Unraveling the Impact of the PROCA1 Mutation in Male Infertility: Incorporating Whole Exome Sequencing in Teratozoospermia Patients and Analyzing Proca1 Knockout Mice

In the world, about 15% of couples are infertile, and nearly half of all infertility was caused by men. A large number of genetic mutations are thought to affect spermatogenesis by regulating acrosome formation. Here, we identified three patients harbouring the protein interacting with cyclin A1 (PROCA1) mutation by whole exome sequencing (WES) and Sanger sequencing among patients with predominantly acrosome-deficient teratozoospermia. However, the expression and roles of PROCA1 in infertile men remain unclear. We found that PROCA1 is predominantly expressed in the testis, where it is specifically localized to the acrosome of normal human sperm. Proca1 knockout (KO) mice were subsequently generated using CRISPR-Cas9 technology. However, Proca1 KO adult male mice were fertile, with testis-to-body weight ratios comparable to those of wild-type (WT) mice. Testicular tissue or sperm morphology were not significantly different in Proca1 KO mice compared to WT mice. Expression of the acrosome markers PNA and SP56 in the acrosome was comparable between Proca1 KO and WT mice. In summary, these findings suggested that the PROCA1 mutation identified in humans does not affect acrosome biogenesis in mice.

Molecular insights into sperm head shaping and its role in human male fertility

BACKGROUND

Sperm head shaping, controlled by the acrosome-acroplaxome-manchette complex, represents a significant morphological change during spermiogenesis and involves numerous proteins expressed in a spatially and temporally specific manner. Defects in sperm head shaping frequently lead to teratozoospermia concomitant with oligozoospermia and asthenozoospermia, but the pathogenic mechanism underlying sperm head shaping, and its role in male infertility, remain poorly understood.

OBJECTIVE AND RATIONALE

This review aims to summarize the mechanism underlying sperm head shaping, reveal the relationship between gene defects associated with sperm head shaping and male infertility in humans and mice, and explore potential clinical improvements in ICSI treatment.

SEARCH METHODS

We searched the PubMed database for articles published in English using the keyword 'sperm head shaping' in combination with the following terms: 'acrosome formation', 'proacrosomal vesicles (PAVs)', 'manchette', 'perinuclear theca (PT)', 'chromatin condensation', 'linker of nucleoskeleton and cytoskeleton (LINC) complex', 'histone-to-protamine (HTP) transition', 'male infertility', 'ICSI', and 'artificial oocyte activation (AOA)'. The selected publications until 1 August 2024 were critically summarized, integrated, and thoroughly discussed, and the irrelevant literature were excluded.

OUTCOMES

A total of 6823 records were retrieved. After careful screening, integrating relevant literature, and excluding articles unrelated to the topic of this review, 240 articles were ultimately included in the analysis. Firstly, we reviewed the important molecular events and structures integral to sperm head shaping, including PAV formation to fusion, acrosome attachment to the nucleus, structure and function of the manchette, PT, chromatin condensation, and HTP transition. Then, we set forth human male infertility associated with sperm head shaping and identified genes related to sperm head shaping resulting in teratozoospermia concomitant with oligozoospermia and asthenozoospermia. Finally, we summarized the outcomes of ICSI in cases of male infertility resulting from mutations in the genes associated with sperm head shaping, as well as the ICSI outcomes through AOA for infertile men with impaired sperm head.

WIDER IMPLICATIONS

Understanding the molecular mechanisms of sperm head shaping and its relationship with human male infertility holds profound clinical implications, which may contribute to risk prediction, genetic diagnosis, and the potential treatment of human male infertility.

Sperm acrosome-associated 1 (SPACA1) mRNA and protein molecules deficiency indicate low fertility and semen quality of Bali bulls (Bos sondaicus)

Molecular-based biomarkers are believed to be more accurate in determining bulls' fertility and sperm's various fertility characteristics. The sperm acrosome-associated 1 (SPACA1) molecule, located in the anterior acrosomal and equatorial segments of the sperm head, is thought to be related to the function of binding and fusion between sperm and oocyte. This study aims to analyze the association of SPACA1 mRNA and protein with the fertility rate and semen quality of Bali bulls (Bos sondaicus) and assess its potential as a potential molecular biomarker determining bull fertility and sperm quality. Frozen semen from 20 Bali bulls was used in the research, which was then divided into two groups: high (HF) and low fertility (LF). SPACA1 mRNA abundance was analyzed using qRT-PCR, and SPACA1 protein abundance was analyzed using EIA. The semen quality parameters analyzed were motility (CASA), plasma membrane integrity (HOS test), sperm head morphology abnormalities (William staining), sperm viability (SYBR 14-PI), sperm capacitation (CTC assay), and sperm acrosome integrity (FITC-PNA). The results showed that there was a significant difference (P < 0.05) between high fertility (HF) and low fertility (LF) bulls, both in the abundance of SPACA1 at the mRNA, protein, and semen quality levels. Overall, the correlation test results showed a close relationship (P < 0.01) between the abundance of SPACA1 mRNA and protein with field fertility and various semen quality parameters tested in the study. A low level of SPACA1 molecules indicates low fertility and semen quality in Bali bulls. The SPACA1 molecule has the potential to be developed through further research to become a biomarker for determining fertility and semen quality in bulls.

Spatiotemporal functions of leukemia inhibitory factor in embryo attachment and implantation chamber formation

Embryo implantation is crucial for successful pregnancy, requiring appropriate uterine responses to implantation-competent blastocysts. Molecular communication at the maternal-fetal junction governs this process. Leukemia inhibitory factor (Lif) plays a pivotal role in implantation across species. Lif is abundantly expressed in the glandular epithelium during blastocyst-receptive phase and is induced in the stroma surrounding attached blastocysts. While diminished Lif expression leads to infertility, its influence on peri-implantation uteri remains unclear. Therefore, we investigated the role of Lif in uterine physiology using its uterine-specific knockout (uKO) and uterine epithelial-specific KO (eKO) in mice. Lif eKO and uKO mice displayed infertility owing to failed embryo attachment. Recombinant Lif supplementation rescued the reproductive phenotype of Lif eKO mice, but not Lif uKO mice; however, recombinant Lif injection rescued embryo attachment in Lif uKO mice. RNA-seq analysis indicated that Lif governs uterine epithelial genes, but not embryonic genes, to facilitate embryo attachment via activating nuclear Stat3. Concordantly, three-dimensional imaging of the uterine epithelium revealed that luminal closure and crypt formation are regulated by the uterine Lif-Stat3 axis as well as the presence of blastocysts. Collectively, our findings shed light on previously unknown mechanism on how Lif influences uterine functions molecularly and physiologically during early pregnancy.

Exploring the impact of lipid stress on sperm cytoskeleton: insights and prospects

The decline in male fertility correlates with the global rise in obesity and dyslipidaemia, representing significant public health challenges. High-fat diets induce metabolic alterations, including hypercholesterolaemia, hepatic steatosis and atherosclerosis, with detrimental effects on testicular function. Testicular tissue, critically dependent on lipids for steroidogenesis, is particularly vulnerable to these metabolic disruptions. Excessive lipid accumulation within the testes, including cholesterol, triglycerides and specific fatty acids, disrupts essential sperm production processes such as membrane formation, maturation, energy metabolism and cell signalling. This leads to apoptosis, impaired spermatogenesis, and abnormal sperm morphology and function, ultimately compromising male fertility. During spermiogenesis, round spermatids undergo extensive reorganization, including the formation of the acrosome, manchette and specialized filamentous structures, which are essential for defining the final sperm cell shape. In this Perspective, we examine the impact of high-fat diets on the cytoskeleton of spermatogenic cells and its consequences to identify the mechanisms underlying male infertility associated with dyslipidaemia. Understanding these processes may facilitate the development of therapeutic strategies, such as dietary interventions or natural product supplementation, that aim to address infertility in men with obesity and hypercholesterolaemia. The investigation of cytoskeleton response to lipid stress extends beyond male reproduction, offering insights with broader implications.

