Biogenesis of sperm perinuclear theca and its role in sperm functional competence and fertilization

Insights into crucial molecules and protein channels involved in pig sperm cryopreservation

Cryopreservation is the most efficient procedure for long-term preservation of mammalian sperm; however, its use is not currently dominant for boar sperm before its use for artificial insemination. In fact, freezing and thawing have an extensive detrimental effect on sperm function and lead to impaired fertility. The present work summarises the basis of the structural and functional impact of cryopreservation on pig sperm that have been extensively studied in recent decades, as well as the molecular alterations in sperm that are related to this damage. The wide variety of mechanisms underlying the consequences of alterations in expression levels and structural modifications of sperm proteins with diverse functions is detailed. Moreover, the use of cryotolerance biomarkers as predictors of the potential resilience of a sperm sample to the cryopreservation process is also discussed. Regarding the proteins that have been identified to be relevant during the cryopreservation process, they are classified according to the functions they carry out in sperm, including antioxidant function, plasma membrane protection, sperm motility regulation, chromatin structure, metabolism and mitochondrial function, heat-shock response, premature capacitation and sperm-oocyte binding and fusion. Special reference is made to the relevance of sperm membrane channels, as their function is crucial for boar sperm to withstand osmotic shock during cryopreservation. Finally, potential aims for future research on cryodamage and cryotolerance are proposed, which might be crucial to minimise the side-effects of cryopreservation and to make it a more advantageous strategy for boar sperm preservation.

Deletion of ACTRT1 is associated with male infertility as sperm acrosomal ultrastructural defects and fertilization failure in human

STUDY QUESTION

Could actin-related protein T1 (ACTRT1) deficiency be a potential pathogenic factor of human male infertility?

SUMMARY ANSWER

A 110-kb microdeletion of the X chromosome, only including the ACTRT1 gene, was identified as responsible for infertility in two Chinese males with sperm showing acrosomal ultrastructural defects and fertilization failure.

WHAT IS KNOWN ALREADY

The actin-related proteins (e.g. ACTRT1, ACTRT2, ACTL7A, and ACTL9) interact with each other to form a multimeric complex in the subacrosomal region of spermatids, which is crucial for the acrosome-nucleus junction. Actrt1-knockout (KO) mice are severely subfertile owing to malformed sperm heads with detached acrosomes and partial fertilization failure. There are currently no reports on the association between ACTRT1 deletion and male infertility in humans.

STUDY DESIGN, SIZE, DURATION

We recruited a cohort of 120 infertile males with sperm head deformations at a large tertiary hospital from August 2019 to August 2023. Genomic DNA extracted from the affected individuals underwent whole exome sequencing (WES), and in silico analyses were performed to identify genetic variants. Morphological analysis, functional assays, and ART were performed in 2022 and 2023.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The ACTRT1 deficiency was identified by WES and confirmed by whole genome sequencing, PCR, and quantitative PCR. Genomic DNA of all family members was collected to define the hereditary mode. Papanicolaou staining and electronic microscopy were performed to reveal sperm morphological changes. Western blotting and immunostaining were performed to explore the pathological mechanism of ACTRT1 deficiency. ICSI combined with artificial oocyte activation (AOA) was applied for one proband.

MAIN RESULTS AND THE ROLE OF CHANCE

We identified a whole-gene deletion variant of ACTRT1 in two infertile males, which was inherited from their mothers, respectively. The probands exhibited sperm head deformations owing to acrosomal detachment, which is consistent with our previous observations on Actrt1-KO mice. Decreased expression and ectopic distribution of ACTL7A and phospholipase C zeta were observed in sperm samples from the probands. ICSI combined with AOA effectively solved the fertilization problem in Actrt1-KO mice and in one of the two probands.

LIMITATIONS, REASONS FOR CAUTION

Additional cases are needed to further confirm the genetic contribution of ACTRT1 variants to male infertility.

WIDER IMPLICATIONS OF THE FINDINGS

Our results reveal a gene-disease relation between the ACTRT1 deletion described here and human male infertility owing to acrosomal detachment and fertilization failure. This report also describes a good reproductive outcome of ART with ICSI-AOA for a proband.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Chongqing medical scientific research project (Joint project of Chongqing Health Commission and Science and Technology Bureau, 2023MSXM008 and 2023MSXM054). There are no competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

Cryopreservation of equine spermatozoa reduces plasma membrane integrity and phospholipase C zeta 1 content as associated with oocyte activation

BACKGROUND

Phospholipase C zeta (PLCZ1) is considered the major sperm-borne oocyte activation factor. Cryopreserved stallion spermatozoa are commonly used for intracytoplasmic sperm injection (ICSI). However, plasma membrane damage and protein modifications caused by cryopreservation could impair sperm structure and function, leading to a reduction of PLCZ1 and oocyte activation after ICSI.

OBJECTIVES

We compared membrane integrity and PLCZ1 abundance in populations for fresh, frozen, and refrozen stallion spermatozoa, either thawed and refrozen at room or low temperature; and examined the effect of relative PLCZ1 content on cleavage after ICSI.

MATERIALS AND METHODS

Western blotting, ELISA, and immunofluorescence were conducted in stallion spermatozoa, freezing extenders, and detergent-extracted sperm fractions to detect and quantify PLCZ1. Retrospectively, PLCZ1 content and cleavage rate were analyzed. Fresh, frozen, and refrozen at room and low temperatures spermatozoa were evaluated for acrosomal and plasma membrane integrity and PLCZ1 content using flow cytometry.

RESULTS

Western blotting, ELISA, and immunofluorescence revealed significant reduction of PLCZ1 in spermatozoa after cryopreservation and confirmed PLCZ1 detection in extenders. After detergent extraction, a PLCZ1-nonextractable fraction remained in the postacrosomal region of spermatozoa. Plasma membrane integrity was significantly reduced after freezing. Acrosomal and plasma membrane integrity were similar between frozen and refrozen samples at low temperature, but both were significantly higher than samples refrozen at room temperature. Acrosomal and plasma membrane integrity significantly correlated to PLCZ1 content. Percentages of PLCZ1-labeled spermatozoa and PLCZ1 content were reduced after freezing but not after refreezing. Relative content and localization of PLCZ1 were associated with cleavage rates after ICSI.

DISCUSSION AND CONCLUSION

Sperm PLCZ1 content associates with cleavage rates after ICSI. Cryopreservation is detrimental to sperm plasma membrane integrity and PLCZ1 retention. However, refreezing did not result in additional PLCZ1 loss. Refreezing stallion spermatozoa at a low temperature resulted in better survival but did not improve PLCZ1 retention.

Disruption in CYLC1 leads to acrosome detachment, sperm head deformity, and male in/subfertility in humans and mice

The perinuclear theca (PT) is a dense cytoplasmic web encapsulating the sperm nucleus. The physiological roles of PT in sperm biology and the clinical relevance of variants of PT proteins to male infertility are still largely unknown. We reveal that cylicin-1, a major constituent of the PT, is vital for male fertility in both mice and humans. Loss of cylicin-1 in mice leads to a high incidence of malformed sperm heads with acrosome detachment from the nucleus. Cylicin-1 interacts with itself, several other PT proteins, the inner acrosomal membrane (IAM) protein SPACA1, and the nuclear envelope (NE) protein FAM209 to form an 'IAM-cylicins-NE' sandwich structure, anchoring the acrosome to the nucleus. WES (whole exome sequencing) of more than 500 Chinese infertile men with sperm head deformities was performed and a CYLC1 variant was identified in 19 patients. Cylc1-mutant mice carrying this variant also exhibited sperm acrosome/head deformities and reduced fertility, indicating that this CYLC1 variant most likely affects human male reproduction. Furthermore, the outcomes of assisted reproduction were reported for patients harbouring the CYLC1 variant. Our findings demonstrate a critical role of cylicin-1 in the sperm acrosome-nucleus connection and suggest CYLC1 variants as potential risk factors for human male fertility.

