An update of the regulatory factors of sperm migration from the uterus into the oviduct by genetically manipulated mice

Multi-omics analyses and machine learning prediction of oviductal responses in the presence of gametes and embryos

The oviduct is the site of fertilization and preimplantation embryo development in mammals. Evidence suggests that gametes alter oviductal gene expression. To delineate the adaptive interactions between the oviduct and gamete/embryo, we performed a multi-omics characterization of oviductal tissues utilizing bulk RNA-sequencing (RNA-seq), single-cell RNA-sequencing (scRNA-seq), and proteomics collected from distal and proximal at various stages after mating in mice. We observed robust region-specific transcriptional signatures. Specifically, the presence of sperm induces genes involved in pro-inflammatory responses in the proximal region at 0.5 days post-coitus (dpc). Genes involved in inflammatory responses were produced specifically by secretory epithelial cells in the oviduct. At 1.5 and 2.5 dpc, genes involved in pyruvate and glycolysis were enriched in the proximal region, potentially providing metabolic support for developing embryos. Abundant proteins in the oviductal fluid were differentially observed between naturally fertilized and superovulated samples. RNA-seq data were used to identify transcription factors predicted to influence protein abundance in the proteomic data via a novel machine learning model based on transformers of integrating transcriptomics and proteomics data. The transformers identified influential transcription factors and correlated predictive protein expressions in alignment with the in vivo-derived data. In conclusion, our multi-omics characterization and subsequent in vivo confirmation of proteins/RNAs indicate that the oviduct is adaptive and responsive to the presence of sperm and embryos in a spatiotemporal manner.

SMA20/PMIS2 Is a Rapidly Evolving Sperm Membrane Alloantigen with Possible Species-Divergent Function in Fertilization

Immunodominant alloantigens in pig sperm membranes include 15 known gene products and a previously undiscovered Mr 20,000 sperm membrane-specific protein (SMA20). Here we characterize SMA20 and identify it as the unannotated pig ortholog of PMIS2. A composite SMA20 cDNA encoded a 126 amino acid polypeptide comprising two predicted transmembrane segments and an N-terminal alanine- and proline (AP)-rich region with no apparent signal peptide. The Northern blots showed that the composite SMA20 cDNA was derived from a 1.1 kb testis-specific transcript. A BLASTp search retrieved no SMA20 match from the pig genome, but it did retrieve a 99% match to the Pmis2 gene product in warthog. Sequence identity to predicted PMIS2 orthologs from other placental mammals ranged from no more than 80% overall in Cetartiodactyla to less than 60% in Primates, with the AP-rich region showing the highest divergence, including, in the extreme, its absence in most rodents, including the mouse. SMA20 immunoreactivity localized to the acrosome/apical head of methanol-fixed boar spermatozoa but not live, motile cells. Ultrastructurally, the SMA20 AP-rich domain immunolocalized to the inner leaflet of the plasma membrane, the outer acrosomal membrane, and the acrosomal contents of ejaculated spermatozoa. Gene name search failed to retrieve annotated Pmis2 from most mammalian genomes. Nevertheless, individual pairwise interrogation of loci spanning Atp4a-Haus5 identified Pmis2 in all placental mammals, but not in marsupials or monotremes. We conclude that the gene encoding sperm-specific SMA20/PMIS2 arose de novo in Eutheria after divergence from Metatheria, whereupon rapid molecular evolution likely drove the acquisition of a species-divergent function unique to fertilization in placental mammals.

Comparison of the gene expression profile of testicular tissue before and after sexual maturity in Qianbei Ma goats

BACKGROUND

With long-term research on the reproductive ability of Qianbei Ma goat, we found that the puberty of the male goats comes at the age of 3 months and reaches sexual maturity at 4 months,the male goats are identified as physically mature at 9 months and able to mate. Compared with other kinds of breeds of goats, Qianbei Ma goat is featured with more faster growth and earlier sexual maturity.Therefore, in order to explore the laws of growth of Qianbei Ma goat before sexual maturity(3-month-old)and after sexual maturity (9-month-old). The testicular tissue was collected to explore their changes in morphology through HE staining, the serum was collected to detect the hormone content, and the mRNA expression profile of the testis was analyzed by transcriptomics. In this way, the effect of testicular development on the reproduction of Qianbei ma goats was further analyzed.

