Identification and characterization of cystatin-related epididymal spermatogenic protein in human spermatozoa: localization in the equatorial segment

Host defense amyloids: Biosensors of the immune system?

There is considerable evidence showing that highly ordered aggregate structures known as amyloids carry out essential biological roles in species ranging from bacteria to humans. Indeed, many antimicrobial peptides/proteins form amyloids to carry out their host defense functions and many amyloids are antimicrobial. The similarity of host defense amyloids from bacterial biofilms to the mammalian epididymal amyloid matrix implies highly conserved host defense structures/functions. With an emphasis on the epididymal amyloid matrix, here we review the common properties of host defense amyloids including unique traits that would allow them to function as powerful biosensors of the immune system.

Host defense functions of the epididymal amyloid matrix

The epididymal lumen is an immunologically distinct environment. It maintains tolerance for the naturally antigenic spermatozoa to allow their maturation into functional cells while simultaneously defending against pathogens that can ascend the male tract and cause infertility. We previously demonstrated that a nonpathological amyloid matrix that includes several cystatin-related epididymal spermatogenic (CRES) subgroup family members is distributed throughout the mouse epididymal lumen but its function was unknown. Here, we reveal a role for the epididymal amyloid matrix in host defense and demonstrate that the CRES amyloids and CD-1 mouse epididymal amyloid matrix exhibit potent antimicrobial activity against bacterial strains that commonly cause epididymal infections in men. We show the CRES and epididymal amyloids use several defense mechanisms including bacterial trapping, disruption of bacterial membranes and promotion of unique bacterial ghost-like structures. Remarkably, these antimicrobial actions varied depending on the bacterial strain indicating CRES amyloids and the epididymal amyloids elicit strain-specific host defense responses. We also demonstrate that the CRES monomer and immature assemblies of the epididymal amyloid transitioned into advanced structures in the presence of bacteria, suggesting their amyloid-forming/shape-shifting properties allows for a rapid reaction to a pathogen and provides an inherent plasticity in their host defense response. Together, our studies reveal new mechanistic insight into how the male reproductive tract defends against pathogens. Future studies using a mouse model for human epididymitis are needed to establish the epididymal amyloid responses to pathogens in vivo. Broadly, our studies provide an example of why nature has maintained the amyloid fold throughout evolution.

Functional Mammalian Amyloids and Amyloid-Like Proteins

Amyloids are highly ordered fibrous cross-β protein aggregates that are notorious primarily because of association with a variety of incurable human and animal diseases (termed amyloidoses), including Alzheimer’s disease (AD), Parkinson’s disease (PD), type 2 diabetes (T2D), and prion diseases. Some amyloid-associated diseases, in particular T2D and AD, are widespread and affect hundreds of millions of people all over the world. However, recently it has become evident that many amyloids, termed “functional amyloids,” are involved in various activities that are beneficial to organisms. Functional amyloids were discovered in diverse taxa, ranging from bacteria to mammals. These amyloids are involved in vital biological functions such as long-term memory, storage of peptide hormones and scaffolding melanin polymerization in animals, substrate attachment, and biofilm formation in bacteria and fungi, etc. Thus, amyloids undoubtedly are playing important roles in biological and pathological processes. This review is focused on functional amyloids in mammals and summarizes approaches used for identifying new potentially amyloidogenic proteins and domains.

A novel zebrafish model to emulate lung injury by folate deficiency-induced swim bladder defectiveness and protease/antiprotease expression imbalance