Deficiency of MFSD6L, an acrosome membrane protein, causes oligoasthenoteratozoospermia in humans and mice

Oligoasthenoteratozoospermia is an important factor affecting male fertility and has been found to be associated with genetic factors. However, there are still a proportion of oligoasthenoteratozoospermia cases that cannot be explained by known pathogenic genetic variants. Here, we perform genetic analyses and identify bi-allelic loss-of-function variants of MFSD6L from an oligoasthenoteratozoospermia-affected family. Mfsd6l knock-out male mice also present male subfertility with reduced sperm concentration, motility, and deformed acrosomes. Further mechanistic analyses reveal that MFSD6L, as an acrosome membrane protein, plays an important role in the formation of acrosome by interacting with the inner acrosomal membrane protein SPACA1. Moreover, poor embryonic development is consistently observed after intracytoplasmic sperm injection treatment using spermatozoa from the MFSD6L-deficient man and male mice. Collectively, our findings reveal that MFSD6L is required for the anchoring of sperm acrosome and head shaping. The deficiency of MFSD6L affects male fertility and causes oligoasthenoteratozoospermia in humans and mice.

Age-dependent variations in proteomic characteristics of spermatozoa in Simmental bull

Increasing the age of bulls results in a decrease in reproductive function, including a reduction in sperm quality, which plays a vital role in determining the fertility of bulls. Through a proteomic approach, this research aims to analyze the influence of age factors on various proteomes contained in bull sperm. Frozen semen samples from Simmental Bulls were categorized into three age groups: two, four, and ≥10 years old. Subsequently, the post-thaw sperm cells obtained were separated based on molecular weight using 1D-SDS-PAGE. Peptides extracted from the bands produced in each age group were subjected to LC-MS/MS analysis. A total of 72 protein types were identified, with 45 being detected in the 4-year-old group and 41 expressed in both the 2 and ≥10-year-old groups. The results provided insights into proteins' role in sperm metabolism across all age groups. Specifically, the 2-year-old group exhibited the expression of proteins associated with acrosome assembly and spermatid development (SPACA1). In contrast, those in the 4-year-old group were linked to motility (PEBP4) and sperm decapacitation factor (PEBP1). Proteins expressed in the 2 and -year-old groups were discovered to be involved in fertilization processes (TEX101). In contrast, the ≥10-year-old age group was associated with hyperactive movement related to capacitation (Tubulin). In conclusion, age influenced the differences observed in the proteomic profile of post-thaw Simmental bull sperm using the 1D-SDS-PAGE tandem LC-MS/MS approach.

Update on the research on the antigens of anti-sperm antibodies over the last decade

This review summarizes the advancements over a decade of research on antigens of anti-sperm antibodies (ASAs), which are key to male immune infertility. Despite the progress in assisted reproductive technologies, understanding the roles and mechanisms of ASAs and their antigens remains vital for immune infertility management. We conducted a comprehensive literature search on PubMed from January 2013 to December 2023 using the following keywords: "anti-sperm antibody," "sperm antigen," and "immune infertility." In this review, we focus on the discoveries in sperm antigen identification and characterization through proteomics, gene disruption technology, and immunoinformatics, along with the development of fertility biomarkers. Here, we discuss the clinical applications of improved ASA detection methods and the progress in the development of immunocontraceptive vaccines. The intersection of advanced diagnostic techniques and vaccine development represents a promising frontier in reproductive health. The findings also highlight the need for standardized ASA detection methods and a comprehensive molecular-level approach to understanding ASA-related infertility. These insights underscore the significance of ongoing reproductive immunology research in enhancing clinical fertility outcomes and contraceptive vaccine development.

Development of functional spermatozoa in mammalian spermiogenesis

Infertility is a global health problem affecting one in six couples, with 50% of cases attributed to male infertility. Spermatozoa are male gametes, specialized cells that can be divided into two parts: the head and the flagellum. The head contains a vesicle called the acrosome that undergoes exocytosis and the flagellum is a motility apparatus that propels the spermatozoa forward and can be divided into two components, axonemes and accessory structures. For spermatozoa to fertilize oocytes, the acrosome and flagellum must be formed correctly. In this Review, we describe comprehensively how functional spermatozoa develop in mammals during spermiogenesis, including the formation of acrosomes, axonemes and accessory structures by focusing on analyses of mouse models.

Characterization of expression patterns and dynamic relocation of Notch proteins during acrosome reaction of bull spermatozoa

Notch is a conserved cell-signaling pathway involved in spermatogenesis regulation. This study firstly evaluated the presence, localization patterns, acquisition origin and relation to acrosome reaction of Notch proteins in bull sperm. Western Blot analysis detected all Notch proteins in ejaculated bull sperm, and immunostaining described their specific sperm localization. Recovery of sperm from different segments showed that Notch proteins have testicular origin (NOTCH1, NOTCH2, DLL4), are sequentially acquired during sperm maturation along epididymal transit (NOTCH3, DLL3, JAGGED1-2), or post-ejaculation (DLL1, NOTCH4). Testis NOTCH2 is ubiquitously expressed in all germ-cell lines, whereas DLL4 is expressed in round and elongated spermatids during the Golgi, Cap, Acrosome and Maturation phases. In vitro spontaneous and induced sperm acrosome reaction induce consistent sperm regional relocation of NOTCH2, DLL4 and JAGGED1, and these relocation patterns are significantly associated to sperm acrosome status. NOTCH2 and JAGGED1 are relocated from the head apical to the post-equatorial regions, whereas DLL4 is lost along with the acrosome, evidencing that sperm spatial redistribution of NOTCH2 and JAGGED1 is linked to acrosome reaction onset, whereas DLL4 loss is linked to AR completion. Overall, results prompt for a relevant Notch role in bull sperm acrosome testicular development, epididymal maturation and acrosome reaction.

Transcriptome Analysis Reveals Spermatogenesis-Related CircRNAs and LncRNAs in Goat Spermatozoa

Mammalian spermatozoa comprises both coding and non-coding RNAs, which are traditionally believed to be a residual of spermatogenesis. The differential expression level of spermatozoal RNAs is also observed between fertile and infertile human, thereby anticipated as potential molecular marker of male fertility. This study investigated the transcriptome profile of goat (Capra hircus) spermatozoa. The sperm transcriptome was analyzed by three different methods viz. RLM-RACE, long-read RNA sequencing (RNAseq) in Nanopore™ platform, and short-read RNAseq in Illumina™ platform. The Illumina™ sequencing discovered 16,604 transcripts with 357 mRNAs having FPKM (fragments per kilobase per million mapped reads) of more than five. The spermatozoal RNA suite included mRNA (94%), rRNA (3%), miscRNA (1%), circRNA (1%), miRNA (1%), etc. This study also predicted circRNAs (127), lncRNAs (655), and imprinted genes (160) that have potential role in male reproduction. The gene ontology analysis revealed the involvement of spermatozoal RNA in regulating male meiosis (TET3, STAT5B), capacitation (ACRBP, CATSPER4), sperm motility (GAS8, TEKT2), spermatogenesis (ADAMTS2, CREB3L4), etc. The spermatozoal RNA were also associated with different biological pathways viz. Wnt signaling pathway, cAMP signaling pathway, AMPK signaling pathway, and MAPK signaling pathways having potential role in spermatogenesis. Overall, this study enlightened the suite of spRNA transcripts in goat and their relevance in male fertility for diagnostic approach.

CCDC28A deficiency causes sperm head defects, reduced sperm motility and male infertility in mice

Mature spermatozoa with normal morphology and motility are essential for male reproduction. The epididymis has an important role in the proper maturation and function of spermatozoa for fertilization. However, factors related to the processes involved in spermatozoa modifications are still unclear. Here we demonstrated that CCDC28A, a member of the CCDC family proteins, is highly expressed in testes and the CCDC28A deletion leads to male infertility. We found CCDC28A deletion had a mild effect on spermatogenesis. And epididymal sperm collected from Ccdc28a-/- mice showed bent sperm heads, acrosomal defects, reduced motility and decreased in vitro fertilization competence whereas their axoneme, outer dense fibers, and fibrous sheath were all normal. Furthermore, we found that CCDC28A interacted with sperm acrosome membrane-associated protein 1 (SPACA1) and glycogen synthase kinase 3a (GSK3A), and deficiencies in both proteins in mice led to bent heads and abnormal acrosomes, respectively. Altogether, our results reveal the essential role of CCDC28A in regulating sperm morphology and motility and suggesting a potential marker for male infertility.