RESULTS

The results showed that the area and diameter of spermatogenic tubules were larger at 9 months than 3 months, and the number of spermatocytes, interstitial cells, spermatogonia and secondary spermatocytes in the lumen of the tubules showed a similar trend. The appearance of spermatozoa at age 3 months indicated that puberty had begun in Qianbei Ma goats. The Elasa test for testosterone, luteinizing hormone, follicle stimulating hormone and anti-Müllerian hormone showed that the levels of these hormones in the serum at age 9 months were all highly significantly different than those at age 3 months (P < 0.01). There were 490 differentially expressed genes (DEGs) between the (|log2(fold change)| > 1 and p value < 0.05) 3-month-old and 9-month-old groups, of which 233 genes were upregulated and 257 genes were downregulated (3 months of age was used as the control group and 9 months of age was used as the experimental group). According to the GO and KEGG enrichment analyses of DEGs, PRSS58, ECM1, WFDC8 and LHCGR are involved in testicular development and androgen secretion, which contribute to the sexual maturation of Qianbei Ma goats.

CONCLUSIONS

Potential biomarker genes and relevant pathways involved in the regulation of testicular development and spermatogenesis in Qianbei Ma goats were identified, providing a theoretical basis and data support for later studies on the influence of testicular development and spermatogenesis before and after sexual maturity in Qianbei Ma goats.

Sperm in the Mammalian Female Reproductive Tract: Surfing Through the Tract to Try to Beat the Odds

Mammalian sperm are deposited in the vagina or the cervix/uterus at coitus or at artificial insemination, and the fertilizing sperm move through the female reproductive tract to the ampulla of the oviduct, the site of fertilization. But the destination of most sperm is not the oviduct. Most sperm are carried by retrograde fluid flow to the vagina, are phagocytosed, and/or do not pass barriers on the pathway to the oviduct. The sperm that reach the site of fertilization are the exceptions and winners of one of the most stringent selection processes in nature. This review discusses the challenges sperm encounter and how the few sperm that reach the site of fertilization overcome them. The sperm that reach the goal must navigate viscoelastic fluid, swim vigorously and cooperatively along the walls of the female tract, avoid the innate immune system, and respond to potential cues to direct their movement.

The Application of Ejaculate-Based Shotgun Proteomics for Male Infertility Screening

Problems with the male reproductive system are of both medical and social significance. As a rule, spermatozoa and seminal plasma proteomes are investigated separately to assess sperm quality. The current study aimed to compare ejaculate proteomes with spermatozoa and seminal plasma protein profiles regarding the identification of proteins related to fertility scores. A total of 1779, 715, and 2163 proteins were identified in the ejaculate, seminal plasma, and spermatozoa, respectively. Among these datasets, 472 proteins were shared. GO enrichment analysis of the common proteins enabled us to distinguish biological processes such as single fertilization (GO:0007338), spermatid development (GO:0007286), and cell motility (GO:0048870). Among the abundant terms for GO cellular components, zona pellucida receptor complex, sperm fibrous sheath, and outer dense fiber were revealed. Overall, we identified 139 testis-specific proteins. For these proteins, PPI networks that are common in ejaculate, spermatozoa, and seminal plasma were related to the following GO biological processes: cilium movement (GO:0003341), microtubule-based movement (GO:0007018), and sperm motility (GO:0097722). For ejaculate and spermatozoa, they shared 15 common testis-specific proteins with spermatogenesis (GO:0007283) and male gamete generation (GO:0048232). Therefore, we speculated that ejaculate-based proteomics could yield new insights into the peculiar reproductive physiology and spermatozoa function of men and potentially serve as an explanation for male infertility screening.