Lung injury is one of the pathological hallmarks of most respiratory tract diseases including asthma, acute respiratory distress syndrome (ARDS) and chronic obstructive pulmonary disease (COPD). It involves progressive pulmonary tissue damages which are usually irreversible and incurable. Therefore, strategies to facilitate drug development against lung injury are needed. Here, we characterized the zebrafish folate-deficiency (FD) transgenic line that lacks a fully-developed swim bladder. Whole-mount in-situ hybridization revealed comparable distribution patterns of swim bladder tissue markers between wild-type and FD larvae, suggesting a proper development of swim bladder in early embryonic stages. Unexpectedly, neutrophils infiltration was not observed in the defective swim bladder. Microarray analysis revealed a significant increase and decrease of the transcripts for cathepsin L and a cystatin B (CSTB)-like (zCSTB-like) proteins, respectively, in FD larvae. The distribution of cathepsin L and the zCSTB-like transcripts was spatio-temporally specific in developing wild-type embryos and, in appropriate measure, correlated with their potential roles in maintaining swim bladder integrity. Supplementing with 5-formyltetrahydrofolate successfully prevented the swim bladder anomaly and the imbalanced expression of cathepsin L and the zCSTB-like protein induced by folate deficiency. Injecting the purified recombinant zebrafish zCSTB-like protein alleviated FD-induced swim bladder anomaly. We concluded that the imbalanced expression of cathepsin L and the zCSTB-like protein contributed to the swim bladder malformation induced by FD and suggested the potential application of this transgenic line to model the lung injury and ECM remodeling associated with protease/protease inhibitor imbalance.

The epididymal amyloid matrix: structure and putative functions

BACKGROUND

We previously demonstrated the normal mouse epididymal lumen contains a non-pathological amyloid matrix that surrounds spermatozoa and plays important roles in sperm maturation and protection.

OBJECTIVE

The objective herein was to present a review of this work, including studies showing the amyloid structures of four members of the CRES (cystatin-related epididymal spermatogenic) subgroup are integral and essential components of the amyloid matrix.

METHODS

We used conformation-dependent reagents that recognize the cross-β-sheet structure characteristic of amyloid, including thioflavin S (ThS), thioflavin T (ThT), anti-amyloid antibodies, and X-ray diffraction, as well as negative-stain transmission electron microscopy (TEM) to visualize amyloid structures in the epididymal lumen. Antibodies that specifically detect each CRES subgroup family member were also used in indirect immunofluorescence analysis.

RESULTS AND DISCUSSION

The epididymal lumen contains an amyloid matrix that surrounds maturing spermatozoa and represents a functional amyloid. Alterations in the structure of the amyloid matrix by the loss of the CRES subgroup members or the overexpression of cystatin C result in epididymal pathologies, including infertility. Preliminary data suggest the epididymal amyloid matrix is structurally and functionally similar to bacterial biofilms.

CONCLUSION

Together, these results suggest the amyloid matrix serves important roles in epididymal function including sperm maturation and protection.

Expression analysis of a panel of cancer-testis antigens in bladder cancer

AIM

Cancer-testis antigens (CTAs) have specific expression in gametogenic tissues and aberrant expression in cancers. Materials & methods: We assessed expression of five testis-specific genes namely KIF2B, CST8, TMEM225, RBM46, OAZ3 in bladder cancer tissues, adjacent non-neoplastic tissues and urinary cell pellets (UCPs) of bladder cancer patients compared with nonmalignant conditions.

RESULTS

Expressions of all CTAs were higher in UCPs of bladder cancer patients compared with nonmalignant conditions. RBM46 expression in UCPs was higher in patients with recurrent tumors compared with primary tumors and in patients without hematuria compared with those having hematuria. TMEM225 expression in tumoral tissues was higher in high-grade tumors compared with low-grade tumors.

CONCLUSION

Expression analysis of CTAs in UCP might provide diagnostic information about bladder cancer.

Functional Amyloids in Reproduction

Amyloids are traditionally considered pathological protein aggregates that play causative roles in neurodegenerative disease, diabetes and prionopathies. However, increasing evidence indicates that in many biological systems nonpathological amyloids are formed for functional purposes. In this review, we will specifically describe amyloids that carry out biological roles in sexual reproduction including the processes of gametogenesis, germline specification, sperm maturation and fertilization. Several of these functional amyloids are evolutionarily conserved across several taxa, including human, emphasizing the critical role amyloids perform in reproduction. Evidence will also be presented suggesting that, if altered, some functional amyloids may become pathological.