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.

CCDC157 is essential for sperm differentiation and shows oligoasthenoteratozoospermia-related mutations in men

Oligoasthenoteratospermia (OAT), characterized by abnormally low sperm count, poor sperm motility, and abnormally high number of deformed spermatozoa, is an important cause of male infertility. Its genetic basis in many affected individuals remains unknown. Here, we found that CCDC157 variants are associated with OAT. In two cohorts, a 21-bp (g.30768132_30768152del21) and/or 24-bp (g.30772543_30772566del24) deletion of CCDC157 were identified in five sporadic OAT patients, and 2 cases within one pedigree. In a mouse model, loss of Ccdc157 led to male sterility with OAT-like phenotypes. Electron microscopy revealed misstructured acrosome and abnormal head-tail coupling apparatus in the sperm of Ccdc157-null mice. Comparative transcriptome analysis showed that the Ccdc157 mutation alters the expressions of genes involved in cell migration/motility and Golgi components. Abnormal Golgi apparatus and decreased expressions of genes involved in acrosome formation and lipid metabolism were detected in Ccdc157-deprived mouse germ cells. Interestingly, we attempted to treat infertile patients and Ccdc157 mutant mice with a Chinese medicine, Huangjin Zanyu, which improved the fertility in one patient and most mice that carried the heterozygous mutation in CCDC157. Healthy offspring were produced. Our study reveals CCDC157 is essential for sperm maturation and may serve as a marker for diagnosis of OAT.

Deleterious variant in FAM71D cause male infertility with asthenoteratospermia

Asthenoteratospermia is a significant cause of male infertility. FAM71D (Family with sequence similarity 71, member D), as a novel protein exclusively expressed in the testis, has been found to be associated with sperm motility. However, the association of FAM71D mutation with male infertility has yet to be examined. Here, we conducted whole-exome sequencing and identified a homozygous missense mutation c.440G > A (p. Arg147Gln) of FAM71D in an asthenoteratospermia-affected man from a consanguineous family. The FAM71D variant is extremely rare in human population genome databases and predicted to be deleterious by multiple bioinformatics tools. Semen analysis indicated decreased sperm motility and obvious morphological abnormalities in sperm cells from the FAM71D-deficient man. Immunofluorescence assays revealed that the identified FAM71D mutation had an important influence on the assembly of sperm structure-related proteins. Furthermore, intra-cytoplasmic sperm injection (ICSI) treatment performed on the infertile man with FAM71D variant achieved a satisfactory outcome. Overall, our study identified FAM71D as a novel causative gene for male infertility with asthenoteratospermia, for which ICSI treatment may be suggested to acquire good prognosis. All these findings will provide effective guidance for genetic counselling and assisted reproduction treatments of asthenoteratospermia-affected subjects.

Tex46 knockout male mice are sterile secondary to sperm head malformations and failure to penetrate through the zona pellucida

Each year, infertility affects 15% of couples worldwide, with 50% of cases attributed to men. It is assumed that sperm head shape is important for sperm-zona pellucida (ZP) penetration but research has yet to elucidate why. We generated testis expressed 46 (Tex46) knockout mice to investigate the essential roles of TEX46 in mammalian reproduction. We used RT-PCR to demonstrate that Tex46 was expressed exclusively in the male reproductive tract in mice and humans. We created Tex46-/- mice using the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-CRISPR-associated protein 9 (Cas9) system and analyzed their fertility. Tex46 null spermatozoa underwent further evaluation using computer-assisted sperm analysis, light microscopy, and ultrastructural microscopy. We used immunoblot analysis to elucidate relationships between TEX46 and other acrosome biogenesis-related proteins. Mouse and human TEX46 are testis-enriched and encode a transmembrane protein which is conserved from amphibians to mammals. Loss of the mouse TEX46 protein causes male sterility primarily due to abnormal sperm head formation and secondary effects on sperm motility. Tex46 null spermatozoa morphologically lack the typical hooked sperm head appearance and fail to penetrate through the ZP. Electron microscopy of the testicular germ cells reveals malformation of the acrosomal cap, with misshapen sperm head tips and the appearance of a gap between the acrosome head and the nucleus. TEX46 is essential for sperm head formation, sperm penetration through the ZP, and male fertility in mice, and is a putative contraceptive target in men.

A framework for identifying fertility gene targets for mammalian pest control

Fertility-targeted gene drives have been proposed as an ethical genetic approach for managing wild populations of vertebrate pests for public health and conservation benefit. This manuscript introduces a framework to identify and evaluate target gene suitability based on biological gene function, gene expression and results from mouse knockout models. This framework identified 16 genes essential for male fertility and 12 genes important for female fertility that may be feasible targets for mammalian gene drives and other non-drive genetic pest control technology. Further, a comparative genomics analysis demonstrates the conservation of the identified genes across several globally significant invasive mammals. In addition to providing important considerations for identifying candidate genes, our framework and the genes identified in this study may have utility in developing additional pest control tools such as wildlife contraceptives.

WDR38, a novel equatorial segment protein, interacts with the GTPase protein RAB19 and Golgi protein GM130 to play roles in acrosome biogenesis

The WD40-repeat containing (WDR) proteins are enriched in the testis and play important roles in spermatogenesis. In the present study, we investigate the expression profile of WDR38, a novel member of the WDR protein family, in humans and mice. RT-qPCR (reverse transcription-quantitative polymerase chain reaction) results demonstrate that WDR38 mRNA is abundantly expressed in both the human and mouse testis. The expression of mouse Wdr38 is strictly regulated during development. Further immunofluorescence staining results show that WDR38 is located in the equatorial segment of the acrosome in human and mouse mature spermatozoa and is involved in acrosome biogenesis. Subcellular localization analysis reveals that the mouse Wdr38 protein is distributed in the perinuclear cytoplasm of transfected cells and colocalizes with the GTPase protein Rab19 and Golgi protein GM130. Coimmunoprecipitation (co-IP) assays demonstrate that Wdr38, Rab19 and GM130 interact with each other in the mouse testis and in HEK293T cells. In acrosome biogenesis, Wdr38, Rab19 and GM130 aggregate at the nuclear membrane to form large vesicles, and GM130 then detaches and moves towards the caudal region of the nucleus, whereas the Wdr38/Rab19 complex spreads along the dorsal nuclear edge and finally docks to the equatorial segment. These results indicate that WDR38 is a novel equatorial segment protein that interacts with the GTPase protein RAB19 and Golgi protein GM130 to play roles in acrosome biogenesis.

Kinesin-14 KIFC1 promotes acrosome formation and chromatin maturation during mouse spermiogenesis

KIFC1, a member of kinesin-14 subfamily motors, is essential for meiotic cell division and acrosome formation during spermatogenesis. However, the functions of KIFC1 in the formation and maintenance of the acrosome in male germ cells remain to be elucidated. In this study, we report the structural deformities of acrosomes in the in vivo KIFC1 inhibition mouse models. The proacrosomal vesicles diffuse into the cytoplasm and form atypical acrosomal granules. This phenotype is consistent with globozoospermia patients and probably results from the failure of the Golgi-derived vesicle trafficking and actin filament organization. Moreover, the multinucleated and undifferentiated spermatogenic cells in the epidydimal lumen after KIFC1 inhibition reveal the specific roles of KIFC1 in regulating post-meiotic maturation. Overall, our results uncover KIFC1 as an essential regulator in the trafficking, fusion and maturation of acrosomal vesicles during spermiogenesis.

Inceptor facilitates acrosomal vesicle formation in spermatids and is required for male fertility

Spermatogenesis is a crucial biological process that enables the production of functional sperm, allowing for successful reproduction. Proper germ cell differentiation and maturation require tight regulation of hormonal signals, cellular signaling pathways, and cell biological processes. The acrosome is a lysosome-related organelle at the anterior of the sperm head that contains enzymes and receptors essential for egg-sperm recognition and fusion. Even though several factors crucial for acrosome biogenesis have been discovered, the precise molecular mechanism of pro-acrosomal vesicle formation and fusion is not yet known. In this study, we investigated the role of the insulin inhibitory receptor (inceptor) in acrosome formation. Inceptor is a single-pass transmembrane protein with similarities to mannose-6-phosphate receptors (M6PR). Inceptor knockout male mice are infertile due to malformations in the acrosome and defects in the nuclear shape of spermatozoa. We show that inceptor is expressed in early spermatids and mainly localizes to vesicles between the Golgi apparatus and acrosome. Here we show that inceptor is an essential factor in the intracellular transport of trans-Golgi network-derived vesicles which deliver acrosomal cargo in maturing spermatids. The absence of inceptor results in vesicle-fusion defects, acrosomal malformation, and male infertility. These findings support our hypothesis of inceptor as a universal lysosomal or lysosome-related organelle sorting receptor expressed in several secretory tissues.