Molecular dissection and testing of PRSS37 function through LC-MS/MS and the generation of a PRSS37 humanized mouse model

The quest for a non-hormonal male contraceptive pill for men still exists. Serine protease 37 (PRSS37) is a sperm-specific protein that when ablated in mice renders them sterile. In this study we sought to examine the molecular sequelae of PRSS37 loss to better understand its molecular function, and to determine whether human PRSS37 could rescue the sterility phenotype of knockout (KO) mice, allowing for a more appropriate model for drug molecule testing. To this end, we used CRISPR-EZ to create mice lacking the entire coding region of Prss37, used pronuclear injection to create transgenic mice expressing human PRSS37, intercrossed these lines to generate humanized mice, and performed LC-MS/MS of KO and control tissues to identify proteomic perturbances that could attribute a molecular function to PRSS37. We found that our newly generated Prss37 KO mouse line is sterile, our human transgene rescues the sterility phenotype of KO mice, and our proteomics data not only yields novel insight into the proteome as it evolves along the male reproductive tract, but also demonstrates the proteins significantly influenced by PRSS37 loss. In summary, we report vast biological insight including insight into PRSS37 function and the generation of a novel tool for contraceptive evaluation.

Impaired fertility in 4930590J08Rik mutant male mice is associated with defective sperm energy metabolism

Testis-specifically expressed genes are important for male reproduction according to their unique expression patterns. However, the functions of most of these genes in reproduction are unclear. Here, we showed that mouse 4930590J08Rik was a testis-specifically expressed gene. 4930590J08Rik knockout mice exhibited a delay in the first wave of spermatogenesis and a reduction of cauda epididymal sperm. Furthermore, knockout spermatozoa exhibited defective acrosome reactions and decreased progressive motility, which led to impaired in vivo fertilization. Transcriptome analysis of testes revealed that most of the differentially expressed genes in knockout testes were associated with metabolic processes. 4930590J08Rik knockout sperm exhibited oxidative phosphorylation deficiency and were highly dependent on increased anaerobic glycolysis to compensate for ATP demands. Taken together, the 4930590J08Rik-disrupted mouse partially mimics the phenotypes of human asthenospermia and oligozoospermia, which provides a new model for further understanding the pathogenesis of idiopathic male infertility.

Testis-specific serine protease PRSS54 regulates acrosomal granule localization and sperm head morphogenesis in mice

Serine proteases (PRSS) constitute nearly one-third of all proteases, and many of them have been identified to be testis-specific and play significant roles during sperm development and male reproduction. PRSS54 is one of the testis-specific PRSS in mouse and human but its physiological function remains largely unclear. In the present study, we demonstrate in detail that PRSS54 exists not only in testis but also in mature sperm, exhibiting a change in protein size from 50 kDa in testis to 42 kDa in sperm. Loss of PRSS54 in mice results in male subfertility, acrosome deformation, defective sperm-zona penetration, and phenotypes of male subfertility and acrosome deformation can be rescued by Prss54 transgene. Ultrastructure analyses by transmission electronic microscopy further reveal various morphological abnormalities of Prss54-/- spermatids during spermiogenesis, including unfused vacuoles in acrosome, detachment and eccentrical localization of the acrosomal granules, and asymmetrical elongation of the nucleus. Subcellular localization of PRSS54 display that it appears in the acrosomal granule at the early phase of acrosome biogenesis, then extends along the inner acrosomal membrane, and ultimately presents in the acrosome region of the mature sperm. PRSS54 interacts with acrosomal proteins ZPBP1, ZPBP2, ACRBP and ZP3R, and loss of PRSS54 affects the distribution of these proteins in testis and sperm, although their protein levels are largely unaffected. Moreover, Prss54-/- sperm are more sensitive to acrosome reaction inducers. These data indicate that PRSS54 is an acrosomal protein and plays an important role in regulating acrosome biogenesis, sperm function and male fertility.