Cystatin-related epididymal spermatogenic subgroup members are part of an amyloid matrix and associated with extracellular vesicles in the mouse epididymal lumen

STUDY QUESTION

Do the CRES (cystatin-related epididymal spermatogenic) subgroup members, including CRES2, CRES3 and cystatin E2, contribute to the formation of a nonpathological, functional amyloid matrix in the mouse epididymal lumen?

SUMMARY ANSWER

CRES2, CRES3 and cystatin E2 self-assemble with different aggregation properties into amyloids in vitro, are part of a common amyloid matrix in the mouse epididymal lumen and are present in extracellular vesicles.

WHAT IS KNOWN ALREADY

Although previously thought only to be pathological, accumulating evidence has established that amyloids, which are highly ordered protein aggregates, can also carry out functional roles in the absence of pathology. We previously demonstrated that nonpathological amyloids are present in the epididymis; specifically, that the reproductive cystatin CRES forms amyloid and is present in the mouse epididymal lumen in a film-like amyloid matrix that is intimately associated with spermatozoa. Because the related proteins CRES2, CRES3 and cystatin E2 are also expressed in the epididymis, the present studies were carried out to determine if these proteins are also amyloidogenic in vitro and in vivo and thus may coordinately function with CRES as an amyloid structure.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

The epididymides from CD1 and Cst8 (CRES)129SvEv/B6 gene knockout (KO) and wild-type mice and antibodies that specifically recognize each CRES subgroup member were used for immunohistochemical and biochemical analyzes of CRES subgroup proteins. Methods classically used to identify amyloid, including the conformation-dependent dyes thioflavin S (ThS) and thioflavin T (ThT), conformation-dependent antibodies, protein aggregation disease ligand (which binds any amyloid independent of sequence) and negative stain electron microscopy (EM) were carried out to examine the amyloidogenic properties of CRES subgroup members. Immunofluorescence analysis and confocal microscopy were used for colocalization studies.

MAIN RESULTS AND THE ROLE OF CHANCE

Immunoblot and immunofluorescence analyzes showed that CRES2, CRES3 and cystatin E2 were primarily found in the initial segment and intermediate zone of the epididymis and were profoundly downregulated in epididymides from CRES KO mice, suggesting integrated functions. Except for CRES3, which was only detected in a particulate form, proteins were present in the epididymal lumen in both soluble and particulate forms including in a film-like matrix and in extracellular vesicles. The use of amyloid-specific reagents determined that all CRES subgroup members were present as amyloids and colocalized to a common amyloid matrix present in the epididymal lumen. Negative stain EM, dot blot analysis and ThT plate assays showed that recombinant CRES2, CRES3 and cystatin E2 formed amyloid in vitro, albeit with different aggregation properties. Together, our studies demonstrate that a unique amyloid matrix composed of the CRES family of reproductive-specific cystatins and cystatin C is a normal component of the mouse epididymal lumen and may play a functional role in sperm maturation by coordinating interactions between the luminal fluid and spermatozoa.

LIMITATIONS, REASONS FOR CAUTION

The structures examined in our studies were isolated from luminal fluid obtained by puncture of the epididymis and therefore we cannot rule out some contamination by epithelial cells. Although our studies show CRES family members are associated with extracellular vesicles, we have yet to determine if proteins are present on the surface or are within the vesicles. We also have not established if narrow/apical cells are the source of the CRES family extracellular vesicles. CRES and CRES2 have been previously found in the human epididymis and associated with spermatozoa; however, we have yet to determine if the human CRES subgroup proteins are amyloidogenic and if an amyloid matrix is present in the human epididymal lumen.

WIDER IMPLICATIONS OF THE FINDINGS

Understanding the regulation and biological roles of amyloids, such as the CRES subgroup amyloid matrix that functions without causing pathology, could have broad implications for understanding pathological amyloids including those associated with neurodegenerative diseases and prionopathies.

LARGE SCALE DATA

None.

STUDY FUNDING AND COMPETING INTERESTS

This work was supported by NIH grants RO1HD033903 and RO1HD056182 to G.A.C. The authors declare there are no conflicts of interest.