PDCL2 is essential for sperm acrosome formation and male fertility in mice

BACKGROUND

Each year, infertility affects 15% of couples worldwide, with 50% of cases attributed to men. Globozoospermia is an uncommon cause of male factor infertility, characterized by defects in sperm acrosome formation, leading to round-headed spermatozoa.

OBJECTIVE

We generated Pdcl2 knockout mice to investigate the essential roles of PDCL2 in mammalian reproduction.

MATERIALS AND METHODS

We used reverse transcription-polymerase chain reaction to demonstrate that PDCL2 was expressed exclusively in the male reproductive tract in mice and humans. We created Pdcl2 knockout mice using the CRISPR-Cas9 system and analyzed their fertility. Pdcl2 null spermatozoa underwent further evaluation using computer-assisted sperm analysis, light microscopy, and ultrastructural microscopy. We used immunoblot analysis and immunofluorescence to elucidate relationships between PDCL2 and other acrosomal proteins.

RESULTS

The PDC family is highly conserved in eukaryotes. Mouse and human PDCL2 are testis enriched and localized to the testicular endoplasmic reticulum. Loss of the protein causes sterility because of abnormal acrosome biogenesis during spermiogenesis and immotility. Furthermore, Pdcl2 null spermatozoa have rounded heads, similar to globozoospermia in humans. Observation of the knockout testis shows a lack of acrosomal cap formation, aberrant localization of mitochondria in the sperm head, and misshapen nuclei.

CONCLUSION

PDCL2 is essential for sperm acrosome development and male fertility in mice and is a putative contraceptive target in men.

Testis-specific proteins, TSNAXIP1 and 1700010I14RIK, are important for sperm motility and male fertility in mice

BACKGROUND

TSN (translin), also called testis brain RNA-binding protein, binds to TSNAX (translin-associated factor X) and is suggested to play diverse roles, such as RNA metabolism and DNA damage response. TSNAXIP1 (Translin-associated factor X-interacting protein 1) was identified as a TSNAX-interacting protein using a yeast two-hybrid system, but its function in vivo was unknown.

OBJECTIVE

To reveal the function of TSNAXIP1 in vivo in mice.

MATERIALS AND METHODS

We generated Tsnaxip1 knockout mice using the CRISPR/Cas9 system and analyzed their fertility and sperm motility. Further, we generated 1700010I14Rik knockout mice, because 1700010I14RIK is also predominantly expressed in testes and contains the same Pfam (protein families) domain as TSNAXIP1.

RESULTS

Reduced male fertility and impaired sperm motility with asymmetric flagellar waveforms were observed in not only Tsnaxip1 but also 1700010I14Rik knockout mice. Unlike Tsn knockout mice, no abnormalities were found in testicular sections of either Tsnaxip1 or 1700010I14Rik knockout mice. Furthermore, TSNAXIP1 was detected in the sperm tail and fractionated with axonemal proteins.

DISCUSSION AND CONCLUSION

Unlike the TSN-TSNAX complex, whose disruption causes abnormal vacuoles in mouse testes, TSNAXIP1 and 1700010I14RIK may play roles in regulating sperm flagellar beating patterns.

Spermatogenic cell-specific SPACA4 is essential for efficient sperm-zona pellucida binding in vitro

Fertilization is a complex and highly regulated process that involves a series of molecular interactions between sperm and oocytes. However, the mechanisms of proteins involved in human fertilization, such as that of testis-specific SPACA4, remain poorly understood. Here we demonstrated that SPACA4 is a spermatogenic cell-specific protein. SPACA4 is expressed during spermatogenesis, upregulated in early-stage spermatids, and downregulated in elongating spermatids. SPACA4 is an intracellular protein that locates in the acrosome and is lost during the acrosome reaction. Incubation with antibodies against SPACA4 inhibited the binding of spermatozoa to zona pellucida. SPACA4 protein expression levels across different semen parameters were similar but varied significantly among patients. A prospective clinical study found no association between SPACA4 protein levels and fertilization or cleavage rates. Thus, the study suggests a novel function for SPACA4 in human fertilization in a non-dose-dependent manner. However, a larger clinical trial is required to evaluate the potential use of sperm SPACA4 protein levels to predict fertilization potential.

A framework for identifying fertility gene targets for mammalian pest control

Fertility-targeted gene drives have been proposed as an ethical genetic approach for managing wild populations of vertebrate pests for public health and conservation benefit.This manuscript introduces a framework to identify and evaluate target gene suitability based on biological gene function, gene expression, and results from mouse knockout models.This framework identified 16 genes essential for male fertility and 12 genes important for female fertility that may be feasible targets for mammalian gene drives and other non-drive genetic pest control technology. Further, a comparative genomics analysis demonstrates the conservation of the identified genes across several globally significant invasive mammals.In addition to providing important considerations for identifying candidate genes, our framework and the genes identified in this study may have utility in developing additional pest control tools such as wildlife contraceptives.

Mapping the human sperm proteome - novel insights into reproductive research

INTRODUCTION

Spermatozoa are highly specialized cells with unique morphology. In addition, spermatozoa lose a considerable amount of cytoplasm during spermiogenesis, when they also compact their DNA, resulting in a transcriptionally quiescent cell. Throughout the male reproductive tract, sperm will acquire proteins that enable them to interact with the female reproductive tract. After ejaculation, proteins undergo post-translational modifications for sperm to capacitate, hyperactivate and fertilize the oocyte. Many proteins have been identified as predictors of male infertility, and also investigated in diseases that compromise reproductive potential.

AREAS COVERED

In this review we proposed to summarize the recent findings about the sperm proteome and how they affect sperm structure, function, and fertility. A literature search was performed using PubMed and Google Scholar databases within the past 5 years until August 2022.

EXPERT OPINION

Sperm function depends on protein abundance, conformation, and PTMs; understanding the sperm proteome may help to identify pathways essential to fertility, even making it possible to unravel the mechanisms involved in idiopathic infertility. In addition, proteomics evaluation offers knowledge regarding alterations that compromise the male reproductive potential.

Review: Evaluation of bull fertility. Functional and molecular approaches

With the term "assisted reproduction technologies" in modern cattle farming, one could imply the collection of techniques that aim at the optimal use of bovine gametes to produce animals of high genetic value in a time- and cost-efficient manner. The accurate characterisation of sperm quality plays a critical role for the efficiency of several assisted reproduction-related procedures, such as sperm processing, in vitro embryo production and artificial insemination. Bull fertility is ultimately a collective projection of the ability of a series of ejaculates to endure sperm processing stress, and achieve fertilisation of the oocyte and production of a viable and well-developing embryo. In this concept, the assessment of sperm functional and molecular characteristics is key to bull fertility diagnostics and prognostics. Among others, functional features linked to sperm plasma membrane, acrosome and DNA integrity are usually assessed as a measure of the ability of sperm to express the phenotypes that will allow them to maintain their homeostasis and orchestrate-in a strict temporal manner-the course of events that will enable the delivery of their genetic content to the oocyte upon fertilisation. Nevertheless, measures of sperm functionality are not always adequate indicators of bull fertility. Nowadays, advancements in the field of molecular biology have facilitated the profiling of several biomolecules in male gametes. The molecular profiling of bovine sperm offers a deeper insight into the mechanisms underlying sperm physiology and, thus, can reveal novel candidate markers for bull fertility prognosis. In this review, the importance of three organelles (the nucleus, the plasma membrane and the acrosome) for the characterisation of sperm fertilising capacity and bull fertility is discussed at functional and molecular levels. In particular, information about sperm head morphometry, chromatin structure, viability as well as the ability of sperm to capacitate and undergo the acrosome reaction are presented in relation to the cryotolerance of male gametes and bull fertility. Finally, major spermatozoal coding and non-coding RNAs, and proteins that are involved in the above-mentioned aspects of sperm functionality are also summarised.