The cell biology of fertilization: Gamete attachment and fusion

Fertilization is defined as the union of two gametes. During fertilization, sperm and egg fuse to form a diploid zygote to initiate prenatal development. In mammals, fertilization involves multiple ordered steps, including the acrosome reaction, zona pellucida penetration, sperm-egg attachment, and membrane fusion. Given the success of in vitro fertilization, one would think that the mechanisms of fertilization are understood; however, the precise details for many of the steps in fertilization remain a mystery. Recent studies using genetic knockout mouse models and structural biology are providing valuable insight into the molecular basis of sperm-egg attachment and fusion. Here, we review the cell biology of fertilization, specifically summarizing data from recent structural and functional studies that provide insights into the interactions involved in human gamete attachment and fusion.

Adam21 is dispensable for reproductive processes in mice

BACKGROUND

As a group of membrane-anchored proteins, the proteins containing a disintegrin and metalloprotease domain (ADAMs) control many biological processes, especially for male fertility. Mouse Adam21 was previously found to be specifically expressed in the somatic cells and germ cells of testes, but its functional role during spermatogenesis and male reproductive processes is still unknown.

METHODS

Adam21-null mice were created using the CRISPR/Cas9 system. Quantitative real-time PCR was used for analyzing of gene expression. Histological, cytological and immunofluorescence staining were performed to analyze the phenotypes of mouse testis and epididymis. Intracellular lipid droplets (LDs) were detected by Oil red O (ORO) staining and BODIPY staining. Fertility and sperm characteristics were also detected.

RESULTS

Here, we successfully generated an Adam21 conventional knockout mouse model via CRISPR/Cas9 technology so that we can explore its potential role in male reproduction. We found that male mice lacking Adam21 have normal fertility without any detectable defects in spermatogenesis or sperm motility. Histological analysis of the seminiferous epithelium showed no obvious spermatogenesis difference between Adam21-null and wild-type mice. Cytological analysis revealed no detectable defects in meiotic progression, neither Sertoli cells nor Leydig cells displayed any defect compared with that of the control mice. All these results suggest that Adam21 might not be essential for male fertility in mice, and its potential function still needs further investigation.

Dissecting the PRSS37 interactome and potential mechanisms leading to ADAM3 loss in PRSS37-null sperm

A disintegrin and metalloproteinase 3 (ADAM3) is a sperm membrane protein critical for sperm migration from the uterus into the oviduct and sperm-egg binding in mice. Disruption of PRSS37 results in male infertility concurrent with the absence of mature ADAM3 from cauda epididymal sperm. However, how PRSS37 modulates ADAM3 maturation remains largely unclear. Here, we determine the PRSS37 interactome by GFP immunoprecipitation coupled with mass spectrometry in PRSS37-EGFP knock-in mice. Three molecular chaperones (CLGN, CALR3 and PDILT) and three ADAM proteins (ADAM2, ADAM6B and ADAM4) were identified to be interacting with PRSS37. Coincidently, five of them (except ADAM4) have been reported to interact with ADAM3 precursor and regulate its maturation. We further demonstrated that PRSS37 also interacts directly with ADAM3 precursor and its deficiency impedes the association between PDILT and ADAM3. This could contribute to improper translocation of ADAM3 to the germ cell surface, leading to ADAM3 loss in PRSS37-null mature sperm. The understanding of the maturation mechanisms of pivotal sperm plasma membrane proteins will pave the way toward novel strategies for contraception and the treatment of unexplained male infertility.

The enigmatic sperm proteins in mammalian fertilization: an overview†

Mammalian fertilization involves a physical interaction between a sperm and an egg followed by molecular interactions amongst their various cell surface molecules. These interactions are initially mediated on the egg's outermost matrix, zona pellucida (ZP), and then its plasma membrane. To better understand this process, it is pertinent to find the corresponding molecules on sperm that interact with ZP or the egg's plasma membrane. Although currently, we have some knowledge about the binding partners for egg's plasma membrane on sperm, yet the ones involved in an interaction with ZP have remained remarkably elusive. This review provides comprehensive knowledge about the various sperm proteins participating in mammalian fertilization and discusses the possible reasons for not being able to identify the strong sperm surface candidate (s) for ZP adhesion. It also hypothesizes the existence of a multi-protein complex(s), members of which participate in oviduct transport, cumulus penetration, zona adhesion, and adhesion/fusion with the egg's plasma membrane; with some protein(s) having multiple roles during this process. Identification of these proteins is crucial as it improves our understanding of the process and allows us to successfully treat infertility, develop contraceptives, and improve artificial reproductive technologies.