Oxygen free radicals and mitochondrial signaling in oligospermia and asthenospermia

The aim of this study was to investigate the roles of oxygen free radicals and mitochondrial signaling in semen disorders, in particular, how this induces low concentrations and reduced motility of sperm. Ejaculate samples were obtained from 120 young adult males (mean age, 28.7±5.3 years) with normal semen (n=30), oligospermia (n=30), asthenospermia (n=30) and oligoasthenozoospermia (n=30). The malondialdehyde (MDA) content, total superoxide dismutase (T‑SOD) activity and glutathione peroxidase (GSH‑Px) activity of the sperm samples were determined by enzymatic assays. Mitochondrial membrane potential (MMP) was determined by flow cytometric detection of accumulated membrane‑permeable JC‑1 fluorescent dye. The mRNA and protein expression levels of apoptosis-associated genes [Bcl‑2, Bax, cytochrome c (Cyt C) and caspase-3] were measured by quantitative polymerase chain reaction and western blotting. Intergroup differences were evaluated by Student's t‑test. The sperm samples from all semen disorder groups exhibited significantly lower T‑SOD content and GSH‑Px activity (all P<0.05 versus normal sperm), and the extent of reduction revealed a disorder-associated trend (asthenospermia < oligospermia ≈ oligoasthenozoospermia). By contrast, the semen disorder groups had significantly higher MDA content (all P<0.05 versus normal sperm); the extent of this increase also revealed a disorder-associated trend (asthenospermia > oligospermia ≈ oligoasthenozoospermia). The sperm from patients with semen disorders also exhibited significantly lower MMP than normal sperm, as evidenced by lower mean ratios of JC‑1+ sperm per group. The semen disorder groups had significantly higher Bax, Cyt C and caspase-3 mRNA and protein expression levels in the sperm samples, but significantly lower levels of Bcl‑2 (all P<0.05 versus normal sperm). However, only the extent of increases in Cyt C and caspase-3 exhibited a disorder-associated trend (oligospermia > asthenospermia). In conclusion, oxygen free radicals may be involved in reduced sperm concentration and motility, possibly through effects on the mitochondrial apoptotic signaling pathway. Perturbed mitochondrial release of Cyt C may be the distinguishing molecular feature between oligospermia and asthenospermia.

Albumin is synthesized in epididymis and aggregates in a high molecular mass glycoprotein complex involved in sperm-egg fertilization

The epididymis has an important role in the maturation of sperm for fertilization, but little is known about the epididymal molecules involved in sperm modifications during this process. We have previously described the expression pattern for an antigen in epididymal epithelial cells that reacts with the monoclonal antibody (mAb) TRA 54. Immunohistochemical and immunoblotting analyses suggest that the epitope of the epididymal antigen probably involves a sugar moiety that is released into the epididymal lumen in an androgen-dependent manner and subsequently binds to luminal sperm. Using column chromatography, SDS-PAGE with insitu digestion and mass spectrometry, we have identified the protein recognized by mAb TRA 54 in mouse epididymal epithelial cells. The ∼65 kDa protein is part of a high molecular mass complex (∼260 kDa) that is also present in the sperm acrosomal vesicle and is completely released after the acrosomal reaction. The amino acid sequence of the protein corresponded to that of albumin. Immunoprecipitates with anti-albumin antibody contained the antigen recognized by mAb TRA 54, indicating that the epididymal molecule recognized by mAb TRA 54 is albumin. RT-PCR detected albumin mRNA in the epididymis and fertilization assays invitro showed that the glycoprotein complex containing albumin was involved in the ability of sperm to recognize and penetrate the egg zona pellucida. Together, these results indicate that epididymal-derived albumin participates in the formation of a high molecular mass glycoprotein complex that has an important role in egg fertilization.

