A mouse sperm decapacitation factor receptor is phosphatidylethanolamine-binding protein 1

Comparative iTRAQ proteomics identified proteins in fresh and frozen thawed yak spermatozoa

The changes in semen and cryodamage after the cryopreservation process negatively affect sperm function and motility. However, possible proteomic alterations of yak semen during cryopreservation have not yet been achieved. In this study, we compared proteomes of fresh and frozen thawed yak sperm using iTRAQ combined with LC-MS/MS proteome approach. Totally, 2064 proteins were quantitatively identified, including 161 in fresh sperm that showed significant differences compared to frozen thawed sperm. According to the Gene ontology (GO) enrichment analysis, differentially expressed proteins (DEPs) are predominantly associated with spermatogenesis, tricarboxylic acid cycle, ATP synthesis, and differentiation biological process. Furthermore, the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that DEPs were mainly involved in metabolic pathways related to pyruvate metabolism, carbon metabolism, glycolysis/gluconeogenesis, together with the citrate (TCA) cycle. In the analysis of the protein-protein interaction (PPI) network, 15 potential proteins (PDHB, DLAT, PDHA2, PGK1, TP5C1, etc.) that could be related to the sperm quality of the yaks were obtained. Furthermore, 6 DEPs were validated by parallel reaction monitoring (PRM), confirming that the iTRAQ data were reliable. These results indicate that cryopreservation alters the proteome of yak sperm, which is possibly related to cryodamage and fertilization ability.

The Proteome of Large or Small Extracellular Vesicles in Pig Seminal Plasma Differs, Defining Sources and Biological Functions

Seminal plasma contains many morphologically heterogeneous extracellular vesicles (sEVs). These are sequentially released by cells of the testis, epididymis, and accessory sex glands and involved in male and female reproductive processes. This study aimed to define in depth sEV subsets isolated by ultrafiltration and size exclusion chromatography, decode their proteomic profiles using liquid chromatography-tandem mass spectrometry, and quantify identified proteins using sequential window acquisition of all theoretical mass spectra. The sEV subsets were defined as large (L-EVs) or small (S-EVs) by their protein concentration, morphology, size distribution, and EV-specific protein markers and purity. Liquid chromatography-tandem mass spectrometry identified a total of 1034 proteins, 737 of them quantified by SWATH in S-EVs, L-EVs, and non-EVs-enriched samples (18-20 size exclusion chromatography-eluted fractions). The differential expression analysis revealed 197 differentially abundant proteins between both EV subsets, S-EVs and L-EVs, and 37 and 199 between S-EVs and L-EVs versus non-EVs-enriched samples, respectively. The gene ontology enrichment analysis of differentially abundant proteins suggested, based on the type of protein detected, that S-EVs could be mainly released through an apocrine blebbing pathway and be involved in modulating the immune environment of the female reproductive tract as well as during sperm-oocyte interaction. In contrast, L-EVs could be released by fusion of multivesicular bodies with the plasma membrane becoming involved in sperm physiological processes, such as capacitation and avoidance of oxidative stress. In conclusion, this study provides a procedure capable of isolating subsets of EVs from pig seminal plasma with a high degree of purity and shows differences in the proteomic profile between EV subsets, indicating different sources and biological functions for the sEVs.

Transcriptomic landscape of GC-2spd(ts) cell in response to the downregulation of piR-1207/2107

Spermatogenesis is a highly orchestrated dynamic developmental process, during which piRNAs play an indispensable role. Our previous studies have confirmed that the levels of piR-1207 and piR-2107 were significantly decreased in spermatozoa and seminal plasma of patients with asthenozoospermia, compared with the fertile controls. In order to explore the function of piR-1207 and piR-2107 in human spermatogenesis and their potential regulatory downstream genes, we examined the transcriptomic landscape in mouse spermatocyte cell line GC-2spd(ts) transfected with anti-piR-1207 and anti-piR-2107 by RNA sequencing. The result showed that 86 and 75 differential expression genes (DEGs) in anti-piR-1207 and anti-piR-2107 group, respectively. Among the DEGs, three genes including Pbp2, Pde3a and Cage1 were identified as potential key genes playing important roles in mediating sperm motility and morphology in anti-piR-1207 or anti-piR-2107 transfected transcriptomic response. Next, the expression levels of Pbp2, Pde3a and Cage1 were confirmed by qRT-PCR. These results showed that Pbp2, Pde3a and Cage1 may serve as the potential regulatory genes of piR-1207 or piR-2107. In summary, piR-1207 and piR-2107 might have an implication in modulating the process of spermatogenesis through regulating the expression of potential genes.

Proteomic analysis of spermatozoa reveals caseins play a pivotal role in preventing short-term periods of subfertility in stallions

Stallions experience transient fluctuations in fertility throughout the breeding season. Considering pregnancy diagnoses cannot be ascertained until ~14 days post-breeding, the timely detection of decreases in stallion fertility would enhance industry economic and welfare outcomes. Therefore, this study aimed to identify the proteomic signatures reflective of short-term fertility fluctuations, and to determine the biological mechanisms governing such differences. Using LC–MS/MS, we compared the proteomic profile of semen samples collected from commercially “fertile” stallions, during high- and low-fertility periods. A total of 1702 proteins were identified, of which, 38 showed a significant change in abundance (p ≤ 0.05). Assessment of intra- and inter-stallion variability revealed that caseins (namely κ-, α-S1-, and α-S2-casein), were significantly more abundant during “high-fertility” periods, while several epididymal, and seminal plasma proteins (chiefly, epididymal sperm binding protein 1 [ELSPbP1], horse seminal plasma protein 1 [HSP-1] and clusterin), were significantly more abundant during “low-fertility” periods. We hypothesised that an increased abundance of caseins offers greater protection from potentially harmful seminal plasma proteins, thereby preserving cell functionality and fertility. In vitro exposure of spermatozoa to casein resulted in decreased levels of lipid scrambling (Merocyanine 540), higher abundance of sperm-bound caseins (α-S1-, α-S2-, and κ-casein), and lower abundance of sperm-bound HSP-1 (p ≤ 0.05). This study demonstrates key pathways governing short-term fertility fluctuations in the stallion, thereby providing a platform to develop robust, fertility assessment strategies into the future.