Sperm interactions with the female reproductive tract: A key for successful fertilization in mammals

Sperm migration through the female genital tract is not a quiet journey. Uterine contractions quickly operate a drastic selection, leading to a very restrictive number of sperm reaching the top of uterine horns and finally, provided the presence of key molecules on sperm, the oviduct, where fertilization takes place. During hours and sometimes days before fertilization, subpopulations of spermatozoa interact with dynamic and region-specific maternal components, including soluble proteins, extracellular vesicles and epithelial cells lining the lumen of the female tract. Interactions with uterine and oviductal cells play important roles for sperm survival as they modulate the maternal immune response and allow a transient storage before ovulation. The body of work reported here highlights the importance of sperm interactions with proteins originated from both the uterine and oviductal fluids, as well as hormonal signals around the time of ovulation for sperm acquisition of fertilizing competence.

Tmprss12 is required for sperm motility and uterotubal junction migration in mice†

Spermatozoa are produced in the testis but gain their fertilizing ability during epididymal migration. This necessary step in sperm maturation includes posttranslational modification of sperm membrane proteins that includes protein processing by proteases. However, the molecular mechanism underpinning this epididymal sperm maturation remains unknown. In this study, we focused on transmembrane serine protease 12 (Tmprss12). Based on multi-tissue expression analysis by PCR, Tmprss12 was specifically expressed in the testis, and its expression started on day 10 postpartum, corresponding to the stage of zygotene spermatocytes. TMPRSS12 was detected in the acrosomal region of spermatozoa by immunostaining. To reveal the physiological function of TMPRSS12, we generated two knockout (KO) mouse lines using the CRISPR/Cas9 system. Both indel and large deletion lines were male sterile showing that TMPRSS12 is essential for male fertility. Although KO males exhibited normal spermatogenesis and sperm morphology, ejaculated spermatozoa failed to migrate from the uterus to the oviduct. Further analysis revealed that a disintegrin and metalloprotease 3 (ADAM3), an essential protein on the sperm membrane surface that is required for sperm migration, was disrupted in KO spermatozoa. Moreover, we found that KO spermatozoa showed reduced sperm motility via computer-assisted sperm analysis, resulting in a low fertilization rate in vitro. Taken together, these data indicate that TMPRSS12 has dual functions in regulating sperm motility and ADAM3-related sperm migration to the oviduct. Because Tmprss12 is conserved among mammals, including humans, our results may explain some genetic cases of idiopathic male infertility, and TMPRSS12 and its downstream cascade may be novel targets for contraception.

Male fertility in Mus musculus requires the activity of TRYX5 in sperm migration into the oviduct

Nowadays, abnormal loss of serine proteases appears very frequently in male patients with unexplained sterility. In fact, many testis-specific serine proteases, the largest family among the four protease families implicated in murine spermatogenesis, are indispensable for reproduction. In the present study, we demonstrate that the previously uncharacterized testis-specific serine protease TRYX5 (1700074P13Rik) is required for male fertility in mice. Tryx5^-/- male mice are sterile, yet they have normal spermatogenesis and normal sperm parameters. In vivo fertilization experiments showed that the fertilization rate of Tryx5^-/- sperm was almost zero. Sperm counting and analysis of paraffin sections of oviducts revealed that Tryx5^-/- sperm were unable to migrate into the oviduct, which is likely the cause of the observed infertility of the Tryx5^-/- male mice. Importantly, we also found that there was almost no mature ADAM3 present in Tryx5^-/- sperm and almost no ADAM3 precursor in Tryx5^-/- elongated spermatids of S13-16 stage, even though testes of Tryx5^-/- and wild type mice had the same amount of the total precursor ADAM3. Collectively, our results demonstrate that Tryx5 is essential for male fertility in mice and suggest that TRYX5 functions in the stability or localization of ADAM3 precursor in elongated spermatids S13-16 stage, thereby regulating the ability of sperm to migrate from the uterus into the ampulla of the oviduct, the site of fertilization.