Biotechnological approaches to the treatment of aspermatogenic men

Aspermatogenesis is a severe impairment of spermatogenesis in which germ cells are completely lacking or present in an immature form, which results in sterility in approximately 25% of patients. Because assisted reproduction techniques require mature germ cells, biotechnology is a valuable tool for rescuing fertility while maintaining biological fatherhood. However, this process involves, for instance, the differentiation of preexisting immature germ cells or the production/derivation of sperm from somatic cells. This review critically addresses four potential techniques: sperm derivation in vitro, germ stem cell transplantation, xenologous systems, and haploidization. Sperm derivation in vitro is already feasible in fish and mammals through organ culture or 3D systems, and it is very useful in conditions of germ cell arrest or in type II Sertoli-cell-only syndrome. Patients afflicted by type I Sertoli-cell-only syndrome could also benefit from gamete derivation from induced pluripotent stem cells of somatic origin, and human haploid-like cells have already been obtained by using this novel methodology. In the absence of alternative strategies to generate sperm in vitro, in germ cells transplantation fertility is restored by placing donor cells in the recipient germ-cell-free seminiferous epithelium, which has proven effective in conditions of spermatogonial arrest. Grafting also provides an approach for ex-vivo generation of mature sperm, particularly using prepubertal testis tissue. Although less feasible, haploidization is an option for creating gametes based on biological cloning technology. In conclusion, the aforementioned promising techniques remain largely experimental and still require extensive research, which should address, among other concerns, ethical and biosafety issues, such as gamete epigenetic status, ploidy, and chromatin integrity.

Alterations in the testis and epididymis associated with loss of function of the cystatin-related epididymal spermatogenic (CRES) protein

Cystatin-related epididymal spermatogenic protein (CRES) or cystatin 8 (Cst8 gene) is a member of the cystatin superfamily of cysteine protease inhibitors. It differs from typical cystatins because it lacks consensus sites for cysteine protease inhibition and exhibits reproductive-specific expression. In the present study, we examined CRES expression within the testes, efferent ducts, and epididymides of normal mice by light microscope immunolocalization. Alterations to these tissues in male mice lacking the Cst8 gene (Cst8(-/-2)) were also characterized by histomorphometry and electron microscopy. In the normal testis, CRES was localized exclusively in mid and late elongating spermatids. In the efferent ducts, CRES was localized to the apical region of the epithelial cells suggestive of localization in the endosomes. In the initial segment of the epididymis, principal cells showed supranuclear and luminal reactions. In the cauda region, CRES was present exclusively as aggregates in the lumen and was detected in clear cells. Compared with wild-type mice (Cst8(+/+)), older (10-12 months) Cst8(-/-) mice had modest but statistically significant reductions in tubular, epithelial, and/or luminal profile areas in the testis and epididymis. By electron microscopy, some Cst8(-/-) tubules in the testis were normal in appearance, but others showed a vacuolated seminiferous epithelium, degenerating germ cells, and alterations to ectoplasmic specializations. In the epididymal lumen, abnormally shaped sperm heads and tails were noted along with immature germ cells. In addition, principal cells contained numerous large irregularly shaped lysosomes suggestive of disrupted lysosomal functions. In both the testis and epididymis, however, these abnormalities were not apparent in younger mice (4 months), only in the older (10-12 months) Cst8(-/-) mice. These findings suggest that the altered testicular and epididymal histology reflects a cumulative effect of the loss of CRES and support a role for CRES in maintaining the normal integrity and function of the testis and epididymis.

A novel terminal ampullae peptide is involved in the proteolytic activity of sperm in the prawn, Macrobrachium rosenbergii

As the distal part of the crustacean male reproductive tract, terminal ampullae play important roles in sperm development and storage of mature spermatophores. In the present study, the novel gene terminal ampullae peptide (TAP) was cloned from terminal ampullae of the prawn, Macrobrachium rosenbergii. The cDNA sequence consists of 768 nucleotides, with an open-reading frame of 264 nucleotides which encodes a putative 88-amino acid precursor protein with a 17-amino acid residue signal peptide. Western blotting and immunohistochemical analysis revealed that TAP was distributed on terminal ampullae and sperm, and its expression was related to gonad development. To elucidate the functional role of TAP in vivo, we disrupted the TAP gene by RNA interference (RNAi) and evaluated the effect on fertility and several sperm parameters. Although there was no difference in fertility between RNAi-induced prawns and controls, RNAi treatment decreased the sperm gelatinolytic activity and blocked proteolytic activity on the vitelline coat. These data provide evidence that TAP participates in regulating sperm proteolytic activity, and performs a crucial role in sperm maturation and degradation of the vitelline coat during fertilization.