Transcriptional regulation of PEBP1 expression by androgen receptor in mouse testes

Androgen and AR are essential for maintaining spermatogenesis and male fertility. Previous studies have shown that the phosphatidyl ethanolamine binding protein 1 (Pebp1) gene is down-regulated in the selective ablation of the AR in the Sertoli cells of mouse testes compared with wild-type mice, indicating that Pebp1 is a candidate target of AR. The ChIP-PCR data and ChIP-sequencing results of this study verified that Pebp1 is a target gene regulated by AR. Real-time PCR, Western blot analysis, and immunofluorescence data showed that Pebp1 is expressed at all stages of testicular development, with an increasing trend from 1 to 8 weeks of postnatal development. PEBP1 was principally located in the cytoplasm, and high-intensity fluorescence revealed PEBP in the lumen of the testicular tubules. Bioinformatics analysis indicated effective androgen-responsive elements (AREs) located in the promotor of Pepb1 gene. Dual fluorescence assay data showed that androgens and AR could bind to the AREs of Pebp1 and induce an increase of gene expression. These data suggest that Pepb1 is a newfound target gene regulated by androgens and AR in mouse Sertoli cells. However, the detailed molecular mechanism of their role in spermatogenesis still needs to be further studied.Abbreviations: AR: androgen receptor; Pebp1: phosphatidyl ethanolamine binding protein 1; ARKO: androgen receptor knockout; WT: wild type; SCARKO: Sertoli cell-selective androgen receptor knockout; ChIP: chromatin immunoprecipitation; RKIP: Raf kinase inhibitory protein; MAPK: mitogen-activated protein kinase; NF-κB: nuclear factor kappa-light-chain-enhancer of activated B cells; GSK-3: glycogen synthase kinase-3; RT-PCR: reverse transcriptase polymerase chain reaction; SEM: standard error of the mean.

Sperm Functional Genome Associated With Bull Fertility

Bull fertility is an important economic trait in sustainable cattle production, as infertile or subfertile bulls give rise to large economic losses. Current methods to assess bull fertility are tedious and not totally accurate. The massive collection of functional data analyses, including genomics, proteomics, metabolomics, transcriptomics, and epigenomics, helps researchers generate extensive knowledge to better understand the unraveling physiological mechanisms underlying subpar male fertility. This review focuses on the sperm phenomes of the functional genome and epigenome that are associated with bull fertility. Findings from multiple sources were integrated to generate new knowledge that is transferable to applied andrology. Diverse methods encompassing analyses of molecular and cellular dynamics in the fertility-associated molecules and conventional sperm parameters can be considered an effective approach to determine bull fertility for efficient and sustainable cattle production. In addition to gene expression information, we also provide methodological information, which is important for the rigor and reliability of the studies. Fertility is a complex trait influenced by several factors and has low heritability, although heritability of scrotal circumference is high and that it is a known fertility maker. There is a need for new knowledge on the expression levels and functions of sperm RNA, proteins, and metabolites. The new knowledge can shed light on additional fertility markers that can be used in combination with scrotal circumference to predict the fertility of breeding bulls. This review provides a comprehensive review of sperm functional characteristics or phenotypes associated with bull fertility.

The current perspective on genetic and epigenetic factors in sperm maturation in the epididymis

Male infertility affects approximately 30% of infertile couples. As spermatozoa mature in the epididymal lumen, their potential for mobility increases, and their protein, lipid and small RNA (sRNA) content changes, whereas capacitation and fertilisation take place in the female reproductive tract. Both of the latter processes are affected by maturation, because impaired maturation causes premature capacitation and fertilization. The epididymis produces a suitable environment for sperm maturation via ion transport, vesicle secretion and protein matrix formation. The microenvironment for sperm maturation varies in three broad segments: the caput, the corpus and the cauda epididymis. Epididymosomes transfer proteins, lipids and sRNAs from the epididymal epithelium to spermatozoa and genetic alterations of epididymal genes can lead to decreased sperm motility, morphological abnormalities of spermatozoa and subfertility. Genetic factors are involved in all aetiological categories in male infertility. However, studies conducted on the genes involved in epididymal functions are limited. The sRNA content of spermatozoa changes during epididymal migration, and these sRNAs play a role in embryo development and epigenetic inheritance. This review aims to clarify the role of the epididymal epithelium in the maturation of spermatozoa in light of the current molecular genomic knowledge.

Extracellular Vesicles and the Oviduct Function

In mammals, the oviduct (or the Fallopian tube in humans) can be divided into the infundibulum (responsible for oocyte pick-up), ampulla (site of fertilization), isthmus (where preimplantation embryos develop), and uterotubal junction (where embryos transit to the uterus). The oviductal fluid, as well as extracellular vesicles produced from the oviduct epithelial cells, referred to as oEVs, have been shown to improve the fertilization process, prevent polyspermy, and aid in embryo development. oEVs contain molecular cargos (such as miRNAs, mRNAs, proteins, and lipids) that can be delivered and fuse to recipient cells. oEVs produced from the ampulla appear to be functionally distinct from those produced from the isthmus. In multiple species including mice, cats, dogs, pigs, and cows, oEVs can be incorporated into the oocytes, sperm, and embryos. In this review, we show the positive impact of oEVs on gamete function as well as blastocyst development and how they may improve embryo quality in in vitro conditions in an assisted reproductive technology setting for rodents, domestic animals, farm animals, and humans.

Transcriptome analysis of the epididymis from Plag1 deficient mice suggests dysregulation of sperm maturation and extracellular matrix genes

BACKGROUND

The transcription factor pleomorphic adenoma gene 1 (PLAG1) is required for male fertility. Mice deficient in PLAG1 exhibit decreased sperm motility and abnormal epididymal tubule elongation and coiling, indicating impaired sperm maturation during epididymal transit. However, the downstream transcriptomic profile of the Plag1 knockout (KO; Plag1^-/- ) murine epididymis is currently unknown.