A Possible Role for Nerve Growth Factor and Its Receptors in Human Sperm Pathology

Nerve growth factor (NGF) signalling affects spermatogenesis and mature sperm traits. In this paper, we aimed to evaluate the distribution and the role of NGF and its receptors (p75NTR and TrKA) on the reproductive apparatus (testis and epididymis) and sperm of fertile men (F) and men with different pathologies, namely varicocele (V) and urogenital infections (UGIs). We collected semen samples from 21 individuals (31-40 years old) subdivided as follows: V (n = 7), UGIs (n = 7), and F (n = 7). We submitted the semen samples to bacteriological analysis, leucocyte identification, and analysis of sperm parameters (concentration, motility, morphology, and viability). We determined the seminal plasma levels of NGF, interleukin 1β (IL-1β), and F2-isoprostanes (F2-IsoPs), and the gene and protein expression of NGF receptors on sperm. We also used immunofluorescence to examine NGF receptors on ejaculated sperm, testis, and epididymis. As expected, fertile men showed better sperm parameters as well as lower levels of NGF, F2-IsoPs, and IL-1β compared with men with infertility. Notably, in normal sperm, p75NTR and TrKA were localised throughout the entire tail. TrKA was also found in the post-acrosomal sheath. This localisation appeared different in patients with infertility: in particular, there was a strong p75NTR signal in the midpiece and the cytoplasmic residue or coiled tails of altered ejaculated sperm. In line with these findings, NGF receptors were intensely expressed in the epididymis and interstitial tissue of the testis. These data suggest the distinctive involvement of NGF and its receptors in the physiology of sperm from fertile men and men with infertility, indicating a possible role for new targeted treatment strategies.

Phospholipase C Zeta 1 (PLCZ1): The Function and Potential for Fertility Assessment and In Vitro Embryo Production in Cattle and Horses

Phospholipase C Zeta 1 (PLCZ1) is considered a major sperm-borne oocyte activation factor. After gamete fusion, PLCZ1 triggers calcium oscillations in the oocyte, resulting in oocyte activation. In assisted fertilization, oocyte activation failure is a major cause of low fertility. Most cases of oocyte activation failures in humans related to male infertility are associated with gene mutations and/or altered PLCZ1. Consequently, PLCZ1 evaluation could be an effective diagnostic marker and predictor of sperm fertilizing potential for in vivo and in vitro embryo production. The characterization of PLCZ1 has been principally investigated in men and mice, with less known about the PLCZ1 impact on assisted reproduction in other species, such as cattle and horses. In horses, sperm PLCZ1 varies among stallions, and sperm populations with high PLCZ1 are associated with cleavage after intracytoplasmic sperm injection (ICSI). In contrast, bull sperm is less able to initiate calcium oscillations and undergo nuclear remodeling, resulting in poor cleavage after ICSI. Advantageously, injections of PLCZ1 are able to rescue oocyte failure in mouse oocytes after ICSI, promoting full development and birth. However, further research is needed to optimize PLCZ1 diagnostic tests for consistent association with fertility and to determine whether PLCZ1 as an oocyte-activating treatment is a physiological, efficient, and safe method for improving assisted fertilization in cattle and horses.

Cryopreservation, in addition to protein tyrosine phosphorylation, alters the distribution of phosphatidyl inositol bisphosphate and the localization of cytoskeletal and signaling proteins (gelsolin, tyrosine kinase c-SRC and phospholipase C-ζ) in the perinuclear theca of boar sperm

Cryopreservation of boar spermatozoa affects the perinuclear theca (PT) and involves several proteins and molecules that play important roles during capacitation and the acrosomal reaction. The objective of the present study was to evaluate whether the deleterious effects of cryopreservation in addition to protein tyrosine phosphorylation are accompanied by changes in the distribution of phosphatidyl inositol bisphosphate (PIP2) and the localization of cytoskeletal and signaling proteins in the perinuclear theca of cryopreserved boar spermatozoa. For this purpose, by immunocytochemistry (IC) the changes in localization of phosphorylated proteins in tyrosine residues, gelsolin, c-SRC kinase and PLC-ζ, as well as in the distribution of phosphatidyl inositol bisphosphate were analyzed in thawed spermatozoa (T) non capacitated (NC), capacitated (C) and in those with acrosomal reaction (AR) and compared with fresh spermatozoa (F) under the same physiological status. Western blotting (WB) and co-immunoprecipitation were performed to confirm the presence of these proteins in PT and to determine the interaction between these molecules. IC showed that immunostaining for phosphorylated proteins significantly increased in the acrosomal region and flagellum in TNC spermatozoa (p < 0.05). The proportion of cells displaying immunolabeling for gelsolin in the acrosomal region decreased after capacitation in cryopreserved spermatozoa; the same change was found (p < 0.05) in the proportion of spermatozoa immunoreactive to PIP2 in the sperm head. c-SRC was observed in the equatorial segment and acrosomal region, subdomains that coincide with the site where phosphorylated proteins were detected. PLC-ζ immunolocalization in fresh spermatozoa underwent changes after capacitation and acrosomal reaction, with a significant increase in the equatorial segment and post-acrosomal region in cryopreserved spermatozoa (p < 0.05). WB analysis indicated the presence of gelsolin, c-SRC and PLC-ζ in PT; besides, we confirmed that gelsolin co-immunoprecipitated with c-SRC and PLC-ζ, which changes according to the physiological state of spermatozoa. As a conclusion, cryopreservation together with increased immunodetection of tyrosine phosphorylated proteins decreases the detection of PIP2 and alters the immunolocalization patterns of gelsolin, c-SRC and PLC-ζ in the PT in boar spermatozoa.

Cylicins are a structural component of the sperm calyx being indispensable for male fertility in mice and human

Cylicins are testis-specific proteins, which are exclusively expressed during spermiogenesis. In mice and humans, two Cylicins, the gonosomal X-linked Cylicin 1 (Cylc1/CYLC1) and the autosomal Cylicin 2 (Cylc2/CYLC2) genes, have been identified. Cylicins are cytoskeletal proteins with an overall positive charge due to lysine-rich repeats. While Cylicins have been localized in the acrosomal region of round spermatids, they resemble a major component of the calyx within the perinuclear theca at the posterior part of mature sperm nuclei. However, the role of Cylicins during spermiogenesis has not yet been investigated. Here, we applied CRISPR/Cas9-mediated gene editing in zygotes to establish Cylc1- and Cylc2-deficient mouse lines as a model to study the function of these proteins. Cylc1 deficiency resulted in male subfertility, whereas Cylc2-/-, Cylc1-/yCylc2+/-, and Cylc1-/yCylc2-/- males were infertile. Phenotypical characterization revealed that loss of Cylicins prevents proper calyx assembly during spermiogenesis. This results in decreased epididymal sperm counts, impaired shedding of excess cytoplasm, and severe structural malformations, ultimately resulting in impaired sperm motility. Furthermore, exome sequencing identified an infertile man with a hemizygous variant in CYLC1 and a heterozygous variant in CYLC2, displaying morphological abnormalities of the sperm including the absence of the acrosome. Thus, our study highlights the relevance and importance of Cylicins for spermiogenic remodeling and male fertility in human and mouse, and provides the basis for further studies on unraveling the complex molecular interactions between perinuclear theca proteins required during spermiogenesis.