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

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

The reproductive tissue specific cystatin subgroup of genes: expression during gonadal development in wildtype and testatin knockout animals

Testatin has been implicated in fetal testis development due to its restricted expression in pre-Sertoli cells immediately after the onset of Sry gene expression. However, testatin knockout mice showed normal testis development and fertility. We investigated the spatial and temporal expression pattern of the Cres/testatin subgroup of genes, including the novel gene Cstl1/Cres4, in fetal mouse gonads and in adult testis, epididymis and ovary. The genes are related to the family 2 cystatins of protease inhibitors. Using real-time PCR and in situ hybridization we could show that 4 subgroup genes, testatin, CstSC, CstTE-1/Cres3 and Cres are expressed in fetal testis. We also confirmed the expression of testatin, CstE2, CstSC, CstTE-1/Cres3, Cres, CstT and Cstl1/Cres4 in adult testis and CstE2, CstTE-1/Cres3, Cres and CstE1/Cres2 in adult epididymis. In testatin knockout animals, the expression of CstE2 was heavily downregulated in adult testis, but not in adult epididymis, compared to wildtype controls. In conclusion, an explanation for the lack of phenotype in testatin knockout mice could be functional redundancy with another member of the Cres/testatin subgroup. The most likely candidate/s would be CstSC, CstTE-1/Cres3 or Cres as they are expressed in the fetal testicular tubules in early testis differentiation together with testatin.

Presence and subcellular localizations of surfactant proteins A and D in human spermatozoa

OBJECTIVE

To investigate the presence of surfactant protein-A (SP-A); molecular weight 34 kDa and surfactant protein-D (SP-D); and molecular weight 43 kDa in human spermatozoa.

DESIGN

Prospective, research study.

SETTING

Two universities in Turkey.

PATIENT(S)

Semen specimens (n = 10) were obtained from normozoospermic donors.

INTERVENTION(S)

Human sperm were exposed to an anti-human SP-A polyclonal antibody, and monoclonal antibody, to human SP-D protein.

MAIN OUTCOME MEASURE(S)

Presence of SP-A and SP-D proteins in human beings.

RESULT(S)

Indirect immunofluorescence assays of human sperm indicated the presence of SP-A in the mid piece, the tail, and sometimes at the equatorial region of spermatozoa. A brilliant green light detected SP-D in the tails and acrosome of some sperm. The anti-SP-A antibody detected a single band corresponding to the molecular weight values of 34 kDa in spermatozoa, whereas no band was observed in the negative control. The anti-SP-D antibody showed the expected band at 43 kDa in spermatozoa.

CONCLUSION(S)

This is the first report and a novel finding of the presence of surfactant glycoproteins on human spermatozoa.

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

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

Genome-wide profiling of segmental-regulated transcriptomes in human epididymis using oligo microarray

Sperm maturation during passage through the epididymis depends on regionalized gene expression which maintains the progressively changing environment within the epididymal tubule. Towards defining the genes that drive the sequential maturation of spermatozoa, we profiled regionally regulated gene expression pattern in the epididymis of a fertile young male donor using Affymetrix human genome U133 plus 2.0 microarray representing approximately the whole human genome. Over 15000 transcripts, almost one-third of the total on the array were identified in whole epididymis. Among them, 65% were detected in all three regions of the epididymis, 410 or 2.6% were present only in one region and the remaining 32.4% were distributed in two regions. Region-specific transcripts observed in caput (264), corpus (61) and cauda (81) epididymides were further classified as empirically determined reported genes or ESTs. This study revealed for the first time, the expression in human epididymis of a number of region-specific genes. The original data will be made publicly available on the Shanghai Science and Technology Database (http://www.scbit.org/human_epididymis_transcriptomes).

