to be indispensable for female fertility. Meprin inhibition, on the other hand, renders fetuin-B a potential key-player in proteolytic networks controlling angiogenesis, immune-defense, extracellular-matrix-assembly and general cell-signaling, with implications for inflammation, fibrosis, neurodegenerative disorders and cancer.

Soma-germ line interactions and a role for muscle in the regulation of C. elegans sperm motility

The development of highly differentiated sperm cells that are specialized for navigating to and fusing with an oocyte is essential for sexual reproduction. As a major part of differentiation, sperm undergo extensive post-meiotic maturation en route to the oocyte. This is regulated largely by soma-derived cues. In Caenorhabditis elegans, this process is called sperm activation, and it transforms immotile spermatids into migratory fertilization-competent cells. Here, we show that the negative regulator of sperm activation, SWM-1, is produced in an unexpected cell type: body wall muscle. SWM-1 is secreted into the body cavity and enters the gonad; there, it is present with its likely target, TRY-5, a spermiogenesis activator. We show that, in addition to SWM-1, the somatic gonad and body fluid can exchange other factors, suggesting that soma-germ line transfer could affect other reproductive processes. In addition, we show that SWM-1 may have a separate role in the sperm migratory environment, to which it is contributed by both males and hermaphrodites. These findings reveal that late stages in gamete differentiation can be regulated at the whole-organism level by broadly secreted factors.This article has an associated 'The people behind the papers' interview.

Intracellular activation of ovastacin mediates pre-fertilization hardening of the zona pellucida

STUDY QUESTION

How and where is pro-ovastacin activated and how does active ovastacin regulate zona pellucida hardening (ZPH) and successful fertilization?

STUDY FINDING

Ovastacin is partially active before exocytosis and pre-hardens the zona pellucida (ZP) before fertilization.

WHAT IS KNOWN ALREADY

The metalloproteinase ovastacin is stored in cortical granules, it cleaves zona pellucida protein 2 (ZP2) upon fertilization and thereby destroys the ZP sperm ligand and triggers ZPH. Female mice deficient in the extracellular circulating ovastacin-inhibitor fetuin-B are infertile due to pre-mature ZPH.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

We isolated oocytes from wild-type and ovastacin-deficient (Astlnull) FVB mice before and after fertilization (in vitro and in vivo) and quantified ovastacin activity and cleavage of ZP2 by immunoblot. We assessed ZPH by measuring ZP digestion time using α-chymotrypsin and by determining ZP2 cleavage. We determined cellular distribution of ovastacin by immunofluorescence using domain-specific ovastacin antibodies. Experiments were performed at least in triplicate with a minimum of 20 oocytes. Data were pre-analyzed using Shapiro-Wilk test. In case of normal distribution, significance was determined via two-sided Student's t-test, whereas in case of non-normal distribution via Mann-Whitney U-test.

MAIN RESULTS AND THE ROLE OF CHANCE

Metaphase II (MII) oocytes contained both inactive pro-ovastacin and activated ovastacin. Immunoblot and ZP digestion assays revealed a partial cleavage of ZP2 even before fertilization in wild-type mice. Partial cleavage coincided with germinal-vesicle breakdown and MII, despite the presence of fetuin-B protein, an endogenous ovastacin inhibitor, in the follicular and oviductal fluid. Upon exocytosis, part of the C-terminal domain of ovastacin remained attached to the plasmalemma, while the N-terminal active ovastacin domain was secreted. This finding may resolve previously conflicting data showing that ovastacin acts both as an oolemmal receptor termed SAS1B (sperm acrosomal SLLP1 binding protein; SLLP, sperm lysozyme like protein) and a secreted protease mediating ZP2 cleavage.

LIMITATIONS, REASONS FOR CAUTION

For this study, only oocytes isolated from wild-type and ovastacin-deficient FVB mice were investigated. Some experiments involved oocyte activation by the Ca2+ ionophore A23187 to trigger ZPH.

WIDER IMPLICATIONS OF THE FINDINGS

This study provides a detailed spatial and temporal view of pre-mature cleavage of ZP2 by ovastacin, which is known to adversely affect IVF rate in mice and humans.

LARGE SCALE DATA

None.

STUDY FUNDING AND COMPETING INTEREST(S)

This work was supported by the Center of Natural Sciences and Medicine and by a start-up grant of the Johannes Gutenberg University Mainz to W.S., and by a grant from Deutsche Forschungsgemeinschaft and by the START program of the Medical Faculty of RWTH Aachen University to J.F. and W.J.D. There are no competing interests to declare.

Viable offspring after imaging of Ca2+ oscillations and visualization of the cortical reaction in mouse eggs

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During mammalian fertilization, egg Ca 2+ oscillations are known to play pivotal roles in triggering downstream events such as resumption of the cell cycle and the establishment of blocks to polyspermy. However, viable offspring have not been obtained after monitoring Ca 2+ oscillations, and their spatiotemporal links to subsequent events are still to be examined. Therefore, the development of imaging methods to avoid phototoxic damage while labeling these events is required. Here, we examined the usefulness of genetically encoded Ca 2+ indicators for optical imaging (GECOs), in combination with spinning-disk confocal imaging. The Ca 2+ imaging of fertilized mouse eggs with GEM-, G-, or R-GECO recorded successful oscillations (8.19 ± 0.31, 7.56 ± 0.23, or 7.53 ± 0.27 spikes in the first 2 h, respectively), similar to those obtained with chemical indicators. Then, in vitro viability tests revealed that imaging with G- or R-GECO did not interfere with the rate of development to the blastocyst stage (61.8 or 70.0%, respectively, vs 75.0% in control). Furthermore, two-cell transfer to recipient female mice after imaging with G- or R-GECO resulted in a similar birthrate (53.3 or 52.0%, respectively) to that of controls (48.7%). Next, we assessed the quality of the cortical reaction (CR) in artificially activated or fertilized eggs using fluorescently labeled Lens culinaris agglutinin fluorescein isothiocyanate. Multicolor imaging demonstrated that the first few Ca 2+ spikes are sufficient for the completion of the CR and subsequent hardening of the zona pellucida in mouse eggs. These methods provide a framework for studying Ca 2+ dynamics in mammalian fertilization.