Lysophosphatidic Acid Signalling Regulates Human Sperm Viability via the Phosphoinositide 3-Kinase/AKT Pathway

Lysophosphatidic acid (LPA) signalling is essential for maintaining germ cell viability during mouse spermatogenesis; however, its role in human spermatozoa is unknown. We previously demonstrated that peroxiredoxin 6 (PRDX6) calcium-independent phospholipase A2 (iPLA2) releases lysophospholipids such as LPA or arachidonic acid (AA) and that inhibiting PRDX6 iPLA2 activity impairs sperm cell viability. The exogenous addition of LPA bypassed the inhibition of PRDX6 iPLA2 activity and maintained the active phosphoinositide 3-kinase (PI3K)/AKT pathway. Here, we aimed to study PI3K/AKT pathway regulation via LPA signalling and protein kinases in maintaining sperm viability. The localization of LPARs in human spermatozoa was determined using immunocytochemistry, and P-PI3K and P-AKT substrate phosphorylations via immunoblotting. Sperm viability was determined using the hypo-osmotic swelling test. LPAR1, 3, 5 and 6 were located on the sperm plasma membrane. The inhibition of LPAR1-3 with Ki16425 promoted the impairment of sperm viability and decreased the phosphorylation of PI3K AKT substrates. Inhibitors of PKC, receptor-type PTK and PLC impaired sperm viability and the PI3K/AKT pathway. Adding 1-oleoyl-2-acetyl-snglycerol (OAG), a cell-permeable analog of diacylglycerol (DAG), prevented the loss of sperm viability and maintained the phosphorylation of PI3K. In conclusion, human sperm viability is supported by LPAR signalling and regulated by PLC, PKC and RT-PTK by maintaining phosphorylation levels of PI3K and AKT substrates.

Human Sperm Head Vacuoles Are Related to Nuclear-Envelope Invaginations

Nuclear vacuoles are specific structures present on the head of the human sperm of fertile and non-fertile men. Human sperm head vacuoles have been previously studied using motile sperm organelle morphology examination (MSOME) and their origin related to abnormal morphology, abnormal chromatin condensation and DNA fragmentation. However, other studies argued that human sperm vacuoles are physiological structures and consequently, to date, the nature and origin of the nuclear vacuoles remains to be elucidated. Here, we aim to define the incidence, position, morphology and molecular content of the human sperm vacuoles using transmission electron microscopy (TEM) and immunocytochemistry techniques. The results showed that ~50% of the analyzed human sperm cells (n = 1908; 17 normozoospermic human donors) contained vacuoles mainly located (80%) in the tip head region. A significant positive correlation was found between the sperm vacuole and nucleus areas. Furthermore, it was confirmed that nuclear vacuoles were invaginations of the nuclear envelope from the perinuclear theca and containing cytoskeletal proteins and cytoplasmic enzyme, discarding a nuclear or acrosomal origin. According to our findings, these human sperm head vacuoles are cellular structures originating from nuclear invaginations and contain perinuclear theca (PT) components, allowing us to define a new term of 'nuclear invaginations' rather than 'nuclear vacuoles'.

Human in vitro spermatogenesis as a regenerative therapy - where do we stand?

Spermatogenesis involves precise temporal and spatial gene expression and cell signalling to reach a coordinated balance between self-renewal and differentiation of spermatogonial stem cells through various germ cell states including mitosis, and meiosis I and II, which result in the generation of haploid cells with a unique genetic identity. Subsequently, these round spermatids undergo a series of morphological changes to shed excess cytoplast, develop a midpiece and tail, and undergo DNA repackaging to eventually form millions of spermatozoa. The goal of recreating this process in vitro has been pursued since the 1920s as a tool to treat male factor infertility in patients with azoospermia. Continued advances in reproductive bioengineering led to successful generation of mature, functional sperm in mice and, in the past 3 years, in humans. Multiple approaches to study human in vitro spermatogenesis have been proposed, but technical and ethical obstacles have limited the ability to complete spermiogenesis, and further work is needed to establish a robust culture system for clinical application.

The ribosome inhibitor chloramphenicol induces motility deficits in human spermatozoa: A proteomic approach identifies potentially involved proteins

Mature spermatozoa are almost completely devoid of cytoplasm; as such it has long been believed that they do not contain ribosomes and are therefore not capable of synthesising proteins. However, since the 1950s, various studies have shown translational activity within spermatozoa, particularly during their in vitro capacitation. But the type of ribosomes involved (cytoplasmic or mitochondrial) is still debated. Here, we investigate the presence and activity of the two types of ribosomes in mature human spermatozoa. By targeting ribosomal RNAs and proteins, we show that both types of ribosomes are localized in the midpiece as well as in the neck and the base of the head of the spermatozoa. We assessed the impact of cycloheximide (CHX) and chloramphenicol (CP), inhibitors of cytoplasmic and mitochondrial ribosomes, respectively, on different sperm parameters. Neither CHX, nor CP impacted sperm vitality, mitochondrial activity (measured through the ATP content), or capacitation (measured through the content in phosphotyrosines). However, increasing CP concentrations induced a decrease in total and progressive motilities as well as on some kinematic parameters while no effect was observed with CHX. A quantitative proteomic analysis was performed by mass spectrometry in SWATH mode to compare the proteomes of spermatozoa capacitated in the absence or presence of the two ribosome inhibitors. Among the ∼700 proteins identified in the different tested conditions, 3, 3 and 25 proteins presented a modified abundance in the presence of 1 and 2 mg/ml of CHX, and 1 mg/ml of CP, respectively. The observed abundance variations of some CP-down regulated proteins were validated using Multiple-Reaction Monitoring (MRM). Taken together, our results are in favor of an activity of mitochondrial ribosomes. Their inhibition by CP results in a decrease in the abundance of several proteins, at least FUNDC2 and QRICH2, and consequently induces sperm motility deficits.

The perinuclear theca protein Calicin helps shape the sperm head and maintain the nuclear structure in mice

The perinuclear theca (PT) is a cytoskeletal element encapsulating the sperm nucleus; however, our understanding of the physiological roles of PT in sperm is very limited. We show that Calicin interacts with itself and many other PT components, indicating it may serve as an organizing center of the PT assembly. Calicin is detectable first when surrounding the acrosome, then detected around the entire nucleus, and finally translocated to the postacrosomal region of spermatid heads. Intriguingly, loss of Calicin specifically causes surface subsidence of sperm heads in the nuclear condensation stage. Calicin interacts with inner acrosomal membrane (IAM) protein Spaca1 and nuclear envelope (NE) components to form an "IAM-PT-NE" structure. Intriguingly, Ccin-knockout sperm also exhibit DNA damage and failure of fertilization. Our study provides solid animal evidence to suggest that the PT encapsulating sperm nucleus helps shape the sperm head and maintain the nuclear structure.

Loss of perinuclear theca ACTRT1 causes acrosome detachment and severe male subfertility in mice

The perinuclear theca (PT) is a cytoskeletal element encapsulating the sperm nucleus; however, the physiological roles of the PT in sperm are largely uncertain. Here, we reveal that ACTRT1, ACTRT2, ACTL7A and ACTL9 proteins interact to form a multimeric complex and localize to the subacrosomal region of spermatids. Furthermore, we engineered Actrt1-knockout (KO) mice to define the functions of ACTRT1. Despite normal sperm count and motility, Actrt1-KO males were severely subfertile owing to a deficiency in fertilization. Loss of ACTRT1 caused a high incidence of malformed heads and detachment of acrosomes from sperm nuclei, caused by loosened acroplaxome structure during spermiogenesis. Furthermore, Actrt1-KO sperm showed reduced ACTL7A and PLCζ protein content as a potential cause of fertilization defects. Moreover, we reveal that ACTRT1 anchors developing acrosomes to the nucleus, likely by interacting with the inner acrosomal membrane protein SPACA1 and the nuclear envelope proteins PARP11 and SPATA46. Loss of ACTRT1 weakened the interaction between ACTL7A and SPACA1. Our study and recent findings of ACTL7A/ACTL9-deficient sperm together reveal that the sperm PT-specific ARP complex mediates the acrosome-nucleus connection.