Immunolocalization and Regulation of Cystatin 12 in Mouse Testis and Epididymis1

In previous studies, we identified a new member of the male reproductive tract subgroup within family 2 cystatins, termed cystatin 12 (Cst12, previously known as Cst TE-1 or Cres3). The mouse Cst12 mRNA was primarily localized to the Sertoli cells in the testis and to the epithelial cells of the proximal caput region of the epididymis. In this report, studies were carried out to characterize the cystatin 12 (CST12) protein in mouse testis and epididymis. A recombinant His-CST12 fusion protein was expressed in E. coli and purified to generate an anti-CST12 polyclonal antibody. Western blot analysis showed little or no cross-reaction between the anti-CST12 antibody and several other known male reproductive tract cystatins. Immunohistochemistry revealed that CST12 protein was predominantly localized to the cytoplasm of Sertoli cells in the seminiferous epithelium in a stage-dependent manner. All stages showed high levels of expression except stages VII and VIII, in which very limited expression of CST12 was observed. In the epididymis, CST12 was highly expressed in the cytoplasm of the epithelial cells in the proximal caput and secreted into the lumen. The mouse CST12 protein was also detected in other regions of the epididymis; however, the localization varied greatly along the epididymal tubules. Indirect immunofluorescence showed that CST12 protein was localized to the cytoplasmic droplets in both testicular and epididymal spermatozoa. These observations suggest that CST12 protein may play a specialized role during spermatogenesis and sperm maturation. Northern blot analyses demonstrated that Cst12 transcript levels in the epididymis decreased after castration, and testosterone propionate (T) treatment further repressed the expression of this gene. However, 17-beta estradiol (E) administration maintained the expression of Cst12 mRNA after castration, whereas treatment with both T and E failed to maintain Cst12 mRNA levels in epididymis. These results suggest that androgen and estrogen, probably with other testicular factors, are involved in the regulation of this gene.

Normal sexual development and fertility in testatin knockout mice

The testatin gene was previously isolated in a screen focused on finding novel signaling molecules involved in sex determination and differentiation. testatin is specifically upregulated in pre-Sertoli cells in early fetal development, immediately after the onset of Sry expression, and was therefore considered a strong candidate for involvement in early testis development. testatin expression is maintained in the adult Sertoli cell, and it can also be found in a small population of germ cells. Testatin shows homology to family 2 cystatins, a group of broadly expressed small secretory proteins that are inhibitors of cysteine proteases in vitro but whose in vivo functions are unclear. testatin belongs to a novel subfamily among the cystatins, comprising genes that all show expression patterns that are strikingly restricted to reproductive tissue. To investigate a possible role of testatin in testis development and male reproduction, we have generated a mouse with targeted disruption of the testatin gene. We found no abnormalities in the testatin knockout mice with regard to fetal and adult testis morphology, cellular ultrastructure, body and testis weight, number of offspring, spermatogenesis, or hormonal parameters (testosterone, luteinizing hormone, and follicle-stimulating hormone).

Recapitulation of germ cell- and pituitary-specific expression with 1.6 kb of the cystatin-related epididymal spermatogenic (Cres) gene promoter in transgenic mice

The Cres (cystatin-related epididymal spermatogenic) gene encodes the defining member of a new subgroup within the family 2 cystatins of cysteine protease inhibitors. Cres expression is highly tissue- and cell-specific, with messenger RNA (mRNA) present in the testicular round/elongating spermatids, proximal caput epididymal epithelium, gonadotroph cells in the anterior pituitary gland, and corpus luteum of the ovary. To begin to elucidate the molecular mechanisms controlling the tissue- and cell-specific expression of the Cres gene, transgenic mice were generated containing 1.6 kilobases (kb) of the mouse Cres promoter linked to the bacterial chloramphenicol acetyltransferase (CAT) reporter gene. A CAT enzyme-linked immunosorbent assay detected CAT protein in the testis, epididymis, isolated cauda epididymal spermatozoa, and anterior pituitary gland from mice heterozygous and homozygous for the transgene. However, reverse transcription (RT)-PCR did not detect CAT mRNA in any regions of the epididymis, suggesting that the CAT protein detected in the epididymis was from spermatozoa. RT-PCR also did not detect CAT mRNA in the ovary. RT-PCR analysis of the testes from mice of different postnatal ages showed CAT mRNA first detected at day 22, which correlated with the first appearance of Cres mRNA and with the presence of round spermatids. These studies demonstrate that 1.6 kb of Cres promoter contains the DNA elements necessary for germ cell and pituitary gland-specific expression but lacks critical sequences necessary for expression in the epididymis and ovary.