RESULTS

In this study, the PLAG1-dependent epididymal transcriptome was characterised using RNA sequencing. Several genes important for the control of sperm maturation, motility, capacitation and the acrosome reaction were dysregulated in Plag1^-/- mice. Surprisingly, several cell proliferation genes were upregulated, and Ki67 analysis indicated that cell proliferation is aberrantly upregulated in the cauda epididymis stroma of Plag1^-/- mice. Gene ontology analysis showed an overall upregulation of genes encoding extracellular matrix components, and an overall downregulation of genes encoding metalloendopeptidases in the epididymides from Plag1^-/- mice.

CONCLUSION

Together, these results suggest a defect in the epididymal extracellular matrix in Plag1^-/- mice. These results imply that in addition to maintaining epididymal integrity directly, PLAG1 may also regulate several genes involved in the regulation of sperm maturation and capacitation. Moreover, PLAG1 may also be involved in regulating tissue homeostasis and ensuring proper structure and maintenance of the extracellular matrix in the epididymis.

Functional analysis and characterization of antimicrobial phosphatidylethanolamine-binding protein BmPEBP in the silkworm Bombyx mori

Phosphatidylethanolamine-binding proteins (PEBPs) are a class of highly conserved, biologically diverse proteins, which are widely distributed in plants, insects, and mammals. In this study, a Bombyx mori PEBP (BmPEBP) gene was reported, which encodes a protein composed of 209 amino acid residues. BmPEBP includes a predicted signal peptide, indicating that it is an extracellular protein, which differs from the cytoplasmic PEBPs of plants and mammals. Recombinant soluble BmPEBP was successfully synthesized using a prokaryotic expression system and was then purified effectively by Ni²⁺-NTA affinity chromatography and gel filtration. Far-ultraviolet circular dichroism spectra indicated that BmPEBP had a well-defined β-sheet structure, with the β-sheet content accounting for about 41% of the protein. BmPEBP had a relatively stable structure at temperatures ranging from 15 °C to 57.5 °C. The Tm, ΔH, and ΔS of BmPEBP were 62.27 °C ± 0.14 °C, 570.10 ± 0.17 kJ/mol, and 1.70 ± 0.03 KJ/(mol·K), respectively. Homology modeling analysis suggested that the active sites of BmPEBP were conserved, comprising Pro96, His111, and His143. Quantitative real-time PCR showed that BmPEBP was highly expressed in the silk gland and had very low expression in other tissues. However, BmPEBP expression was significantly upregulated in the larval fat body after infection with two kinds of fungi, Beauveria bassiana and Candida albicans. Moreover, in vitro fungal inhibition tests showed that BmPEBP could significantly inhibit the sporular growth of Saccharomyces cerevisiae, C. albicans, B. bassiana, and Aspergillus fumigatus. To our knowledge, this is the first report to reveal the antifungal role of a PEBP in insects.

Progesterone alters the bovine uterine fluid lipidome during the period of elongation

Successful bovine pregnancy establishment hinges on conceptus elongation, a key reproductive phenomenon coinciding with the period during which most pregnancies fail. Elongation is yet to be recapitulated in vitro, whereas in vivo it is directly driven by uterine secretions and indirectly influenced by prior circulating progesterone levels. To better understand the microenvironment evolved to facilitate this fundamental developmental event, uterine fluid was recovered on Days 12–14 of the oestrous cycle – the window of conceptus elongation initiation – from cycling heifers supplemented, or not, with progesterone. Subsequent lipidomic profiling of uterine luminal fluid by advanced high-throughput metabolomics revealed the consistent presence of 75 metabolites, of which 47% were intricately linked to membrane biogenesis, and with seven displaying a day by progesterone interaction (P ≤ 0.05). Four metabolic pathways were correspondingly enriched according to day and P4 – i.e. comprised metabolites whose concentrations differed between groups (normal vs high P4) at different times (Days 12 vs 13 vs 14). These were inositol, phospholipid, glycerolipid and primary bile acid metabolism. Moreover, P4 elevated total uterine luminal fluid lipid content on Day 14 (P < 0.0001) relative to all other comparisons. The data combined suggest that maternal lipid supply during the elongation-initiation window is primarily geared towards conceptus membrane biogenesis. In summary, progesterone supplementation alters the lipidomic profile of bovine uterine fluid during the period of conceptus elongation initiation.

Proteins from male and female reproductive tracts involved in sperm function regulation

Spermatogenesis is a dynamic process that culminates in the production of mature spermatozoa in the seminiferous tubules of sexually mature animals. Although sperm leaving the testis are fully differentiated, they must further undergo two additional maturation steps before acquiring the capability to fertilize the egg. Such processes take place during the epididymal residency and transport in the seminal fluid during ejaculation and, after delivery into the female reproductive tract, during the journey aiming the encountering the egg in the oviduct. Throughout this trip, spermatozoa are exposed to different reproductive fluids whose molecular compositions regulate the progress towards obtaining a fertilized competent cell. This review summarizes the evidence obtained so far supporting the participation of male and female reproductive tract-derived proteins in the modulation of sperm fertilizing ability and discusses the mechanisms by which such regulation may be accomplished.