High Resolution Proteomic Analysis of Subcellular Fractionated Boar Spermatozoa Provides Comprehensive Insights Into Perinuclear Theca-Residing Proteins

The perinuclear theca (PT) is a highly condensed, largely insoluble protein structure that surrounds the nucleus of eutherian spermatozoa. Recent reports have indicated that the PT unexpectedly houses several somatic proteins, such as core histones, which may be important post-fertilization during re-modelling of the male pronucleus, yet little is known regarding the overall proteomic composition of the PT. Here, we report the first in depth, label-free proteomic characterization of the PT of boar spermatozoa following the implementation of a long-established subcellular fractionation protocol designed to increase the detection of low abundance proteins. A total of 1,802 proteins were identified, a result that represents unparalleled depth of coverage for the boar sperm proteome and exceeds the entire annotated proteome of the Sus scrofa species so far. In the PT structure itself, we identified 813 proteins and confirmed the presence of previously characterized PT proteins including the core histones H2A, H2B, H3 and H4, as well as Ras-related protein Rab-2A (RAB2A) and Rab-2B (RAB2B) amongst other RAB proteins. In addition to these previously characterized PT proteins, our data revealed that the PT is replete in proteins critical for sperm-egg fusion and egg activation, including: Izumo family members 1–4 (IZUMO1-4) and phosphoinositide specific phospholipase ζ (PLCZ1). Through Ingenuity Pathway Analysis, we found surprising enrichment of endoplasmic reticulum (ER) proteins and the ER-stress response in the PT. This is particularly intriguing as it is currently held that the ER structure is lost during testicular sperm maturation. Using the String and Cytoscape tools to visualize protein-protein interactions revealed an intricate network of PT protein complexes, including numerous proteasome subunits. Collectively, these data suggest that the PT may be a unique site of cellular homeostasis that houses an abundance of protein degradation machinery. This fits with previous observations that the PT structure dissociates first within the oocyte post-fertilization. It remains to be explored whether proteasome subunits within the PT actively assist in the protein degradation of paternal cell structures post-fertilization and how aberrations in PT protein content may delay embryonic development.

KATNB1 is a master regulator of multiple katanin enzymes in male meiosis and haploid germ cell development

Katanin microtubule-severing enzymes are crucial executers of microtubule regulation. Here, we have created an allelic loss-of-function series of the katanin regulatory B-subunit KATNB1 in mice. We reveal that KATNB1 is the master regulator of all katanin enzymatic A-subunits during mammalian spermatogenesis, wherein it is required to maintain katanin A-subunit abundance. Our data shows that complete loss of KATNB1 from germ cells is incompatible with sperm production, and we reveal multiple new spermatogenesis functions for KATNB1, including essential roles in male meiosis, acrosome formation, sperm tail assembly, regulation of both the Sertoli and germ cell cytoskeletons during sperm nuclear remodelling, and maintenance of seminiferous epithelium integrity. Collectively, our findings reveal that katanins are able to differentially regulate almost all key microtubule-based structures during mammalian male germ cell development, through the complexing of one master controller, KATNB1, with a 'toolbox' of neofunctionalised katanin A-subunits.

Core Histones Are Constituents of the Perinuclear Theca of Murid Spermatozoa: An Assessment of Their Synthesis and Assembly during Spermiogenesis and Function after Gametic Fusion

The perinuclear theca (PT) of the eutherian sperm head is a cytoskeletal-like structure that houses proteins involved in important cellular processes during spermiogenesis and fertilization. Building upon our novel discovery of non-nuclear histones in the bovine PT, we sought to investigate whether this PT localization was a conserved feature of eutherian sperm. Employing cell fractionation, immunodetection, mass spectrometry, qPCR, and intracytoplasmic sperm injections (ICSI), we examined the localization, developmental origin, and functional potential of histones from the murid PT. Immunodetection localized histones to the post-acrosomal sheath (PAS) and the perforatorium (PERF) of the PT but showed an absence in the sperm nucleus. MS/MS analysis of selectively extracted PT histones indicated that predominately core histones (i.e., H3, H3.3, H2B, H2A, H2AX, and H4) populate the murid PT. These core histones appear to be de novo-synthesized in round spermatids and assembled via the manchette during spermatid elongation. Mouse ICSI results suggest that early embryonic development is delayed in the absence of PT-derived core histones. Here, we provide evidence that core histones are de novo-synthesized prior to PT assembly and deposited in PT sub-compartments for subsequent involvement in chromatin remodeling of the male pronucleus post-fertilization.

Characterization of different oligomeric forms of CRISP2 in the perinuclear theca versus the fibrous tail structures of boar spermatozoa

Mammalian sperm carry a variety of highly condensed insoluble protein structures such as the perinuclear theca, the fibrous sheath and the outer dense fibers, which are essential to sperm function. We studied the role of cysteine rich secretory protein 2 (CRISP2); a known inducer of non-pathological protein amyloids, in pig sperm with a variety of techniques. CRISP2, which is synthesized during spermatogenesis, was localized by confocal immunofluorescent imaging in the tail and in the post-acrosomal region of the sperm head. High resolution localization by immunogold labeling electron microscopy (EM) of ultrathin cryosections revealed that CRISP2 was present in the perinuclear theca and neck region of the sperm head, as well as in the outer dense fibers and the fibrous sheath of the sperm tail. Interestingly, we found that under native, non-reducing conditions CRISP2 formed oligomers both in the tail and the head but with different molecular weights and different biochemical properties. The tail oligomers were insensitive to reducing conditions but nearly complete dissociated into monomers under 8 M urea treatment, while the head 250 kDa CRISP2 positive oligomer completely dissociated into CRISP2 monomers under reducing conditions. The head specific dissociation of CRISP2 oligomer is likely a result of the reduction of various sulfhydryl groups in the cysteine rich domain of this protein. The sperm head CRISP2 shared typical solubilization characteristics with other perinuclear theca proteins as was shown with sequential detergent and salt treatments. Thus, CRISP2 is likely to participate in the formation of functional protein complexes in both the sperm tail and sperm head, but with differing oligomeric organization and biochemical properties. Future studies will be devoted to the understand the role of CRISP2 in sperm protein complexes formation and how this contributes to the fertilization processes.

Sperm-oocyte interplay: an overview of spermatozoon's role in oocyte activation and current perspectives in diagnosis and fertility treatment

The fertilizing spermatozoon is a highly specialized cell that selects from millions along the female tract until the oocyte. The paternal components influence the oocyte activation during fertilization and are fundamental for normal embryo development; however, the sperm-oocyte interplay is in a continuous debate. This review aims to analyze the available scientific information related to the role of the male gamete in the oocyte activation during fertilization, the process of the interaction of sperm factors with oocyte machinery, and the implications of any alterations in this interplay, as well as the advances and limitations of the reproductive techniques and diagnostic tests. At present, both PLCζ and PAWP are the main candidates as oocyte activated factors during fertilization. While PLCζ mechanism is via IP₃, how PAWP activates the oocyte still no clear, and these findings are important to study and treat fertilization failure due to oocyte activation, especially when one of the causes is the deficiency of PLCζ in the sperm. However, no diagnostic test has been developed to establish the amount of PLCζ, the protocol to treat this type of pathologies is broad, including treatment with ionophores, sperm selection improvement, and microinjection with PLCζ protein or RNA.

Regulation of Human Spermatogenesis

Human spermatogenesis (HS) is an intricate network of sequential processes responsible for the production of the male gamete, the spermatozoon. These processes take place in the seminiferous tubules (ST) of the testis, which are small tubular structures considered the functional units of the testes. Each human testicle contains approximately 600-1200 STs [1], and are capable of producing up to 275 million spermatozoa per day [2].

Haploid male germ cells-the Grand Central Station of protein transport

BACKGROUND

The precise movement of proteins and vesicles is an essential ability for all eukaryotic cells. Nowhere is this more evident than during the remarkable transformation that occurs in spermiogenesis-the transformation of haploid round spermatids into sperm. These transformations are critically dependent upon both the microtubule and the actin cytoskeleton, and defects in these processes are thought to underpin a significant percentage of human male infertility.

OBJECTIVE AND RATIONALE

This review is aimed at summarising and synthesising the current state of knowledge around protein/vesicle transport during haploid male germ cell development and identifying knowledge gaps and challenges for future research. To achieve this, we summarise the key discoveries related to protein transport using the mouse as a model system. Where relevant, we anchored these insights to knowledge in the field of human spermiogenesis and the causality of human male infertility.