Adhesion molecules in gamete transport, fertilization, early embryonic development, and implantation-role in establishing a pregnancy in cattle: A review

Cell-cell adhesion molecules have critically important roles in the early events of reproduction including gamete transport, sperm-oocyte interaction, embryonic development, and implantation. Major adhesion molecules involved in reproduction include cadherins, integrins, and disintegrin and metalloprotease domain-containing (ADAM) proteins. ADAMs on the surface of sperm adhere to integrins on the oocyte in the initial stages of sperm-oocyte interaction and fusion. Cadherins act in early embryos to organize the inner cell mass and trophectoderm. The trophoblast and uterine endometrial epithelium variously express cadherins, integrins, trophinin, and selectin, which achieve apposition and attachment between the elongating conceptus and uterine epithelium before implantation. An overview of the major cell-cell adhesion molecules is presented and this is followed by examples of how adhesion molecules help shape early reproductive events. The argument is made that a deeper understanding of adhesion molecules and reproduction will inform new strategies that improve embryo survival and increase the efficiency of natural mating and assisted breeding in cattle.

Two novel testis-specific long noncoding RNAs produced by <i>1700121C10Rik</i> are dispensable for male fertility in mice

Testis-specific genes are prone to affect spermatogenesis or sperm fertility, and thus may play pivotal roles in male reproduction. However, whether a gene really affects male reproduction in vivo needs to be confirmed using a gene knock-out (KO) model, a ‘gold standard’ method. Increasing studies have found that some of the evolutionarily conserved testis-enriched genes are not essential for male fertility. In this study, we report that 1700121C10Rik, a previously uncharacterized gene, is specifically expressed in the testis and produces two long noncoding RNAs (lncRNAs) in mouse: Transcript 1 and Transcript 2. qRT-PCR, northern blotting, and in situ hybridization revealed that expression of both the lncRNAs commenced at the onset of sexual maturity and was predominant in round and elongating spermatids during spermiogenesis. Moreover, we found different subcellular localization of Transcript 1 and Transcript 2 that was predominant in the cytoplasm and nucleus, respectively. 1700121C10Rik-KO mouse model disrupting Transcript 1 and Transcript 2 expression was generated by CRISPR/Cas9 to determine their role in male reproduction. Results showed that 1700121C10Rik-KO male mice were fully fertile with approximately standard testis size, testicular histology, sperm production, sperm morphology, sperm motility, and induction of acrosome reaction. Thus, we conclude that both the testis-specific 1700121C10Rik-produced lncRNAs are dispensable for male fertility in mice under standard laboratory conditions.

Sperm IZUMO1-Dependent Gamete Fusion Influences Male Fertility in Mice

Sperm–egg fusion is accomplished through the interaction of a specific set of membrane proteins in each gamete: sperm IZUMO1 and oocyte JUNO. Recently, we found that alternative splicing of the Izumo1 gene generates a novel IZUMO1 isoform (IZUMO1_v2). Here, we obtained four mouse lines, having graded different levels of IZUMO1 protein by combining an original IZUMO1 (IZUMO1_v1) knockout with IZUMO1-null (both IZUMO1_v1 and _v2 disrupted) genetic background, in order to determine how the quantity of IZUMO1 influences male fertility. Subsequently, we clarified that the signal intensity from two quantitative assays, western blot and immunostaining analyses with a monoclonal antibody against mouse IZUMO1, were strongly correlated with average litter size. These results suggest that evaluating IZUMO1 protein levels is useful for predicting fecundity, and is a suitable test for male fertility.