The interplay of arsenic, silymarin, and NF-ĸB pathway in male reproductive toxicity: A review

Arsenic toxicity is one of the most trending reasons for several malfunctions, particularly reproductive toxicity. The exact mechanism of arsenic poisoning is a big question mark. Exposure to arsenic reduces sperm count, impairs fertilization, and causes inflammation and genotoxicity through interfering with autophagy, epigenetics, ROS generation, downregulation of essential protein expression, metabolite changes, and hampering several signaling cascades, particularly by the alteration of NF-ĸB pathway. This work tries to give a clear idea about the different aspects of arsenic resulting in male reproductive complications, often leading to infertility. The first part of this article explains the implications of arsenic poisoning and the crosstalk of the NF-ĸB pathway in male reproductive toxicity. Silymarin is a bioactive compound that exerts anti-cancer and anti-inflammatory properties and has demonstrated hopeful outcomes in several cancers, including colon cancer, breast cancer, and skin cancer, by downregulating the hyperactive NF-ĸB pathway. The next half of this article thus sheds light on silymarin's therapeutic potential in inhibiting the NF-ĸB signaling cascade, thus offering protection against arsenic-induced male reproductive toxicity.

Human globozoospermia-related genes and their role in acrosome biogenesis

The mammalian acrosome is a secretory vesicle attached to the sperm nucleus whose fusion with the overlying plasma membrane is required to achieve fertilization. Acrosome biogenesis starts during meiosis, but it lasts through the entire process of haploid cell differentiation (spermiogenesis). Acrosome biogenesis is a stepwise process that involves membrane traffic from the Golgi apparatus, but it also seems that the lysosome/endosome system participates in this process. Defective sperm head morphology is accompanied by defective acrosome shape and function, and patients with these characteristics are infertile or subfertile. The most extreme case of acrosome biogenesis failure is globozoospermia syndrome, which is primarily characterized by the presence of round-headed spermatozoa without acrosomes with cytoskeleton defects around the nucleus and infertility. Several genes participating in acrosome biogenesis have been uncovered using genetic deletions in mice, but only a few of them have been found to be deleted or modified in patients with globozoospermia. Understanding acrosome biogenesis is crucial to uncovering the molecular basis of male infertility and developing new diagnostic tools and assisted reproductive technologies that may help infertile patients through more effective treatment techniques. This article is categorized under: Reproductive System Diseases > Environmental Factors Infectious Diseases > Stem Cells and Development Reproductive System Diseases > Molecular and Cellular Physiology.

Characterization of SPINK2, SPACA7 and PDCL2: Effect of immunization on fecundity, sperm function and testicular transcriptome

Testicular factors play a vital role in spermatogenesis. We characterized the functional role of rat Spink2, Spaca7 and Pdcl2 genes. Their primary, secondary and tertiary structure were deduced in silico. The genes of rat Spink2, Spaca7 and Pdcl2 mRNA were predominantly expressed in the testis. SPINK2, SPACA7 and PDCL2 protein expression was evident in all the cell types of testis and on spermatozoa. Ablation of each of these proteins by active immunization resulted in reduced fecundity and sperm count. Damage to the anatomical architecture of testis and epididymis was evident. In SPINK2 immunized rats, 283 genes were differentially regulated while it was 434 and 872 genes for SPACA7 and PDCL2 respectively. Genes that were differentially regulated in the testis of SPINK2 immunized rats primarily belonged to extracellular exosome formation, extracellular space and response to drugs. SPACA7 ablation affected genes related to extracellular space, oxidation-reduction processes, endoplasmic reticulum membrane and response to drugs. Differential gene expression was observed for nuclear function, protein binding and positive regulation of transcription from RNA polymerase II promoter in testis of PDCL2 immunized rats. Results of our study demonstrate the role of SPINK2, SPACA7 and PDCL2 in spermatogenesis and in important molecular processes that may dictate testicular function and other physiological responses as well.

Single-Cell Transcriptomic Profiling of the Mouse Testicular Germ Cells Reveals Important Role of Phosphorylated GRTH/DDX25 in Round Spermatid Differentiation and Acrosome Biogenesis during Spermiogenesis

Gonadotropin-regulated testicular RNA helicase (GRTH)/DDX25 is a member of DEAD-box family of RNA helicase essential for the completion of spermatogenesis and male fertility, as evident from GRTH-knockout (KO) mice. In germ cells of male mice, there are two species of GRTH, a 56 kDa non-phosphorylated form and 61 kDa phosphorylated form (pGRTH). GRTH Knock-In (KI) mice with R242H mutation abolished pGRTH and its absence leads to infertility. To understand the role of the GRTH in germ cell development at different stages during spermatogenesis, we performed single-cell RNA-seq analysis of testicular cells from adult WT, KO and KI mice and studied the dynamic changes in gene expression. Pseudotime analysis revealed a continuous developmental trajectory of germ cells from spermatogonia to elongated spermatids in WT mice, while in both KO and KI mice the trajectory was halted at round spermatid stage indicating incomplete spermatogenesis process. The transcriptional profiles of KO and KI mice were significantly altered during round spermatid development. Genes involved in spermatid differentiation, translation process and acrosome vesicle formation were significantly downregulated in the round spermatids of KO and KI mice. Ultrastructure of round spermatids of KO and KI mice revealed several abnormalities in acrosome formation that includes failure of pro-acrosome vesicles to fuse to form a single acrosome vesicle, and fragmentation of acrosome structure. Our findings highlight the crucial role of pGRTH in differentiation of round spermatids into elongated spermatids, acrosome biogenesis and its structural integrity.

1α,25-dihydroxyvitamin D3 supplementation alleviates perfluorooctanesulfonate acid-induced reproductive injury in male mice: Modulation of Nrf2 mediated oxidative stress response

Perfluorooctanesulfonate acid (PFOS) is a typical persistent organic pollutant that widely exists in the environment. To clarify the toxic effects and mechanisms of PFOS and to find effective intervention strategies have been attracted global attention. Here, we investigated the effects of PFOS on the male reproductive system and explored the potential protective role of 1α,25-dihydroxyvitamin D₃ (1α,25(OH)₂ D₃ ). Our results showed that 1α,25(OH)₂ D₃ intervention significantly improved PFOS-induced sperm quality decline and testicular damage. Moreover, 1α,25(OH)₂ D₃ aggrandized the total antioxidant capacity. Furthermore, after PFOS exposure, the transcription factor nuclear factor erythroid-related factor 2 (Nrf2) was adaptively increased together with its target genes, such as HO-1, NQO1, and SOD2. Meanwhile, 1α,25(OH)₂ D₃ ameliorated PFOS-induced augment of Nrf2 and target genes. These findings indicated that 1α,25(OH)₂ D₃ might attenuate PFOS-induced reproductive injury in male mice via Nrf2-mediated oxidative stress.

Comparative proteomic analysis of seminal plasma exosomes in buffalo with high and low sperm motility

BACKGROUND

Exosomes are nanosized membranous vesicles secreted by various types of cells, which facilitate intercellular communication by transporting bioactive compounds. Exosomes are abundant in biological fluids including semen, and their protein composition and the potential of seminal plasma exosomes (SPEs) as fertility biomarkers were elucidated in humans, however, little information is available regarding buffalo (Bubalus bubalis). Here, we examined protein correlation between spermatozoa, seminal plasma (SP), and SPEs, and we compared and analyzed protein differences between high-motility (H-motility) and low-motility (L-motility) SPEs in buffalo.