SEARCH METHODS

Relevant studies published in English were identified using PubMed using a range of search terms related to the core focus of the review-protein/vesicle transport, intra-flagellar transport, intra-manchette transport, Golgi, acrosome, manchette, axoneme, outer dense fibres and fibrous sheath. Searches were not restricted to a particular time frame or species although the emphasis within the review is on mammalian spermiogenesis.

OUTCOMES

Spermiogenesis is the final phase of sperm development. It results in the transformation of a round cell into a highly polarised sperm with the capacity for fertility. It is critically dependent on the cytoskeleton and its ability to transport protein complexes and vesicles over long distances and often between distinct cytoplasmic compartments. The development of the acrosome covering the sperm head, the sperm tail within the ciliary lobe, the manchette and its role in sperm head shaping and protein transport into the tail, and the assembly of mitochondria into the mid-piece of sperm, may all be viewed as a series of overlapping and interconnected train tracks. Defects in this redistribution network lead to male infertility characterised by abnormal sperm morphology (teratozoospermia) and/or abnormal sperm motility (asthenozoospermia) and are likely to be causal of, or contribute to, a significant percentage of human male infertility.

WIDER IMPLICATIONS

A greater understanding of the mechanisms of protein transport in spermiogenesis offers the potential to precisely diagnose cases of male infertility and to forecast implications for children conceived using gametes containing these mutations. The manipulation of these processes will offer opportunities for male-based contraceptive development. Further, as increasingly evidenced in the literature, we believe that the continuous and spatiotemporally restrained nature of spermiogenesis provides an outstanding model system to identify, and de-code, cytoskeletal elements and transport mechanisms of relevance to multiple tissues.

NEDD4-like ubiquitin ligase 2 protein (NEDL2) in porcine spermatozoa, oocytes, and preimplantation embryos and its role in oocyte fertilization†

The ubiquitin-proteasome system plays diverse regulatory and homeostatic roles in mammalian reproduction. Ubiquitin ligases are the substrate-specific mediators of ubiquitin-binding to its substrate proteins. The NEDD4-like ubiquitin ligase 2 (aliases NEDL2, HECW2) is a HECT-type ubiquitin ligase that contains one N-terminal HECW ubiquitin ligase domain, one C-terminal HECT ubiquitin ligase domain, one C2 domain, and two WW protein-protein interaction modules. Beyond its predicted ubiquitin-ligase activity, its cellular functions are largely unknown. Current studies were designed to investigate the content and distribution of NEDL2 in porcine spermatozoa, oocytes, zygotes, and early preimplantation embryos, and in cumulus cells before and after in vitro maturation with oocytes, and fibroblast cells as positive control by western blot and immunocytochemistry, and to examine its roles during oocyte fertilization. Multiple isoforms of NEDL2 were identified by WB. One at approximately 52 kDa was detected only in the germinal vesicle (GV) stage and metaphase II oocytes, and in early preimplantation embryos. Other isoforms were high mass bands at 91, 136, and 155 kDa, which were only detected in somatic cells. Interestingly, ejaculated spermatozoa prominently displayed the same 52 kDa band as oocytes; they also had two minor bands of 74 and 129 kDa, which were not detected in somatic cells or oocytes. By immunofluorescence, NEDL2 showed a diffused cytoplasmic localization in all cell types and accumulated in distinct foci in the germinal vesicles (GVs) of immature oocytes, in maternal and paternal pronuclei of zygotes and nuclei of embryo blastomeres and somatic cells. In blastocysts, the labeling intensity of NEDL2 was stronger in the inner cell mass than in trophoblast, indicating higher NEDL2 content in the ICM cells than in trophectoderm. NEDL2 abundance was 10 times higher in post-maturation oocyte-surrounding cumulus cells than that of cumulus cells before in vitro maturation with hormones, indicating that NEDL2 may have a unique role in cumulus cells after ovulation. Microinjection of anti-NEDL2 antibody into oocyte before IVF did not affect the percentage of oocytes fertilized, percentage of oocytes cleaved, or blastocyst formation. However, the anti-NEDL2 antibody decreased the number of pronuclei, accelerated the formation of nuclear precursor bodies at 6 h postfertilization, inhibited sperm DNA decondensation, and resulted in more fertilized oocytes without male pronuclear formation. In summary, NEDL2 may play a key role during fertilization, especially during sperm DNA decondensation.

Sperm-borne glutathione-S-transferase omega 2 accelerates the nuclear decondensation of spermatozoa during fertilization in mice†

The postacrosomal sheath (PAS) of the perinuclear theca (PT) is the first compartment of the sperm head to solubilize into the ooplasm upon sperm-oocyte fusion, implicating its constituents in zygotic development. This study investigates the role of one such constituent, glutathione-S-transferase omega 2 (GSTO2), an oxidative-reductive enzyme found in the PAS and perforatorial regions of the PT. GSTO2 uses the conjugation of reduced glutathione, an electron donor shown to be compulsory in sperm disassembly within the ooplasm. The proximity of GSTO2 to the condensed sperm nucleus led us to hypothesize that this enzyme may facilitate nuclear decondensation by reducing disulfide bonds before the recruitment of GSTO enzymes from within the ooplasm. To test this hypothesis, we utilized a cell permeable isozyme-specific inhibitor, which fluoresces when bound to the active site of GSTO2, to functionally inhibit spermatozoa before performing intracytoplasmic sperm injections (ICSI) in mice. The technique allowed for targeted inhibition of solely PT-residing GSTO2, as all that is required for complete zygotic development is the injection of the mouse spermatozoon head. ICSI showed that inhibition of PT-anchored GSTO2 caused a delay in sperm nuclear decondensation, and further resulted in untimely embryo cleavage, and an increase in fragmentation beginning at the morula stage. The confounding effects of these developmental delays ultimately resulted in decreased blastocyst formation. This study implicates PT-anchored GSTO2 as an important facilitator of nuclear decondensation and reinforces the notion that the PAS-PT is a critical sperm compartment harboring molecules that facilitate zygotic development.

The perforatorium and postacrosomal sheath of rat spermatozoa share common developmental origins and protein constituents†

The perinuclear theca (PT) is a cytosolic protein capsule that surrounds the nucleus of eutherian spermatozoa. Compositionally, it is divided into two regions: the subacrosomal layer (SAL) and the postacrosomal sheath (PAS). In falciform spermatozoa, a third region of the PT emerges that extends beyond the nuclear apex called the perforatorium. The formation of the SAL and PAS differs, with the former assembling early in spermiogenesis concomitant with acrosome formation, and the latter dependent on manchette descent during spermatid elongation. The perforatorium also forms during the elongation phase of spermiogenesis, suggesting that like the PAS, its assembly is facilitated by the manchette. The temporal similarity in biogenesis between the PAS and perforatorium led us to compare their molecular composition using cell fractionation and immunodetection techniques. Although the perforatorium is predominantly composed of its endemic protein FABP9/PERF15, immunolocalization indicates that it also shares proteins with the PAS. These include WBP2NL/PAWP, WBP2, GSTO2, and core histones, which have been implicated in early fertilization and zygotic events. The compositional homogeny between the PAS and perforatorium supports our observation that their development is linked. Immunocytochemistry indicates that both PAS and perforatorial biogenesis depend on the transport and deposition of cytosolic proteins by the microtubular manchette. Proteins translocated from the manchette pass ventrally along the spermatid head into the apical perforatorial space prior to PAS deposition in the wake of manchette descent. Our findings demonstrate that the perforatorium and PAS share a mechanism of developmental assembly and thereby contain common proteins that facilitate fertilization.

How defective spermatogenesis affects sperm DNA integrity

Spermatogenesis is the essential process to maintain and promote male fertility. It is extraordinarily complex with many regulatory elements and numerous steps. The process involves several cell types, regulatory molecules, repair mechanisms and epigenetic regulators. Evidence has shown that fertility can be negatively impacted by reduced sperm DNA integrity. Sources of sperm DNA damage include replication errors and causes of DNA fragmentation which include abortive apoptosis, defective maturation and oxidative stress. This review outlines the process of spermatogenesis, spermatogonial regulation and sperm differentiation; additionally, DNA damage and currently studied DNA repair mechanisms in spermatozoon are also covered.