Profiling of proteins secreted in the bovine oviduct reveals diverse functions of this luminal microenvironment

The oviductal microenvironment is a site for key events that involve gamete maturation, fertilization and early embryo development. Secretions into the oviductal lumen by either the lining epithelium or by transudation of plasma constituents are known to contain elements conducive for reproductive success. Although previous studies have identified some of these factors involved in reproduction, knowledge of secreted proteins in the oviductal fluid remains rudimentary with limited definition of function even in extensively studied species like cattle. In this study, we used a shotgun proteomics approach followed by bioinformatics sequence prediction to identify secreted proteins present in the bovine oviductal fluid (ex vivo) and secretions from the bovine oviductal epithelial cells (in vitro). From a total of 2087 proteins identified, 266 proteins could be classified as secreted, 109 (41%) of which were common for both in vivo and in vitro conditions. Pathway analysis indicated different classes of proteins that included growth factors, metabolic regulators, immune modulators, enzymes, and extracellular matrix components. Functional analysis revealed mechanisms in the oviductal lumen linked to immune homeostasis, gamete maturation, fertilization and early embryo development. These results point to several novel components that work together with known elements mediating functional homeostasis, and highlight the diversity of machinery associated with oviductal physiology and early events in cattle fertility.

Identification and expression analysis of fetuin B (FETUB) in turbot (Scophthalmus maximus L.) mucosal barriers following bacterial challenge

Fetuin B (FETUB), a recently described cysteine proteinase inhibitor, has numerous conserved N-glycosylation sites, species-specific O-glycosylation sites, and two cystatin (CY) domains. FETUB is likely to play regulatory roles in acute inflammation, female infertility, fish organogenesis and tumor suppression. In the present study, transcript of turbot FETUB gene was captured, its protein structure and expression patterns in different tissues with emphasis on mucosal barriers following different bacterial infection were characterized. Turbot FETUB gene showed the closest relationship with Takifugu rubripes in phylogenetic analysis. In addition, FETUB was ubiquitously expressed in all examined tissues with the highest expression level in skin. Finally, FETUB gene showed different expression patterns following both bacterial challenge. The rapidly and significantly differential expression patterns of FETUB in mucosal surfaces against bacterial infections might indicate its key roles to prevent pathogen attachment and entry in turbot mucosal immunity. Functional studies should be carried out to further characterize the FETUB and avail utilization of its function to increase the disease resistance of turbot in maintaining the integrity of the mucosal barriers against infections and to facilitate selection of the fine family/varieties of disease resistance in turbot.

Identification and characterization of secreted factors that are upregulated during somatic cell reprogramming

The process of cell reprogramming has been characterized considerably since the successful generation of induced pluripotent stem cells. However, the importance of cell-cell communications for cellular reprogramming remains largely unknown. Secreted factors, which are expressed and secreted during reprogramming, may influence the reprogramming efficiency. Here, we have identified Sostdc1, Glb1l2, Fetub, Dpp4, Gdf3, Trh, and Tdgf1 as prominently upregulated secreted factors during reprogramming. Our detailed analysis reveals that these seven factors may be categorized into four groups based on their expression patterns in relation to the reprogramming stages. Remarkably, knockdown of Sostdc1, which is the most prominently upregulated factor and which is expressed earlier than the other six factors, results in reduced reprogramming efficiency, suggesting its involvement in the reprogramming process.

Protein-drug nanoconjugates: Finding the alternative proteins as drug carrier

Present study was conducted to establish the interaction of bovine fetuin-A to validate its binding modalities with doxorubicin (Dox). Fetuin-A was purified to highest purity and monodispersity. Green synthesis of fetuin-A conjugated gold nanoparticles (F-GNPs) has been performed giving typical UV-maxima with subtle variation in fourier transform infrared spectroscopy (FTIR). Atomic force microscopy (AFM) revealed spherical shaped, polydisperse F-GNPs of varying sizes, complementing the radius of hydration (19.5-62.4nm) by dynamic light scattering (DLS). Circular dichroism (CD) analysis of fetuin-A with respect to Dox interaction shows remarkable reduction in ellipticity with increasing concentrations of Dox (20-120μM). Fetuin-A:Dox and F-GNPs:Dox at variable concentrations revealed significantly enhanced absorption spectra, while a continuous decrease in florescence (560nm). This effect was more drastic when Dox interact with fetuin-A as compared to F-GNPs. Some known antimicrobial drugs were also investigated under similar conditions, giving strong quenching effect in a dose dependent manner suggesting the significant yet differential interactions. In cytotoxicity assay, fetuin-A:Dox conjugates revealed less toxicity as compared to F-GNPs:Dox and Dox alone. In-silico studies of the fetuin-A:Dox complex suggest that the drug binds in the major grove between beta-sheet and long loop region of D1 domain and stabilized by several hydrogen bonds.