RESULTS

SPEs were concentrated and purified by ultracentrifugation combined with sucrose density gradient centrifugation, followed by verification using western blotting, nanoparticle tracking analysis, and transmission electron microscopy. Protein composition in spermatozoa, SP and SPEs, and protein difference in H- and L-motility SPEs were identified by LC-MS/MS proteomic analysis and were functionally analyzed through comprehensive bioinformatics. Many SPEs proteins originated from spermatozoa and SP, and nearly one third were also present in spermatozoa and SP. A series of proteins associated with reproductive processes including sperm capacitation, spermatid differentiation, fertilization, sperm-egg recognition, membrane fusion, and acrosome reaction were integrated in a functional network. Comparative proteomic analyses showed 119 down-regulated and 41 up-regulated proteins in L-motility SPEs, compared with H-motility SPEs. Gene Ontology (GO) enrichment of differentially expressed proteins (DEPs) showed that most differential proteins were located in sperm and vesicles, with activities of hydrolase and metalloproteinase, and were involved in sperm-egg recognition, fertilization, single fertilization, and sperm-zona pellucida binding processes, etc. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that differential proteins were mainly involved in the PPRP signaling pathway, calcium signaling pathway, and cAMP signaling pathway, among others. Furthermore, 6 proteins associated with reproduction were validated by parallel reaction monitoring analysis.

CONCLUSION

This study provides a comprehensive description of the seminal plasma exosome proteome and may be of use for further screening of biomarkers associated with male infertility.

Identification of protein candidates in spermatozoa of water buffalo (Bubalus bubalis) bulls helps in predicting their fertility status

The water buffalo (Bubalus bubalis) is an indispensable part of the Indian dairy sector and in several instances, the farmers incur economic losses due to failed pregnancy after artificial insemination (AI). One of the key factors for the failure of conception is the use of semen from the bulls of low fertilizing potential and hence, it becomes important to predict the fertility status before performing AI. In this study, the global proteomic profile of high fertile (HF) and low fertile (LF) buffalo bull spermatozoa was established using a high-throughput LC-MS/MS technique. A total of 1,385 proteins (≥1 high-quality PSM/s, ≥1 unique peptides, p < 0.05, FDR < 0.01) were identified out of which, 1,002 were common between both the HF and LF groups while 288 and 95 proteins were unique to HF and LF groups respectively. We observed 211 and 342 proteins were significantly high (log Fc ≥ 2) and low abundant (log Fc ≤ 0.5) in HF spermatozoa (p < 0.05). Gene ontology analysis revealed that the fertility associated high abundant proteins in HF were involved in spermatogenesis, sperm motility, acrosome integrity, zona pellucida binding and other associated sperm functions. Besides this, the low abundant proteins in HF were involved in glycolysis, fatty acid degradation and inflammation. Furthermore, fertility related differentially abundant proteins (DAPs) on sperm viz., AKAP3, Sp17, and DLD were validated through Western blotting and immunocytochemistry which was in coherence with the LC-MS/MS data. The DAPs identified in this study may be used as potential protein candidates for predicting fertility in buffaloes. Our findings provide an opportunity in mitigating the economic losses that farmers incur due to male infertility.

Phthalate plasticizer decreases the prion-like protein doppel essential for structural integrity and function of spermatozoa

Di-n-butyl phthalate (DBP), a well-known endocrine disruptor, causes male reproductive dysfunction. To understand the underlying mechanisms, we performed histological, endocrinological, and biochemical analyses and assessed the expression of genes involved in spermatogenesis and sperm function according to OECD test guideline 407. Following 28 days of administration of the lowest observed adverse effect level dose of DBP to mice, no significant changes in body weight, testis and epididymis weights and histology, serum testosterone level, or testicular daily sperm production were found. Nonetheless, the motility of the epididymal sperm of the DBP group was significantly decreased together with an increase in the incidence of bent tails and abnormal heads. In the testes of the DBP group, lipid peroxidation (LPO) level was significantly increased and testicular Bcl-2 mRNA level was significantly decreased together with an increase in the Bax/Bcl-2 mRNA ratio. In the testes of the DBP group, levels of Prnd mRNA and protein and Pou4f1 mRNA, an activator of the Prnd promotor, were significantly decreased. Of note, prion-like protein doppel (PRND) was significantly decreased together with decreased PRND immunoreactivity in the head, midpiece, and tail of sperm. In the testes of the DBP group, levels of Sox9, Sgp1, and Sgp2 mRNA, which are functional Sertoli cell markers, were significantly decreased. Level of Amh mRNA, a Sertoli cell immaturity marker, was significantly increased together with that of Inha mRNA, suggesting deregulation of the brain-gonadal axis. Together, our findings suggest that DBP at present dosage may potentiate LPO generation and Sertoli cell immaturity via downregulation of Sox9 and disruption of the Pou4f1-Prnd gene network in post-meiotic germ cells without visible changes in spermatogenesis or testosterone level. This may result in structural and functional abnormalities in spermatozoa. Additionally, our findings suggest that assessment of the male reproductive toxicity of phthalate ester plasticizers based on conventional OECD test guidelines should be reconsidered.

IRGC1, a testis-enriched immunity related GTPase, is important for fibrous sheath integrity and sperm motility in mice

Immunity-related GTPases (IRGs), also known as p47 GTPases, are a family of interferon-inducible proteins that play roles in immunity defense against intracellular pathogens. Although the molecular functions of IRGs have been well studied, the function of the family member, IRGC1, remains unclear. IRGC1 is unique among IRGs because its expression is not induced by interferon and it is expressed predominantly in the testis. Further, IRGC1 is well conserved in mammals unlike other IRGs. Here, we knocked out (KO) Irgc1 in mice using the CRISPR/Cas9 system and found that the fertility of Irgc1 KO males was severely impaired because of abnormal sperm motility. Further analyses with a transmission electron microscope revealed that the fibrous sheath (FS), an accessory structure of the sperm tail, was disorganized in Irgc1 KO mice. In addition, IRGC1 was detected in the sperm tail and fractionated with FS proteins. These results suggest that IRGC1 is a component of the FS and is involved in the correct formation of the FS.

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.

Sperm chromatin condensation: epigenetic mechanisms to compact the genome and spatiotemporal regulation from inside and outside the nucleus

Sperm chromatin condensation is a critical step in mammalian spermatogenesis to protect the paternal DNA from external damaging factors and to acquire fertility. During chromatin condensation, various events proceed in a chronological order, independently or in sequence, interacting with each other both inside and outside the nucleus to support the dramatic chromatin changes. Among these events, histone-protamine replacement, which is concomitant with acrosome biogenesis and cytoskeletal alteration, is the most critical step associated with nuclear elongation. Failures of not only intranuclear events but also extra-nuclear events severely affect sperm shape and chromatin state and are subsequently linked to infertility. This review focuses on nuclear and non-nuclear factors that affect sperm chromatin condensation and its effects, and further discusses the possible utility of sperm chromatin for clinical applications.

Awareness and reporting of globozoospermia among in vitro fertilization and andrology laboratories: A national survey

Globozoospermia (GZ) is a rare disorder found in less than 0.1% of infertile men in which spermatozoa lack acrosomes necessary for penetration of an oocyte. While methods have been demonstrated to allow globozoospermic men to achieve a viable pregnancy with their partner, the Wold Health Organization considers identifying and reporting GZ on semen analysis to be 'important'. Our study aims to determine if and to what extent in vitro fertilization (IVF) laboratories nationwide recognize and report GZ on semen analysis reports. We constructed an IRB-approved survey sent nationwide to IVF and andrology clinic laboratory directors listed by the Society for Assisted Reproductive Technology and/or the American Society for Reproductive Medicine. Results from the survey were de-identified for analysis. A total of 490 surveys were sent with a response rate of 10% (n = 51). Most respondents (66%) practiced in a private, rather than academic, setting. A majority of respondents were confident in their technicians' knowledge of GZ (86%) and ability to identify it on a sample (94%). However, only half of respondents noted a space to report the concern for GZ to the ordering physician, and 25% of respondents did not feel their clinic was able to identify patients where there is a concern for GZ. Similarly, 84% of respondents did not report a percent of acrosome-deficient sperm. Less than half of respondents reported that their clinic has previously diagnosed GZ. Though the majority of respondents felt that their laboratory technicians would be able to identify GZ, a significant minority felt that their clinic did not have means to be able to report concern for GZ. This may be due to the absence of a proper channel to report a concern for GZ, a lack of knowledge about the condition, or failure to distinguish GZ from a broader reported percentage of morphologically abnormal sperm. Given evidence that the diagnosis of GZ may be under-reported in the United States, there should be a national standard for laboratory technicians to be trained to recognize GZ and be able to report their suspicion to the ordering clinician.