Gynura procumbens Improved Fertility of Diabetic Rats: Preliminary Study of Sperm Proteomic

Gynura procumbens (GP) is a medicinal herb that has long been known as anti-inflammatory and antihyperglycaemic. Recently, this herbal extract has been associated with a profertility effect, suggesting its applicability in treating both diabetes and male infertility. In this study, the effects of GP aqueous extract (GPAE) on diabetic rats were investigated through evaluating testes histology and androgen hormone levels as well as the implantation sites of female rats on copulation with the treated male rats. Three dosages of GPAE were used (150, 300, and 450 mg/kg), and there were three control groups [normal, diabetic, and metformin-treated diabetic]. Testes histology, androgen hormone levels, and number of implantation sites of the GPAE-treated groups matched those of the normal group in contrast to the diabetic and metformin-treated diabetic controls. Sperm proteomics analysis identified 666 proteins, but only 88 were consistently found in all the control and 450-mg/kg GPAE-treated groups. Four proteins, including cysteine-rich secretory protein 1, carboxylesterase 5A, zona pellucida binding protein, and phosphatidylethanolamine-binding protein 1, were significantly upregulated with GPAE treatment compared with the diabetic control, matching the protein levels of the normal group. These proteins were mainly involved in sperm maturation, sperm capacitation, and sperm-egg interaction, suggesting that GP treatment was able to restore the fertility of male diabetic rats at molecular protein level. In conclusion, GP treatment effectively treats infertility of male diabetic rats, possibly through the upregulation of proteins related to sperm maturation and sperm-egg interaction.

Feedback regulation of RTK signaling in development

Precise regulation of the amplitude and duration of receptor tyrosine kinase (RTK) signaling is critical for the execution of cellular programs and behaviors. Understanding these control mechanisms has important implications for the field of developmental biology, and in recent years, the question of how augmentation or attenuation of RTK signaling via feedback loops modulates development has become of increasing interest. RTK feedback regulation is also important for human disease research; for example, germline mutations in genes that encode RTK signaling pathway components cause numerous human congenital syndromes, and somatic alterations contribute to the pathogenesis of diseases such as cancers. In this review, we survey regulators of RTK signaling that tune receptor activity and intracellular transduction cascades, with a focus on the roles of these genes in the developing embryo. We detail the diverse inhibitory mechanisms utilized by negative feedback regulators that, when lost or perturbed, lead to aberrant increases in RTK signaling. We also discuss recent biochemical and genetic insights into positive regulators of RTK signaling and how these proteins function in tandem with negative regulators to guide embryonic development.

Transcript expression bias of phosphatidylethanolamine binding protein gene in bumblebee, Bombus lantschouensis (Hymenoptera: Apidae)

The phosphatidylethanolamine-binding protein (PEBP) family is a highly conserved group of proteins found in a wide range of organism. It plays an important role in innate immunity of insects. Little is known on the expression characteristic and function of PEBP in bees. In the current study, we cloned the pebp gene and investigated its expression profiles at different developmental stages and reproductive status from bumblebee, Bombus lantschouensis (Vogt), which is one of the most abundant pollinators for wild plants and crops in Northern China. Two transcripts (PEBPX1 and PEBPX2) of the pebp gene were cloned for the first time. The transcript PEBPX2 lacked a signal peptide sequence compared to PEBPX1. The full-length cDNA of these two PEBP transcripts is 1005bp and 915bp, with an open reading frame of 627bp and 549bp, respectively. Transcript PEBPX2 was one order of magnitude more expressed than transcript PEBPX1 at most of the developmental stages and different reproductive status (egg-laying versus non- egg-laying females). Both of the PEBP transcripts were highly expressed in brown-eyed with light and dark pigmented cuticle pupae stages. Quantitative PCR and Western Blot demonstrated that PEBP was significantly up-regulated in egg-laying females. In summary, we suggest that levels of these two PEBPs could be related to the regulation of reproduction in bumblebees. In addition, both transcripts likely play an important role in the metamorphosis developmental stage of bumblebee pupae.

Regulation of the bovine oviductal fluid proteome

Our objective was to investigate the regulation of the proteome in the bovine oviductal fluid according to the stage of the oestrous cycle, to the side relative to ovulation and to local concentrations of steroid hormones. Luminal fluid samples from both oviducts were collected at four stages of the oestrous cycle: pre-ovulatory (Pre-ov), post-ovulatory (Post-ov), and mid- and late luteal phases from adult cyclic cows (18–25 cows/stage). The proteomes were assessed by nanoLC–MS/MS and quantified by label-free method. Totally, 482 proteins were identified including a limited number of proteins specific to one stage or one side. Proportions of differentially abundant proteins fluctuated from 10 to 24% between sides at one stage and from 4 to 20% among stages in a given side of ovulation. In oviductal fluids ipsilateral to ovulation, Annexin A1 was the most abundant protein at Pre-ov compared with Post-ov while numerous heat shock proteins were more abundant at Post-ov compared with Pre-ov. Among differentially abundant proteins, seven tended to be correlated with intra-oviductal concentrations of progesterone. A wide range of biological processes was evidenced for differentially abundant proteins, of which metabolic and cellular processes were predominant. This work identifies numerous new candidate proteins potentially interacting with the oocyte, spermatozoa and embryo to modulate fertilization and early embryo development.

Regulation of Sperm Capacitation by the 26S Proteasome: An Emerging New Paradigm in Spermatology

The ubiquitin proteasome system (UPS) participates in many biological processes ranging from cell cycle and antigen processing to cellular defense and signaling. Work of the last decade has made it evident that the UPS is involved in many sperm-related processes leading up to and as part of fertilization. The current knowledge of UPS involvement and changes during sperm capacitation are reviewed together with a list of known proteasome-associated sperm proteins and a discussion of the relationships between these proteins and the proteasome. Proteasomal inhibitors such as MG-132 and epoxomicin significantly alter capacitation and prevent acrosome reaction. The 26S proteasome degrades AKAP3, an A-kinase anchoring protein, partially regulating the release of protein-kinase A (PKA), a vital component necessary for the steps leading up to capacitation. Further, changes occur in 20S core subunit localization and abundance throughout capacitation. Proteasome-interacting valosine-containing protein (VCP) undergoes tyrosine phosphorylation; however, its physiological roles in capacitation and fertilization remain unknown. The E1-type ubiquitin-activating enzyme (UBA1) inhibitor PYR-41 also alters acrosomal membrane remodeling during capacitation. Furthermore, after capacitation, the acrosomal proteasomes facilitate the degradation of zona pellucida glycoproteins leading up to fertilization. Methods to modulate the sperm proteasome activity during sperm storage and capacitation may translate to increased reproductive efficiency in livestock animals. Human male infertility diagnostics may benefit from incorporation of research outcomes built upon relationships between UPS and capacitation. Altogether, the studies reviewed here support the involvement of UPS in sperm capacitation and present opportunities for new discoveries.