Ultra-imaging in applied animal andrology: The power and the beauty

Ultrastructural studies of the male gamete provide relevant complementary data of value for the clinical assessment of semen quality and assist in determining phylogenetic and structural/functional relationships. This is illustrated using semen samples and testicular material from vulnerable wild animals (cheetah and rhinoceros), commercially exploited exotic birds (ratites and tinamou) and poultry (chicken and duck). Transmission electron microscopy (TEM) was employed to record sperm and spermatid ultrastructural detail on a comparative basis. The power of the technique was demonstrated using normal and abnormal (the knobbed acrosome defect) formation of the acrosome in the cheetah and rhinoceros. The structural similarities of the defect across species was apparent. The determination of phylogenetic associations was illustrated by comparing structural characteristics between ratites (ostrich, emu and rhea), the tinamou and poultry (chicken and duck), highlighting the morphological peculiarities evident in the midpiece and proximal principal piece of the sperm tail. A clear distinction was obvious between the ratites and tinamou on the one hand and the Galliform and Anseriform birds on the other. The potential power of using molecular techniques in conjunction with ultrastructural studies to explain structural/functional relationships was demonstrated by describing a transient elaboration of the perinuclear theca that occurs during a specific stage of spermiogenesis in ratites, and which can only be imaged using TEM. The inherent aesthetic appeal of the structurally complex normal and defective male gamete was also emphasised.

Abnormal fertility, acrosome formation, IFT20 expression and localization in conditional Gmap210 knockout mice

GMAP210 (TRIP11) is a cis-Golgi network-associated protein and a Golgi membrane receptor for IFT20, an intraflagellar transport component essential for male fertility and spermiogenesis in mice. To investigate the role of GMAP210 in male fertility and spermatogenesis, floxed Gmap210 mice were bred with Stra8-iCre mice so that the Gmap210 gene is disrupted in spermatocytes and spermatids in this study. The Gmap210flox/flox: Stra8-iCre mutant mice showed no gross abnormalities and survived to adulthood. In adult males, testis and body weights showed no difference between controls and mutant mice. Low-magnification histological examination of the testes revealed normal seminiferous tubule structure, but sperm counts and fertility were significantly reduced in mutant mice compared with controls. Higher resolution examination of the mutant seminiferous epithelium showed that nearly all sperm had more oblong, abnormally shaped heads, while the sperm tails appeared to have normal morphology. Electron microscopy also revealed abnormally shaped sperm heads but normal axoneme core structure; some sperm showed membrane defects in the midpiece. In mutant mice, expression levels of IFT20 and other selective acrosomal proteins were significantly reduced, and their localization was also affected. Peanut-lectin, an acrosome maker, was almost absent in the spermatids and epididymal sperm. Mitochondrion staining was highly concentrated in the heads of sperm, suggesting that the midpieces were coiling around or aggregating near the heads. Defects in acrosome biogenesis were further confirmed by electron microscopy. Collectively, our findings suggest that GMAP210 is essential for acrosome biogenesis, normal mitochondrial sheath formation, and male fertility, and it determines expression levels and acrosomal localization of IFT20 and other acrosomal proteins.

The alteration of PLCζ protein expression in unexplained infertile and asthenoteratozoospermic patients: A potential effect on sperm fertilization ability

Failed oocyte activation has been observed in unexplained infertile (UI) and asthenoteratozoospermic (AT) men. The deficiency of phospholipase C-zeta (PLCζ) could be a possible reason for such failures and has not been studied yet. We investigated the expression and localization of PLCζ protein in the sperms of patients with UI and AT conditions. The relationships between PLCζ-related parameters with male age, sperm characteristics, DNA integrity, and cellular maturity were assessed. Semen samples were collected from fertile (n = 40), UI (n = 40), and AT (n = 40) men. Subsequently, semen analysis, DNA fragmentation, hyaluronic acid-binding ability, and PLCζ level along with its distribution were evaluated using computer-assisted sperm analyzer, sperm chromatin structure assay (SCSA), hyaluronic acid-binding assay (HBA), western blot analysis and immunofluorescence microscopy, respectively. Unlike SCSA, the values of HBA, and PLCζ expression were significantly reduced in UI and AT patients compared to fertile men, whereas no significant differences were observed among the experimental groups in terms of PLCζ localization patterns. The regression analysis also showed that HBA is the only variable associated with PLCζ levels. Furthermore, the correlation of male age with PLCζ localization in postacrosomal, equatorial, and acrosomal+postacrosomal+equatorial (A+PA+E) patterns, as well as the relation of normal morphology, with the (A+PA+E) pattern, remained in the regression model. Our findings indicated that reduced PLCζ level along with the increased DNA fragmentation and impaired maturation may be possible etiologies of decreased fertilization in the studied subjects.

WBP2 shares a common location in mouse spermatozoa with WBP2NL/PAWP and like its descendent is a candidate mouse oocyte-activating factor

The sperm-borne oocyte-activating factor (SOAF) resides in the sperm perinuclear theca (PT). A consensus has been reached that SOAF most likely resides in the postacrosomal sheath (PAS), which is the first region of the PT to solubilize upon sperm–oocyte fusion. There are two SOAF candidates under consideration: PLCZ1 and WBP2NL. A mouse gene germline ablation of the latter showed that mice remain fertile with no observable phenotype despite the fact that a competitive inhibitor of WBP2NL, derived from its PPXY motif, blocks oocyte activation when coinjected with WBP2NL or spermatozoa. This suggested that the ortholog of WBP2NL, WBP2, containing the same domain and motifs associated with WBP2NL function, might compensate for its deficiency in oocyte activation. Our objectives were to examine whether WBP2 meets the developmental criteria established for SOAF and whether it has oocyte-activating potential. Immunoblotting detected WBP2 in mice testis and sperm and immunofluorescence localized WBP2 to the PAS and perforatorium of the PT. Immunohistochemistry of the testes revealed that WBP2 reactivity was highest in round spermatids and immunofluorescence detected WBP2 in the cytoplasmic lobe of elongating spermatids and colocalized it with the microtubular manchette during PT assembly. Microinjection of the recombinant forms of WBP2 and WBP2NL into metaphase II mouse oocytes resulted in comparable rates of oocyte activation. This study shows that WBP2 shares a similar testicular developmental pattern and location with WBP2NL and a shared ability to activate the oocyte, supporting its consideration as a mouse SOAF component that can compensate for a WBP2NL.

The developmental origin and compartmentalization of glutathione-s-transferase omega 2 isoforms in the perinuclear theca of eutherian spermatozoa

The perinuclear theca (PT) is a condensed, nonionic detergent resistant cytosolic protein layer encapsulating the sperm head nucleus. It can be divided into two regions: the subacrosomal layer, whose proteins are involved in acrosomal assembly during spermiogenesis, and the postacrosomal sheath (PAS), whose proteins are implicated in sperm–oocyte interactions during fertilization. In continuation of our proteomic analysis of the PT, we have isolated two prominent PT-derived proteins of 28 and 31 kDa from demembranated bovine sperm head fractions. These proteins were identified by mass spectrometry as isoforms of glutathione-s-transferase omega 2 (GSTO2). Immunoblots probed with anti-GSTO2 antibodies confirmed the presence of the GSTO2 isoforms in these fractions while fluorescent immunocytochemistry localized the isoforms to the PAS region of the bull, boar, and murid PT. In addition to the PAS labeling of GSTO2, the performatorium of murid spermatozoa was also labeled. Immunohistochemistry of rat testes revealed that GSTO2 was expressed in the third phase of spermatogenesis (i.e., spermiogenesis) and assembled in the PAS and perforatorial regions of late elongating spermatids. Fluorescent immunocytochemistry performed on murine testis cells co-localized GSTO2 and tubulin on the transient microtubular-manchette of elongating spermatids. These findings imply that GSTO2 is transported and deposited in the PAS region by the manchette, conforming to the pattern of assembly found with other PAS proteins. The late assembly of GSTO2 and its localization in the PAS suggests a role in regulating the oxidative and reductive state of covalently linked spermatid/sperm proteins, especially during the disassembly of the sperm accessory structures after fertilization.