Repression of autophagy leads to acrosome biogenesis disruption caused by a sub-chronic oral administration of polystyrene nanoparticles

As a new widespread contaminant, nanoplastics (NPs) pose a potential risk to human health. Nevertheless, the adverse effects of NPs on the male reproductive system are poorly understood. In this study, we aimed to determine the effects of polystyrene nanoplastics (PS-NPs) (50 nm) on sperm quality, with a focus on the acrosome defects. After 35 days of intragastric administration, sperm quality was decreased and testicular structures were impaired in mice exposed to PS-NPs in both the medium (1.0 mg/kg) and high dose (10 mg/kg) groups. No significant changes were observed in the low dose (0.2 mg/kg) group. Meanwhile, acrosome parameters including acrosome integrity and acrosome reaction were decreased after the administration of PS-NPs. These findings were consistent with the disruption of acrosome biogenesis, as identified by the changed testicular ultrastructure. Additionally, the findings were further validated using seven marker genes (Gba2, Pick1, Gopc, Hrb, Zpbp1, Spaca1 and Dpy19l2) essential for acrosome formation, which showed that two of these genes (Gopc and Dpy19l2) were significantly down-regulated. Moreover, repressed autophagy was observed in the testes of PS-NPs-exposed mice based on autophagy-related protein expression. This phenomenon was further verified in GC-2spd cells treated with PS-NPs (50 μg/mL, 100 μg/mL, 200 μg/mL for 24 h). The potential role of autophagy in such acrosome defects was explored by using the autophagy inhibitor 3-methyladenine (3-MA), autophagy activator rapamycin or beclin-1 siRNA. The results showed that Golgi-associated vesicle disorganization was exacerbated with the 3-MA and beclin-1 siRNA pretreatments, but decreased with the rapamycin pretreatment, and the expression of GOPC and DPY19L2 was also altered. These results indicated that autophagy might be involved in the PS-NPs-induced acrosome lesions based on the regulation of two key acrosome-formation proteins, GOPC and DPY19L2. Altogether, our results will provide new insights into the PS-NPs-induced male reproductive impairment.

Exploring the ovine sperm transcriptome by RNAseq techniques. I Effect of seasonal conditions on transcripts abundance

Understanding the cell molecular changes occurring as a results of climatic circumstances is crucial in the current days in which climate change and global warming are one of the most serious challenges that living organisms have to face. Sperm are one of the mammals’ cells most sensitive to heat, therefore evaluating the impact of seasonal changes in terms of its transcriptional activity can contribute to elucidate how these cells cope with heat stress events. We sequenced the total sperm RNA from 64 ejaculates, 28 collected in summer and 36 collected in autumn, from 40 Manchega rams. A highly rich transcriptome (11,896 different transcripts) with 90 protein coding genes that exceed an average number of 5000 counts were found. Comparing transcriptome in the summer and autumn ejaculates, 236 significant differential abundance genes were assessed, most of them (228) downregulated. The main functions that these genes are related to sexual reproduction and negative regulation of protein metabolic processes and kinase activity. Sperm response to heat stress supposes a drastic decrease of the transcriptional activity, and the upregulation of only a few genes related with the basic functions to maintain the organisms’ homeostasis and surviving. Rams’ spermatozoids carry remnant mRNAs which are retrospectively indicators of events occurring along the spermatogenesis process, including abiotic factors such as environmental temperature.

Molecular basis of the morphogenesis of sperm head and tail in mice

Background

The spermatozoon has a complex molecular apparatus necessary for fertilization in its head and flagellum. Recently, numerous genes that are needed to construct the molecular apparatus of spermatozoa have been identified through the analysis of genetically modified mice.

Methods

Based on the literature information, the molecular basis of the morphogenesis of sperm heads and flagella in mice was summarized.

Main findings (Results)

The molecular mechanisms of vesicular trafficking and intraflagellar transport in acrosome and flagellum formation were listed. With the development of cryo‐electron tomography and mass spectrometry techniques, the details of the axonemal structure are becoming clearer. The fine structure and the proteins needed to form the central apparatus, outer and inner dynein arms, nexin‐dynein regulatory complex, and radial spokes were described. The important components of the formation of the mitochondrial sheath, fibrous sheath, outer dense fiber, and the annulus were also described. The similarities and differences between sperm flagella and Chlamydomonas flagella/somatic cell cilia were also discussed.

Conclusion

The molecular mechanism of formation of the sperm head and flagellum has been clarified using the mouse as a model. These studies will help to better understand the diversity of sperm morphology and the causes of male infertility.

Proteomic fertility markers in ram sperm

Precise estimation of ram fertility is important for sheep farming to sustain reproduction efficiency and profitability of production. There, however, is no conventional method to accurately predict ram fertility. The objective of this study, therefore, was to ascertain proteomic profiles of ram sperm having contrasting fertility phenotypes. Mature rams (n = 66) having greater pregnancy rates than average (89.4 ± 7.2%) were assigned into relatively-greater fertility (GF; n = 31; 94.5 ± 2.8%) whereas those with less-than-average pregnancy rates were assigned into a lesser-fertility (LF; n = 25; 83.1 ± 5.73%; P = 0.028) group. Sperm samples from the outlier greatest- and least-fertility rams (n = 6, pregnancy rate; 98.4 ± 1.8% and 76.1 ± 3.9%) were used for proteomics assessments utilizing Label-free LC-MS/MS. A total of 997 proteins were identified, and among these, 840 were shared by both groups, and 57 and 93 were unique to GF and LF, respectively. Furthermore, 190 differentially abundant proteins were identified; the abundance of 124 was larger in GF while 66 was larger in LF rams. The GF ram sperm had 79 GO/pathway terms in ten major biological networks while there were 47 GO/pathway terms in six biological networks in sperm of LF rams. Accordingly, differential abundances of sperm proteins between sperm of GF and LF rams were indicative of functional implications of sperm proteome on male fertility. The results of this study emphasize there are potential protein markers for evaluation of semen quality and estimation of ram sperm fertilizing capacity.

FAM209 associates with DPY19L2, and is required for sperm acrosome biogenesis and fertility in mice

Infertility afflicts up to 15% of couples globally each year with men a contributing factor in 50% of these cases. Globozoospermia is a rare condition found in infertile men, which is characterized by defective acrosome biogenesis leading to the production of round-headed sperm. Here, we report that family with sequence similarity 209 (Fam209) is required for acrosome biogenesis in mouse sperm. FAM209 is a small transmembrane protein conserved among mammals. Loss of Fam209 results in fertility defects that are secondary to abnormalities in acrosome biogenesis during spermiogenesis, reminiscent of globozoospermia. Analysis of the FAM209 proteome identified DPY19L2, whose human orthologue is involved in the majority of globozoospermia cases. Although mutations in human and mouse Dpy19l2 have been shown to cause globozoospermia, no in vivo interacting partners of DPY19L2 have been identified until now. FAM209 colocalizes with DPY19L2 at the inner nuclear membrane to maintain the developing acrosome. Here, we identified FAM209 as the first interacting partner of DPY19L2, and the second protein that is essential for acrosome biogenesis that localizes to the inner nuclear membrane.

DNA methylation changes induced by BDE-209 are related to DNA damage response and germ cell development in GC-2spd

Decabrominated diphenyl ether (BDE-209) is generally utilized in multiple polymer materials as common brominated flame retardant. BDE-209 has been listed as persistent organic pollutants (POPs), which was considered to be reproductive toxin in the environment. But it still remains unclear about the effects of BDE-209 on DNA methylation and the induced-male reproductive toxicity. Due to the extensive epigenetic regulation in germ line development, we hypothesize that BDE-209 exposure impacts the statue of DNA methylation in spermatocytes in vitro. Therefore, the mouse GC-2spd (GC-2) cells were used for the genome wide DNA methylation analysis after treated with 32 μg/mL BDE-209 for 24 hr. The results showed that BDE-209 caused genomic methylation changes with 32,083 differentially methylated CpGs in GC-2 cells, including 16,164 (50.38%) hypermethylated and 15,919 (49.62%) hypomethylated sites. With integrated analysis of DNA methylation data and functional enrichment, we found that BDE-209 might affect the functional transcription in cell growth and sperm development by differential gene methylation. qRT-PCR validation demonstrated the involvement of p53-dependent DNA damage response in the GC-2 cells after BDE-209 exposure. In general, our findings indicated that BDE-209-induced genome wide methylation changes could be interrelated with reproductive dysfunction. This study might provide new insights into the mechanisms of male reproductive toxicity under the environmental exposure to BDE-209.