Role of epididymal anti sticking factor in sperm capacitation

Sperm capacitation depends on several features like hormones, ions, intracellular signaling, sperm associated molecules, etc. Anti sticking factor (ASF) is a novel sperm surface associated glycoprotein isolated from epididymal plasma. Function of ASF in vivo has not been revealed yet. The current study is an attempt to highlight the surface localization of ASF and corresponding biochemical changes that occurs in sperm cells during in vitro capacitation. In the presence of 1 nM ASF, percentage of bicarbonate and BSA induced capacitated cells in modified Tyrode medium (7.2) decreased from 72.45% to 16.25% as per Merocyanine 540 (M540)/DAPI stained flowcytometric analysis. Indirect immunocytostaining and western blot analysis shows that the amount of sperm surface bound residual ASF decline during in vitro capacitation. ASF at its effective concentrations notably reduced the bicarbonate and BSA induced cholesterol efflux. These data help in concluding ASF as a majorly responsible molecule that maintains caprine sperm membrane integrity by inhibiting cholesterol efflux. As the capacitation process, progress at in vitro condition, ASF is found to be released from the sperm surface and cell moved from non-capacitated to the capacitated state.

Disruption of murine Tcte3-3 induces tissue specific apoptosis via co-expression of Anxa5 and Pebp1

Programmed cell death or apoptosis plays a vital physiological role in the development and homeostasis. Any discrepancy in apoptosis may trigger testicular and neurodegenerative diseases, ischemic damage, autoimmune disorders and many types of cancer. Tcte3 (T-complex testis expressed 3) is an accessory component of axonemal and cytoplasmic dynein which expresses predominantly in meiotic and postmeiotic germ cells. It plays an essential role during spermatogenesis; however, to explore its diverse and complex functioning in male germ cell apoptosis, requires further prosecution. Here, 2D-gel electrophoresis, mass spectrometry and qRT-PCR analyses were performed to elucidate the differential expression of genes, in both wild-type and homozygous Tcte3-3 mice. We observed an increased expression of Tcte3 in homozygotes as compared to wild-type testes. Perpetually, an increased expression of Anxa5 and Pebp1, while a lower expression of Rsph1 was detected in Tcte3-3^-/- mice. We propose that over-expression of Pebp1 and Anxa5 in Tcte3-3^-/- testes might be due to increased apoptosis. To evaluate this possibility, testes specific microarray data set extracted from NCBI gene ontology omnibus (GEO) was used to cluster the possible co-expression partners of Tcte3. Further functional coherence of compiled candidate genes was monitored computationally by studying the common TFBS overlapped at the regulatory regions. Differential expression of Tcte3-3 and its involvement in apoptosis may provide a basis for the investigation of transcriptional specificities of other Tcte3 paralogs (Tcte3-1 and Tcte3-2). A complete understanding of controlling factors which have implications in regulating tissue-specific Tcte3 expression would provide additional insights into the gene control events. The collective knowledge may prove useful for the development of novel therapeutic regimen and would open new avenues in defining selective roles of Tcte3 in germ cell development.

Post-testicular sperm maturation and identification of an epididymal protein in the Japanese quail (Coturnix coturnix japonica)

The role of the avian epididymis in post-testicular development and capacitation was examined to assess whether avian spermatozoa undergo any processes similar to those characteristic of mammalian sperm development. We found no evidence of a need for quail sperm to undergo capacitation and 90% of testicular sperm could bind to a perivitelline membrane and acrosome react. However, computer-assisted sperm analysis showed that 20% of testicular sperm from the quail were capable of movement and only about 12% of the motile sperm would have a curvilinear velocity greater than the mean for sperm from the distal epididymis. Nevertheless, epididymal transit was associated with increases in mean sperm velocity and the proportion of motile sperm. Together, these findings explain why earlier workers have achieved some fertilizations following inseminations of testicular spermatozoa and also demonstrate the need for some epididymal maturation of avian spermatozoa. Analysis of the electrophoretic profile of quail epididymal luminal proteins revealed that only one major protein (∼16 kDa) is secreted by the epididymis and it was virtually the only protein secreted by the ipsilateral epididymis following unilateral orchidectomy. Mass spectrometry showed that this protein is hemoglobin; this finding was confirmed using anti-hemoglobin antibodies. It is suggested that hemoglobin may support sperm metabolism in the quail epididymis, aid in motility, and/or serve as an antioxidant.

Sperm and seminal fluid proteomes of the field cricket Teleogryllus oceanicus: identification of novel proteins transferred to females at mating

Reproductive proteins are amongst the most evolutionarily divergent proteins known, and research on genetically well-characterized species suggests that postcopulatory sexual selection might be important in their evolution; however, we lack the taxonomic breadth of information on reproductive proteins that is required to determine the general importance of sexual selection for their evolution. We used transcriptome sequencing and proteomics to characterize the sperm and seminal fluid proteins of a cricket, Teleogryllus oceanicus, that has been widely used in the study of postcopulatory sexual selection. We identified 57 proteins from the sperm of these crickets. Many of these had predicted function in glycolysis and metabolism, or were structural, and had sequence similarity to sperm proteins found across taxa ranging from flies to humans. We identified 21 seminal fluid proteins, some of which resemble those found to be involved in postmating changes to female reproduction in other species. Some 27% of sperm proteins and 48% of seminal fluid proteins were of unknown function. The characterization of seminal fluid proteins in this species will allow us to explore their adaptive significance, and to contribute comparative data that will facilitate a general appreciation of the evolution of reproductive proteins within and among animal taxa.