The PATE gene is expressed in the accessory tissues of the human male genital tract and encodes a secreted sperm-associated protein

ThePATEgene is expressed in prostate and testis. To determine if PATE is expressed in other accessory tissues of the male genital tract, RT-PCR of the epididymis and seminal vesicle was performed. PATE mRNA was highly expressed in the epididymis and seminal vesicle.In situhybridization of the testis showed PATE mRNA is strongly expressed in the spermatogonia. ThePATEgene encodes a 14-kDa protein with a predicted signal sequence and a cleavage site between residues G21 and S22. To determine if PATE is a secreted protein, 293T cells were transfected with a pcDNA-PATE-myc-His plasmid and protein immunoprecipitated with anti-myc monoclonal antibody. Western blot analysis showed the presence of PATE-myc-His protein was in the medium and the cell lysate. Confocal microscopy demonstrated that PATE-myc-His protein is found in the endoplasmic reticulum. The polyclonal antibody SOL-1 was generated by immunization of rabbits with recombinant PATE protein expressed and purified fromEscherichia coli.Western blots were performed on extracts of prostate, testis, seminal vesicle and ejaculated spermatozoa, but PATE protein was only detected in the spermatozoa. Immunostaining of sperm smears revealed that PATE is located in a band-like pattern in the sperm head. Our data indicate that PATE is made by various sexual accessory tissues and secreted into the semen where it becomes associated with sperm, suggesting that PATE is a novel sperm-associated protein with a possible role in mammalian sperm maturation.

The cystatin-related epididymal spermatogenic protein inhibits the serine protease prohormone convertase 2

The cystatin-related epididymal spermatogenic (CRES) protein is related to the family 2 cystatins of the cystatin superfamily of cysteine protease inhibitors. However, CRES lacks sequences important for cysteine protease inhibitory activity and is specifically expressed in reproductive and neuroendocrine tissues. Thus, CRES is distinct from cystatins and may perform unique tissue-specific functions. The purpose of the present study was to determine whether CRES functions as a protease inhibitor in in vitro assays. In contrast to mouse recombinant cystatin C, recombinant CRES did not inhibit the cysteine proteases papain and cathepsin B, suggesting that it probably does not function as a typical cystatin. CRES, however, inhibited the serine protease prohormone convertase 2 (PC2), a protease involved in prohormone processing in the neuroendocrine system, whereas cystatin C showed no inhibition. CRES did not inhibit subtilisin, trypsin, or the convertase family members, PC1 and furin, indicating that it selectively inhibits PC2. Kinetic analysis showed that CRES is a competitive inhibitor of PC2 with a K(i) of 25 nM. The removal of N-terminal sequences from CRES decreased its affinity for PC2, suggesting that the N terminus may be important for CRES to function as an inhibitor. These studies suggest that CRES is a cross-class inhibitor that may regulate proprotein processing within the reproductive and neuroendocrine systems.

A new subgroup of the family 2 cystatins

The cystatins are a superfamily of cysteine protease inhibitors. Several genes including Cres (cystatin-related epididymal spermatogenic), testatin, and cystatin T, have been identified that are related to the family 2 cystatins but lack critical consensus sites important for cysteine protease inhibition. In addition, these genes are primarily expressed in the reproductive tract suggesting they may have evolved to perform tissue-specific functions distinct from that of the typical cystatins. This review describes the CRES subgroup within the family 2 cystatins including potential new members and their putative functions in the reproductive tract.