Review: Sperm-oocyte interactions and their implications for bull fertility, with emphasis on the ubiquitin-proteasome system

Fertilization is an intricate cascade of events that irreversibly alter the participating male and female gamete and ultimately lead to the union of paternal and maternal genomes in the zygote. Fertilization starts with sperm capacitation within the oviductal sperm reservoir, followed by gamete recognition, sperm-zona pellucida interactions and sperm-oolemma adhesion and fusion, followed by sperm incorporation, oocyte activation, pronuclear development and embryo cleavage. At fertilization, bull spermatozoon loses its acrosome and plasma membrane components and contributes chromosomes, centriole, perinuclear theca proteins and regulatory RNAs to the zygote. While also incorporated in oocyte cytoplasm, structures of the sperm tail, including mitochondrial sheath, axoneme, fibrous sheath and outer dense fibers are degraded and recycled. The ability of some of these sperm contributed components to give rise to functional zygotic structures and properly induce embryonic development may vary between bulls, bearing on their reproductive performance, and on the fitness, health, fertility and production traits of their offspring. Proper functioning, recycling and remodeling of gamete structures at fertilization is aided by the ubiquitin-proteasome system (UPS), the universal substrate-specific protein recycling pathway present in bovine and other mammalian oocytes and spermatozoa. This review is focused on the aspects of UPS relevant to bovine fertilization and bull fertility.

Impact of a mild scrotal heating on sperm chromosomal abnormality, acrosin activity and seminal alpha-glucosidase in human fertile males

The aim of this study was to observe sperm aneuploidy, DNA integrity, seminal alpha-glucosidase (NAG) and acrosin activity (AA) under testicular heat stress (SH). Spermatozoa were obtained from 30 healthy adult volunteers subjected to scrotal warming at 43°C for 30-40 min on two successive days per week for 3 months between February 2012 and September 2016. Aniline blue (AB), acridine orange (AO) staining, TUNEL assay and FISH analysis to evaluate sperm function, sperm DNA integrity and chromosomal abnormalities were carried on before, during and after SH. Sperm AA and NAG was measured by microplate reader. The mean parameters of sperm parameters, AA and NAG were significantly decreased. In contrast, the mean percentage of sperm DNA fragmentation and the proportion of aneuploidy of chromosomes 13, 18, 21, X and Y were significantly increased for spermatozoa collected during SH versus before SH (p < .01-.001). After stopping scrotal heating for 3 months, most parameters were completely restored to pre-SH levels. Sperm parameters, sperm DNA integrity, chromosomes, AA and NAG are affected by scrotal exposure to constant SH temperatures several degrees over normal physiological temperature, and after treatment, these parameters were reversibly restored to the level before SH in adult men.

Sperm-derived factors enhance the in vitro developmental potential of haploid parthenotes

Parthenotes are characterized by poor in vitro developmental potential either due to the ploidy status or the absence of paternal factors. In the present study, we demonstrate the beneficial role of sperm-derived factors (SDF) on the in vitro development of mouse parthenotes. Mature (MII) oocytes collected from superovulated Swiss albino mice were activated using strontium chloride (SrCl2) in the presence or absence of various concentrations of SDF in M16 medium. The presence of SDF in activation medium did not have any significant influence on the activation rate. However, a significant increase in the developmental potential of the embryos and increased blastocyst rate (P < 0.01) was observed at 50 µg/ml concentration. Furthermore, the activated oocytes from this group exhibited early cleavage and cortical distribution of cortical granules that was similar to that of normally fertilized zygotes. Culturing 2-cell stage parthenotes in the presence of SDF significantly improved the developmental potential (P < 0.05) indicating that they also play a significant role in embryo development. In conclusion, artificial activation of oocytes with SDF can improve the developmental potential of parthenotes in vitro.

Prothymosin alpha expression in the vertebrate testis: a comparative review

Prothymosin alpha (PTMA) is a highly acidic, intrinsically disordered protein that was first extracted from rat thymus and characterized as an immunogenic factor but soon detected in a variety of mammalian tissues. The presence of a nuclear localization signal and the adoption of a peculiar random-coil conformation are among the reasons behind its interaction with several molecular partners, hence at this time PTMA is known to be a very conserved and widely expressed molecule, involved in numerous and diverse biological processes. Only few studies have tried to weigh its possible involvement in reproduction, specifically in male gametogenesis: first reports have suggested that PTMA might be associated with the proliferative and early-meiotic phases of mammal spermatogenesis. Some years later, a comparative project on vertebrate spermatogenesis reported the isolation, for the first time, of prothymosin in a non-mammalian species, the amphibian Pelophylax esculentus. PTMA transcript and protein are localized in the germinal compartment, from spermatocytes to spermatozoa. A congruent pattern has been highlighted in studies on the fish Torpedo marmorata and Danio rerio, and in the mammal Rattus norvegicus, in which the expression of PTMA has been found in meiotic and post-meiotic germ cells inside testicular cysts and tubules. Moreover, its presence has been confirmed in rat and human spermatozoa (associated with the acrosome); its retention in the apical region of the head after the acrosome reaction revealed a striking conservation of the pattern during phylogenesis and suggested a possible role for the protein in gametogenesis and in fertilization.

Phospholipase C zeta and calcium oscillations at fertilisation: The evidence, applications, and further questions

Oocyte activation is a fundamental event at mammalian fertilisation, initiated by a series of characteristic calcium (Ca²⁺) oscillations in mammals. This characteristic pattern of Ca²⁺ release is induced in a species-specific manner by a sperm-specific enzyme termed phospholipase C zeta (PLCζ). Reduction or absence of functional PLCζ within sperm underlies male factor infertility in humans, due to mutational inactivation or abrogation of PLCζ protein expression. Underlying such clinical implications, a significant body of evidence has now been accumulated that has characterised the unique biochemical and biophysical properties of this enzyme, further aiding the unique clinical opportunities presented. Herein, we present and discuss evidence accrued over the past decade and a half that serves to support the identity of PLCζ as the mammalian sperm factor. Furthermore, we also discuss the potential novel avenues that have yet to be examined regarding PLCζ mechanism of action in both the oocyte, and the sperm. Finally, we discuss the advances that have been made regarding the clinical therapeutic and diagnostic applications of PLCζ in potentially treating male infertility as a result of oocyte activation deficiency (OAD), and also possibly more general cases of male subfertility.

WW domain-binding protein 2: an adaptor protein closely linked to the development of breast cancer

The WW domain is composed of 38 to 40 semi-conserved amino acids shared with structural, regulatory, and signaling proteins. WW domain-binding protein 2 (WBP2), as a binding partner of WW domain protein, interacts with several WW-domain-containing proteins, such as Yes kinase-associated protein (Yap), paired box gene 8 (Pax8), WW-domain-containing transcription regulator protein 1 (TAZ), and WW-domain-containing oxidoreductase (WWOX) through its PPxY motifs within C-terminal region, and further triggers the downstream signaling pathway in vitro and in vivo. Studies have confirmed that phosphorylated form of WBP2 can move into nuclei and activate the transcription of estrogen receptor (ER) and progesterone receptor (PR), whose expression were the indicators of breast cancer development, indicating that WBP2 may participate in the progression of breast cancer. Both overexpression of WBP2 and activation of tyrosine phosphorylation upregulate the signal cascades in the cross-regulation of the Wnt and ER signaling pathways in breast cancer. Following the binding of WBP2 to the WW domain region of TAZ which can accelerate migration, invasion and is required for the transformed phenotypes of breast cancer cells, the transformation of epithelial to mesenchymal of MCF10A is activated, suggesting that WBP2 is a key player in regulating cell migration. When WBP2 binds with WWOX, a tumor suppressor, ER transactivation and tumor growth can be suppressed. Thus, WBP2 may serve as a molecular on/off switch that controls the crosstalk between E2, WWOX, Wnt, TAZ, and other oncogenic signaling pathways. This review interprets the relationship between WBP2 and breast cancer, and provides comprehensive views about the function of WBP2 in the regulation of the pathogenesis of breast cancer and endocrine therapy in breast cancer treatment.