Sperm surface changes and physiological consequences induced by sperm handling and storage

Spermatozoa interact with their immediate environment and this contact remodels the sperm surface in preparation for fertilisation. These fundamental membrane changes will be critically covered in this review with special emphasis on the very specific surface destabilisation event, capacitation. This process involves very subtle and intricate modifications of the sperm membrane including removal of suppression (decapacitation) factors and changes in the lateral organisation of the proteins and lipids of the sperm surface. Processing of sperm for assisted reproduction (storage, sex-sorting, etc.) subjects spermatozoa to numerous stressors, and it is possible that this processing overrides such delicate processes resulting in sperm instability and cell damage. To improve sperm quality, novel mechanisms must be used to stabilise the sperm surface during handling. In this review, different types of membrane stress are considered, as well as novel surface manipulation methods to improve sperm stability.

Structural remodeling, trafficking and functions of glycosylphosphatidylinositol-anchored proteins

Glycosylphosphatidylinositol (GPI) is a glycolipid that is covalently attached to proteins as a post-translational modification. Such modification leads to the anchoring of the protein to the outer leaflet of the plasma membrane. Proteins that are decorated with GPIs have unique properties in terms of their physical nature. In particular, these proteins tend to accumulate in lipid rafts, which are critical for the functions and trafficking of GPI-anchored proteins (GPI-APs). Recent studies mainly using mutant cells revealed that various structural remodeling reactions occur to GPIs present in GPI-APs as they are transported from the endoplasmic reticulum to the cell surface. This review examines the recent progress describing the mechanisms of structural remodeling of mammalian GPI-anchors, such as inositol deacylation, glycan remodeling and fatty acid remodeling, with particular focus on their trafficking and functions, as well as the pathogenesis involving GPI-APs and their deficiency.

Cellular mechanisms regulating sperm-zona pellucida interaction

For mammalian spermatozoa to exhibit the ability to bind the zona pellucida (ZP) they must undergo three distinct phases of maturation, namely, spermatogenesis (testis), epididymal maturation (epididymis) and capacitation (female reproductive tract). An impressive array of spermatozoa surface remodeling events accompany these phases of maturation and appear critical for recognition and adhesion of the outer vestments of the oocyte, a structure known as the ZP. It is becoming increasingly apparent that species-specific zona adhesion is not mediated by a single receptor. Instead, compelling evidence now points toward models implicating a multiplicity of receptor-ligand interactions. This notion is in keeping with emerging research that has shown that there is a dynamic aggregation of proteins believed to be important in sperm-ZP recognition to the regions of sperm that mediate this binding event. Such remodeling may in turn facilitate the assembly of a multimeric zona recognition complex (MZRC). Though formation of MZRCs raises questions regarding the nature of the block to polyspermy, formation and assembly of such a structure would no doubt explain the strenuous maturation process that sperm endure on their sojourn to functional maturity.

Post testicular sperm maturational changes in the bull: important role of the epididymosomes and prostasomes

After spermatogenesis, testicular spermatozoa are not able to fertilize an oocyte, they must undergo sequential maturational processes. Part of these essential processes occurs during the transit of the spermatozoa through the male reproductive tract. Since the sperm become silent in terms of translation and transcription at the testicular level, all the maturational changes that take place on them are dependent on the interaction of spermatozoa with epididymal and accessory gland fluids. During the last decades, reproductive biotechnologies applied to bovine species have advanced significantly. The knowledge of the bull reproductive physiology is really important for the improvement of these techniques and the development of new ones. This paper focuses on the importance of the sperm interaction with the male reproductive fluids to acquire the fertilizing ability, with special attention to the role of the membranous vesicles present in those fluids and the recent mechanisms of protein acquisition during sperm maturation.

A transcriptional element of the diapause program in the Asian tiger mosquito, Aedes albopictus, identified by suppressive subtractive hybridization

Many temperate insects cope with the unfavorable conditions of winter by entering a photoperiodic diapause, but the molecular basis of this crucial adaptation is not well understood. In temperate populations of Aedes albopictus, exposure to short-day lengths causes the adult female to oviposit diapausing eggs. Suppressive subtractive hybridization (SSH) and quantitative reverse transcription PCR (qRT-PCR) were performed on RNA isolated from mature (stage V) oocytes of a temperate population of Ae. albopictus. A total of 438 inserts were sequenced from the SSH library and 324 unique (non-redundant) sequences were identified. QRT-PCR experiments were performed for 53 transcripts using a novel experimental design that included replicate temperate populations that do undergo photoperiodic diapause and replicate tropical populations that do not undergo a photoperiodic diapause. There was greater abundance of an epithelial membrane protein transcript under short-day versus long-day photoperiods in multiple temperate, but not tropical, populations. This gene may function during the diapause program by increasing desiccation resistance or energy reserves. The expression of a phosphatidylethanolamine-binding protein transcript in response to SD versus LD photoperiod differed between temperate and tropical populations but does not appear to be causally involved in diapause. Rapid Amplification of cDNA Ends (RACE) was performed to determine the entire cDNA sequence of both transcripts.

The "switching on" of mammalian spermatozoa: molecular events involved in promotion and regulation of capacitation

Following the discovery of mammalian sperm capacitation and its fundamental importance for the acquisition of fertilizing potential, it has gradually become possible to identify some specific molecules and molecular events that play pivotal roles in the "switching on" of spermatozoa. These are discussed in the context of the promotion and regulation of capacitation, emphasizing differences between commonly used conditions in vitro and the environment in vivo where spermatozoa normally undergo capacitation. Although typical culture media used in vitro do support capacitation, they do not prevent capacitated cells from undergoing spontaneous acrosome reactions and so losing fertilizing potential. This is not a problem in vitro, but could be in vivo where few spermatozoa reach the site of fertilization. Several small molecules, known to be present in vivo, have been shown in vitro to bind to spermatozoa and to regulate capacitation, first accelerating capacitation and then inhibiting spontaneous acrosome reactions, by regulating cAMP production. Since spermatozoa would contact these molecules during and after ejaculation, it is plausible that they serve a similar function in vivo. The mechanisms whereby the presence or absence of decapacitation factors might alter plasma membrane architecture and so alter functionality of a number of membrane-associated enzymes involved in capacitation are also considered. Finally, several unresolved issues relating to events during capacitation are discussed.