FAM71F1 binds to RAB2A and RAB2B and is essential for acrosome formation and male fertility in mice

The acrosome is a cap-shaped, Golgi-derived membranous organelle that is located over the anterior of the sperm nucleus and highly conserved throughout evolution. Although morphological changes during acrosome biogenesis in spermatogenesis have been well described, the molecular mechanism underlying this process is still largely unknown. Family with sequence similarity 71, member F1 and F2 (FAM71F1 and FAM71F2) are testis-enriched proteins that contain a RAB2B-binding domain, a small GTPase involved in vesicle transport and membrane trafficking. Here, by generating mutant mice for each gene, we found that Fam71f1 is essential for male fertility. In Fam71f1-mutant mice, the acrosome was abnormally expanded at the round spermatid stage, likely because of enhanced vesicle trafficking. Mass spectrometry analysis after immunoprecipitation indicated that, in testes, FAM71F1 binds not only RAB2B, but also RAB2A. Further study suggested that FAM71F1 binds to the GTP-bound active form of RAB2A/B, but not the inactive form. These results indicate that a complex of FAM71F1 and active RAB2A/B suppresses excessive vesicle trafficking during acrosome formation.

Uterine Epithelial LIF Receptors Contribute to Implantation Chamber Formation in Blastocyst Attachment

Recent studies have demonstrated that the formation of an implantation chamber composed of a uterine crypt, an implantation-competent blastocyst, and uterine glands is a critical step in blastocyst implantation in mice. Leukemia inhibitory factor (LIF) activates signal transducer and activator of transcription 3 (STAT3) precursors via uterine LIF receptors (LIFRs), allowing successful blastocyst implantation. Our recent study revealed that the role of epithelial STAT3 is different from that of stromal STAT3. However, both are essential for blastocyst attachment, suggesting the different roles of epithelial and stromal LIFR in blastocyst implantation. However, how epithelial and stromal LIFR regulate the blastocyst implantation process remains unclear. To investigate the roles of LIFR in the uterine epithelium and stroma, we generated Lifr-floxed/lactoferrin (Ltf)-iCre (Lifr eKO) and Lifr-floxed/antimüllerian hormone receptor type 2 (Amhr2)-Cre (Lifr sKO) mice with deleted epithelial and stromal LIFR, respectively. Surprisingly, fertility and blastocyst implantation in the Lifr sKO mice were normal despite stromal STAT3 inactivation. In contrast, blastocyst attachment failed, and no implantation chambers were formed in the Lifr eKO mice with epithelial inactivation of STAT3. In addition, normal responsiveness to ovarian hormones was observed in the peri-implantation uteri of the Lifr eKO mice. These results indicate that the epithelial LIFR-STAT3 pathway initiates the formation of implantation chambers, leading to complete blastocyst attachment, and that stromal STAT3 regulates blastocyst attachment without stromal LIFR control. Thus, uterine epithelial LIFR is critical to implantation chamber formation and blastocyst attachment.

Cleavage of SPACA1 regulates assembly of sperm-egg membrane fusion machinery in mature spermatozoa†

The acrosome reaction is a multi-step event essential for physiological fertilization. During the acrosome reaction, gamete fusion-related factor IZUMO1 translocates from the anterior acrosome to the equatorial segment and assembles the gamete fusion machinery. The morphological changes in the acrosome reaction process have been well studied, but little is known about the molecular mechanisms of acrosome reorganization essential for physiological gamete membrane fusion. To elucidate the molecular mechanisms of IZUMO1 translocation, the steps of the acrosome reaction during that process must be clarified. In this study, we established a method to detect the early steps of the acrosome reaction and subdivided the process into seven populations through the use of two epitope-defined antibodies, anti-IZUMO1 and anti-SPACA1, a fertilization-inhibiting antibody. We found that part of the SPACA1 C-terminus in the periacrosomal space was cleaved and had begun to disappear when the vesiculation of the anterior acrosome occurred. The IZUMO1 epitope externalized from the acrosomal lumen before acrosomal vesiculation and phosphorylation of IZUMO1 occurred during the translocation to the equatorial segment. IZUMO1 circumvented the area of the equatorial segment where the SPACA1C-terminus was still localized. We therefore propose an IZUMO1 translocation model and involvement of SPACA1.

Comparative Proteomics and Phosphoproteomics Analysis Reveal the Possible Breed Difference in Yorkshire and Duroc Boar Spermatozoa

Sperm cells are of unique elongated structure and function, the development of which is tightly regulated by the existing proteins and the posttranslational modifications (PTM) of these proteins. Based on the phylogenetic relationships of various swine breeds, Yorkshire boar is believed to be distinctly different from Duroc boar. The comprehensive differential proteomics and phosphoproteomics profilings were performed on spermatozoa from both Yorkshire and Duroc boars. By both peptide and PTM peptide quantification followed by statistical analyses, 167 differentially expressed proteins were identified from 1,745 proteins, and 283 differentially expressed phosphopeptides corresponding to 102 unique differentially phosphorylated proteins were measured from 1,140 identified phosphopeptides derived from 363 phosphorylated proteins. The representative results were validated by Western blots. Pathway enrichment analyses revealed that majority of differential expression proteins and differential phosphorylation proteins were primarily concerned with spermatogenesis, male gamete generation, sperm motility, energy metabolism, cilium morphogenesis, axonemal dynein complex assembly, sperm–egg recognition, and capacitation. Remarkably, axonemal dynein complex assembly related proteins, such as SMCP, SUN5, ODF1, AKAP3, and AKAP4 that play a key regulatory role in the sperm physiological functions, were significantly higher in Duroc spermatozoa than that of Yorkshire. Furthermore, phosphorylation of sperm-specific proteins, such as CABYR, ROPN1, CALM1, PRKAR2A, and PRKAR1A, participates in regulation of the boar sperm motility mainly through the cAMP/PKA signal pathway in different breeds, demonstrating that protein phosphorylation may be an important mechanism underlying the sperm diversity. Protein–protein interaction analysis revealed that the 14 overlapped proteins between differential expression proteins and differential phosphorylation proteins potentially played a key role in sperm development and motility of the flagellum, including the proteins ODF1, SMCP, AKAP4, FSIP2, and SUN5. Taken together, these physiologically and functionally differentially expressed proteins (DEPs) and differentially expressed phosphorylated proteins (DPPs) may constitute the proteomic backgrounds between the two different boar breeds. The validation will be performed to delineate the roles of these PTM proteins as modulators of Yorkshire and Duroc boar spermatozoa.

CFAP65 is required in the acrosome biogenesis and mitochondrial sheath assembly during spermiogenesis

Asthenoteratospermia is a common cause of male infertility. Recent studies have revealed that CFAP65 mutations lead to severe asthenoteratospermia due to acrosome hypoplasia and flagellum malformations. However, the molecular mechanism underlying CFAP65-associated sperm malformation is largely unclear. Here, we initially examined the role of CFAP65 during spermiogenesis using Cfap65 knockout (Cfap65-/-) mice. The results showed that Cfap65-/- male mice exhibited severe asthenoteratospermia characterized by morphologically defective sperm heads and flagella. In Cfap65-/- mouse testes, hyper-constricted sperm heads were apparent in step 9 spermatids accompanied by abnormal manchette development, and acrosome biogenesis was abnormal in the maturation phase. Moreover, subsequent flagellar elongation was also severely affected and characterized by disrupted assembly of the mitochondrial sheath (MS) in Cfap65-/- male mice. Furthermore, the proteomic analysis revealed that the proteostatic system during acrosome formation, manchette organization, and MS assembly was disrupted when CFAP65 was lost. Importantly, endogenous immunoprecipitation and immunostaining experiments revealed that CFAP65 may form a cytoplasmic protein network comprising MNS1, RSPH1, TPPP2, ZPBP1, and SPACA1. Overall, these findings provide insights into the complex molecular mechanisms of spermiogenesis by uncovering the essential roles of CFAP65 during sperm head shaping, acrosome biogenesis, and MS assembly.