Roles of cancer/testis antigens (CTAs) in breast cancer

Breast cancer is the most common cancer diagnosed and is the second leading cause of cancer death among women in the US. For breast cancer, early diagnosis and efficient therapy remains a significant clinical challenge. Therefore, it is necessary to identify novel tumor associated molecules to target for biomarker development and immunotherapy. In this regard, cancer testis antigens (CTAs) have emerged as a potential clinical biomarker targeting immunotherapy for various malignancies due to the nature of its characteristics. CTAs are a group of tumor associated antigens (TAAs) that display normal expression in immune-privileged organs, but display aberrant expression in several types of cancers, particularly in advanced cancers. Investigation of CTAs for the clinical management of breast malignancies indicates that these TAAs have potential roles as novel biomarkers, with increased specificity and sensitivity compared to those currently used in the clinic. Moreover, TAAs could be therapeutic targets for cancer immunotherapy. This review is an attempt to address the promising CTAs in breast cancer and their possible clinical implications as biomarkers and immunotherapeutic targets with particular focus on challenges and future interventions.

Evaluation of PLCζ and PAWP Expression in Globozoospermic Individuals

Objective

Globozoospermia is a rare type of teratozoospermia with incidence of 0.1% among infertile individuals. Phospholipase C zeta (PLCζ) and postacrosomal sheath WW domain binding protein (PAWP) are the main candidates in sperm taking responsibility for oocyte activation during fertilization. Therefore, we aimed to evaluate the expression of these two genes at RNA and protein levels in globozoospermic individuals and compare the results with fertile individuals.

Materials and Methods

In this experimental study, semen samples of 21 infertile men with globozoospermia and 25 fertile men were collected. Expression of PLCζ and PAWP at RNA and protein levels were assessed and compared between two groups by quantitative real time polymerase chain reaction (qPCR) and Western blot, respectively.

Results

Expression of both PLCζ and PAWP were significantly reduced at RNA and protein levels in infertile men with globozoospermia compared to fertile men.

Conclusion

This is the first study that simultaneously assessing the respective factors in a large population of globozoospermia, suggested that intra-cytoplasmic sperm injection (ICSI) along with artificial oocyte activation may rescue failed fertilization in routine ICSI.

Spermatogenesis in humans and its affecting factors

Spermatogenesis is an extraordinary complex process. The differentiation of spermatogonia into spermatozoa requires the participation of several cell types, hormones, paracrine factors, genes and epigenetic regulators. Recent researches in animals and humans have furthered our understanding of the male gamete differentiation, and led to clinical tools for the better management of male infertility. There is still much to be learned about this intricate process. In this review, the critical steps of human spermatogenesis are discussed together with its main affecting factors.

Negative biomarker based male fertility evaluation: Sperm phenotypes associated with molecular-level anomalies

Biomarker-based sperm analysis elevates the treatment of human infertility and ameliorates reproductive performance in livestock. The negative biomarker-based approach focuses on proteins and ligands unique to defective spermatozoa, regardless of their morphological phenotype, lending itself to analysis by flow cytometry (FC). A prime example is the spermatid specific thioredoxin SPTRX3/TXNDC8, retained in the nuclear vacuoles and superfluous cytoplasm of defective human spermatozoa. Infertile couples with high semen SPTRX3 are less likely to conceive by assisted reproductive therapies (ART) and more prone to recurrent miscarriage while low SPTRX3 has been associated with multiple ART births. Ubiquitin, a small, proteolysis-promoting covalent posttranslational protein modifier is found on the surface of defective posttesticular spermatozoa and in the damaged protein aggregates, the aggresomes of spermiogenic origin. Semen ubiquitin content correlates negatively with fertility and conventional semen parameters, and with sperm binding of lectins LCA (Lens culinaris agglutinin; reveals altered sperm surface) and PNA (Arachis hypogaea/peanut agglutinin; reveals acrosomal malformation or damage). The Postacrosomal Sheath WWI Domain Binding Protein (PAWP), implicated in oocyte activation during fertilization, is ectopic or absent from defective human and animal spermatozoa. Consequently, FC-parameters of PAWP correlate with ART outcomes in infertile couples and with fertility in bulls. Assays based on the above biomarkers have been combined into multiplex FC semen screening protocols, and the surface expression of lectins and ubiquitin has been utilized to develop nanoparticle-based bull semen purification method validated by field artificial insemination trials. These advances go hand-in-hand with the innovation of FC-technology and genomics/proteomics-based biomarker discovery.

Increased male fertility using fertility-related biomarkers

Conventional semen analyses are used to evaluate male factor fertility/infertility in humans and other animals. However, their clinical value remains controversial. Therefore, new tools that more accurately assess male fertility based on sperm function and fertilization mechanism are of interest worldwide. While protein markers in spermatozoa that might help differentiate fertile and infertile sperm have been identified, studies are in their infancy, and the markers require validation in field trials. In the present study, to discover more sensitive biomarkers in spermatozoa for predicting male fertility, we assessed protein expression in capacitated spermatozoa. The results demonstrated that cytochrome b-c1 complex subunit 2 (UQCRC2) was abundantly expressed in high-litter size spermatozoa (>3-fold). On the other hand, equatorin, beta-tubulin, cytochrome b-c1 complex subunit 1 (UQCRC1), speriolin, Ras-related protein Rab-2A (RAB2A), spermadhesin AQN-3, and seminal plasma sperm motility inhibitor were abundantly expressed in low-litter size spermatozoa (>3-fold). Moreover, RAB2A and UQCRC1 expression negatively correlated with litter size, while UQCRC2 expression positively correlated with litter size. Finally, the putative biomarkers predicted litter size in field trials. Our study suggests that biomarkers present in spermatozoa after capacitation can help differentiate superior male fertility from below-average fertility with high sensitivity.

Proteomic approaches for profiling negative fertility markers in inferior boar spermatozoa

The ability to predict male fertility is of paramount importance for animal breeding industries and for human reproduction. Conventional semen analysis generally provides information on the quantitative parameters of spermatozoa, but yields no information concerning its functional competence. Proteomics have identified candidates for male fertility biomarkers, but no studies have clearly identified the relationship between the proteome and sperm fertility. Therefore, we performed a proteomic analysis to investigate small and large litter size boar spermatozoa and identify proteins related to male fertility. In this study, 20 proteins showed differential expression levels in small and large litter size groups. Nineteen of these proteins exhibited decreased expression in large litter size samples and increased expression in the small litter group. Interestingly, only one protein was highly expressed in the large litter size spermatozoa. We then identified signaling pathways associated with the differentially expressed protein markers. Glutathione S-transferase Mu3 and glutathione peroxidase 4 were related to the glutathione metabolic pathway and arginine vasopressin receptor 2 was linked to vasopressin R2/STAT. In summary, this is the first study to consider negative fertility biomarkers, and the identified proteins could potentially be used as biomarkers for the detection of inferior male fertility.

Re: Is PAWP the 'real' sperm factor?

Mammalian embryo development is init iated by intracel lular Ca2+ oscillations that result in oocyte activation following gamete membrane fusion. It is widely believed that oocyte Ca2+ oscillations are triggered by a sperm-specific protein, phospholipase C-zeta (PLCζ) that activates InsP3 production leading to repetitive Ca2+ release from intracellular stores. However, a recent report in the FASEB Journal by Aarabi et al. challenges this view by proposing postacrosomal WW domain-binding protein (PAWP) as another sperm-derived protein that can also initiate Ca2+ oscillations and zygotic development at fertilization. Here we discuss these new findings and examine the evidence suggesting PAWP as the "real" sperm factor.