Proteomic comparison of detergent-extracted sperm proteins from bulls with different fertility indexes

Intrinsic factors such as proteins modulate the fertilising ability of male gametes. We compared detergent-extracted sperm protein composition of bulls with different fertility indexes in order to highlight putative fertility markers of sperm. Frozen semen from 23 Holstein bulls with documented fertility was used. According to their ‘fertility solution’ (SOL), as calculated by the Canadian dairy network, bulls were divided into four groups: high fertility (HF) (SOL>3.0; n=6), medium-HF (2.9>SOL>2.0; n=5), medium-low fertility (−2.8>SOL>−4.9; n=8) and low fertility (LF; SOL<−5.0; n=4), with a SOL=0 being the average. Triton X-100 protein extracts from ejaculated spermatozoa were subjected to two-dimensional difference gel electrophoresis, and polypeptide maps were quantitatively analysed by ImageMaster software. Nine protein spots showed significant differences between the HF and LF groups, and eight of these proteins were identified by liquid chromatography–tandem mass spectrometry. T-complex protein 1 subunits ε and θ (CCT5 and CCT8), two isoforms of epididymal sperm-binding protein E12 (ELSPBP1), proteasome subunit α type-6 and binder of sperm 1 (BSP1) were more expressed in the LF group than in the HF group. On the other hand, adenylate kinase isoenzyme 1 (AK1) and phosphatidylethanolamine-binding protein 1 (PEBP1) were more expressed in the HF group than in the LF group. The presence and expression level of ELSPBP1, BSP1, AK1 and PEBP1 were confirmed by western blot. A linear regression model established that CCT5 and AK1 explained 64% (P<0.001) of the fertility scores. The reported functions of these proteins are in agreement with a putative involvement in defective sperm physiology, where lower or higher levels can jeopardise sperm ability to reach and fertilise the oocyte.

Structural remodeling of GPI anchors during biosynthesis and after attachment to proteins

Glycosylphosphatidylinositol (GPI) anchoring of proteins is a conserved post-translational modification in eukaryotes. In mammalian cells, approximately 150 proteins on the plasma membrane are attached to the cell surface by GPI anchors, which confer specific properties on proteins, such as association with membrane microdomains. The structures of lipid and glycan moieties on GPI anchors are remodeled during biosynthesis and after attachment to proteins. The remodeling processes are critical for transport and microdomain-association of GPI-anchored proteins. Here, we describe the structural remodeling of GPI anchors and genes required for the processes in mammals, yeast, and trypanosomes.

Expression and characterization of the PEBP homolog genes from Drosophila

The phosphatidylethanolamine binding proteins (PEBPs) family is evolutionarily conserved and involved in different physiological phenomena. PEBPs were found in many species from bacteria to mammals. Despite numerous studies, PEBPs' biological function and mode of action remain elusive. Based on sequence homology, seven PEBP genes were detected in the Drosophila genome. Only one of them, the odorant binding protein (OBP), has been characterized. To date nothing is known concerning the expression pattern and biological roles of the six other PEBP genes. By RT-PCR and Western blot analysis, we examined expression of the PEBPs in different tissues and embryos. The 6 PEBPs were differentially expressed. Only one, CG10298, is specific of only one tissue: the testis. Additionally, by comparing in wild type and male-sterile mutants we show that CG10298 is present only during spermatid differentiation. Furthermore, by comparing structural parameters of the six PEBP proteins with those of human PEBP-1, we have established that PEBP CG10298 is most closely related to human PEBP.

Biochemical characterization of membrane fractions in murine sperm: identification of three distinct sub-types of membrane rafts

Despite enormous interest in membrane raft micro-domains, no studies in any cell type have defined the relative compositions of the raft fractions on the basis of their major components--sterols, phospholipids, and proteins--or additional raft-associating lipids such as the ganglioside, G(M1). Our previous localization data in live sperm showed that the plasma membrane overlying the acrosome represents a stabilized platform enriched in G(M1) and sterols. These findings, along with the physiological requirement for sterol efflux for sperm to function, prompted us to characterize sperm membrane fractions biochemically. After confirming limitations of commonly used detergent-based approaches, we utilized a non-detergent-based method, separating membrane fractions that were reproducibly distinct based on sterol, G(M1), phospholipid, and protein compositions (both mass amounts and molar ratios). Based on fraction buoyancy and biochemical composition, we identified at least three highly reproducible sub-types of membrane raft. Electron microscopy revealed that raft fractions were free of visible contaminants and were separated by buoyancy rather than morphology. Quantitative proteomic comparisons and fluorescence localization of lipids suggested that different organelles contributed differentially to individual raft sub-types, but that multiple membrane micro-domain sub-types could exist within individual domains. This has important implications for scaffolding functions broadly associated with rafts. Most importantly, we show that the common practice of characterizing membrane domains as either "raft" or "non-raft" oversimplifies the actual biochemical complexity of cellular membranes.

The CAP superfamily: cysteine-rich secretory proteins, antigen 5, and pathogenesis-related 1 proteins--roles in reproduction, cancer, and immune defense

The cysteine-rich secretory proteins, antigen 5, and pathogenesis-related 1 proteins (CAP) superfamily members are found in a remarkable range of organisms spanning each of the animal kingdoms. Within humans and mice, there are 31 and 33 individual family members, respectively, and although many are poorly characterized, the majority show a notable expression bias to the reproductive tract and immune tissues or are deregulated in cancers. CAP superfamily proteins are most often secreted and have an extracellular endocrine or paracrine function and are involved in processes including the regulation of extracellular matrix and branching morphogenesis, potentially as either proteases or protease inhibitors; in ion channel regulation in fertility; as tumor suppressor or prooncogenic genes in tissues including the prostate; and in cell-cell adhesion during fertilization. This review describes mammalian CAP superfamily gene expression profiles, phylogenetic relationships, protein structural properties, and biological functions, and it draws into focus their potential role in health and disease. The nine subfamilies of the mammalian CAP superfamily include: the human glioma pathogenesis-related 1 (GLIPR1), Golgi associated pathogenesis related-1 (GAPR1) proteins, peptidase inhibitor 15 (PI15), peptidase inhibitor 16 (PI16), cysteine-rich secretory proteins (CRISPs), CRISP LCCL domain containing 1 (CRISPLD1), CRISP LCCL domain containing 2 (CRISPLD2), mannose receptor like and the R3H domain containing like proteins. We conclude that overall protein structural conservation within the CAP superfamily results in fundamentally similar functions for the CAP domain in all members, yet the diversity outside of this core region dramatically alters target specificity and, therefore, the biological consequences.

Beta-defensin 22 is a major component of the mouse sperm glycocalyx

Surface components of sperm isolated from the cauda epididymides were stabilized by whole sperm fixation for immunization of rabbits. The resulting immunoglobulins (Igs) recognized a single protein of 130 kDa (non-reduced) or 54-57 kDa (reduced) on western blots of cauda sperm. Igs recognized the same 54-57 kDa protein band on whole tissue blots of the corpus and cauda epididymidis and vas deferens. No immunoreactive bands were detected on blots of the prostate, seminal vesicles, testes, caput epididymis, or any of various non-reproductive tissues. Removal of sperm from the vas deferens prior to blotting eliminated the detection of the sperm antigen. Antibodies raised to synthetic peptides, identical in amino acid sequence to two unique spans of DEFB22, recognized the same 130/54-57 kDa antigen on western blots of both caudal sperm and the purified antigen isolated with the anti-sperm Ig. From indirect immunofluorescence, both the anti-sperm and anti-peptide Igs appeared to localize to the entire sperm surface, a pattern confirmed at the ultrastructural level. Real-time PCR identified the corpus epididymides as the major site of expression of DEFB22, with negligible expression in the testes, caput epididymides, and vas deferens. Immunostaining of epididymal sections showed DEFB22 being released into the lumen at the distal caput/proximal corpus, with sperm becoming intensely coated with DEFB22 as they reached the distal corpus. Most uterine sperm recovered from mice 4 h following copulation exhibited DEFB22 coating the entire sperm surface. By contrast, some sperm recovered from the oviduct and cumulus extracellular matrix showed loss of DEFB22 from the sperm head.

Association of the protein D and protein E forms of rat CRISP1 with epididymal sperm

Cysteine-rich secretory protein 1 (CRISP1) is a secretory glycoprotein produced by the rat epididymal epithelium in two forms, referred to as proteins D and E. CRISP1 has been implicated in sperm-egg fusion and has been shown to suppress capacitation in rat sperm. Several studies have suggested that CRISP1 associates transiently with the sperm surface, whereas others have shown that at least a portion of CRISP1 persists on the surface. In the present study, we demonstrate that protein D associates transiently with the sperm surface in a concentration-dependent manner, exhibiting saturable binding to both caput and cauda sperm in a concentration range that is consistent with its capacitation-inhibiting activity. In contrast, protein E persists on the sperm surface after all exogenous protein D has been dissociated. Comparison of caput and cauda sperm reveal that protein E becomes bound to the sperm in the cauda epididymidis. We show that protein E associates with caput sperm, which do not normally have it on their surfaces, in vitro in a time- and temperature-dependent manner. These studies demonstrate that most CRISP1 interacts with sperm transiently, possibly with a specific receptor on the sperm surface, consistent with its action in suppressing capacitation during epididymal storage of sperm. These studies also confirm a tightly bound population of protein E that could act in the female tract.

Biosynthesis, remodelling and functions of mammalian GPI-anchored proteins: recent progress

More than 100 mammalian proteins are post-translationally modified by glycosylphosphatidylinositol (GPI) at their C-termini and are anchored to the cell surface membrane via the lipid portion. GPI-anchored proteins (GPI-APs) have various functions, such as hydrolytic enzymes, receptors, adhesion molecules, complement regulatory proteins and other immunologically important proteins. GPI-anchored proteins are mainly associated with membrane microdomains or membrane rafts enriched in sphingolipids and cholesterol. It is thought that association with membrane rafts is important for GPI-APs in signal transduction and other functions. Here, we review recent progress in studies on biosynthesis, remodelling and functions of mammalian GPI-APs.

Signaling crossroads: the function of Raf kinase inhibitory protein in cancer, the central nervous system and reproduction

The Raf kinase inhibitory protein 1 (RKIP-1) and its orthologs are conserved throughout evolution and widely expressed in eukaryotic organisms. In its non-phosphorylated form RKIP-1 negatively regulates the Raf/MEK/ERK pathway by interfering with the activity of Raf-1. In its phosphorylated state, RKIP-1 dissociates from Raf-1 and inhibits GRK-2, a negative regulator of G-protein coupled receptors (GPCRs). Available data indicate that the phosphorylation of RKIP-1 by PKC can stimulate both the Raf/MEK/ERK and GPCR pathways. RKIP-1 has also been implicated as a negative regulator of the NF-kappaB pathway. Recent studies have shown that phosphorylated RKIP-1 binds to the centrosomal and kinetochore regions of metaphase chromosomes, where it may be involved in regulating the partitioning of chromosomes and the progression through mitosis. The collective evidence indicates that RKIP-1 regulates the activity and mediates the crosstalk between several important cellular signaling pathways. A variety of ablative interventions suggest that reduced RKIP-1 function may influence metastasis, angiogenesis, resistance to apoptosis, and genome integrity. Attenuation of RKIP-1 may also affect cardiac and neurological functions, spermatogenesis, sperm decapacitation, and reproductive behavior. In this review, the role of RKIP-1 in cellular signaling, and especially its functions revealed using a mouse knockout model, are discussed.