Classification of mouse sperm motility patterns using an automated multiclass support vector machines model

Epididymal and ejaculated sperm differ on their response to the cryopreservation and capacitation processes in mouflon (Ovis musimon)

Spermatozoa must undergo the process of capacitation to fertilize the egg which involves a cell destabilizing process. Capacitation-like changes such as protein tyrosine phosphorylation (PTP) are associated with cryopreservation. The aim of this study was to compare the cryoresistance and capacitation response of epididymal and ejaculated sperm of European mouflon (Ovis musimon). Post-thaw sperm parameters were analysed from epididymal and ejaculated samples cryopreserved by slow-freezing or ultrarapid-freezing for comparison. Sperm capacitation status was assessed by the semiquantification of PTP levels, cell localization of PTP and kinematic clustering. Epididymal sperm had higher cryoresistance than ejaculated sperm in both freezing techniques, and slow-freezing rendered better results than ultrarapid-freezing in both sperm samples. Ejaculated sperm had higher PTP levels than epididymal sperm and, additionally, ejaculated sperm showed higher phosphorylation in capacitating (CA) than in non-capacitating (NCA) conditions while there was no effect of medium in epididymal sperm. There was a higher tail PTP in CA than in NCA conditions in both types of sperm. Kinematic analysis revealed that the cluster associated with hyperactivated movement increased in ejaculated sperm incubated in CA whereas no effect of medium was observed in epididymal sperm clusters. In conclusion, epididymal sperm showed better freezability and lower capacitation status compared to ejaculated sperm.

Protective effects of Curcumin on testicular toxicity induced by titanium dioxide nanoparticles in mice

Objective:

In this study, we investigated the preventing effects of Curcumin (Cur) against titanium dioxide nanoparticle (NTiO₂)-induced mouse testicular damage.

Methods:

We assessed NTiO₂-intoxicated mice received 50mg/kg of NTiO₂ for 35 days. The Cur + NTiO₂ group was pretreated with Cur (200 mg/kg) for 7 days prior to administering NTiO₂. Sperm parameters, testosterone concentration, histological criteria, morphometric parameters and Johnsen's scoring.

Results:

NTiO₂ significantly reduced testicular weight, testosterone concentration, morphometric parameters, Johnsen's scoring and sperm quality (p<0.01), as well as a significant increase in histological criteria. Pretreatment with Cur reduced testicular weight, ameliorated morphometric parameters, increased Johnsen's scoring, elevated testosterone levels, and increased histological criteria such as vacuolization, detachment, and sloughing of germ cells into the seminiferous tubules. Cur also improved sperm parameters including sperm count, motility, and percentage of abnormality.

Conclusion:

Cur was found to have a potent protective effect against spermatogenesis defects induced by nanoparticles in mice.

Artificial intelligence in reproductive medicine

Artificial intelligence (AI) has experienced rapid growth over the past few years, moving from the experimental to the implementation phase in various fields, including medicine. Advances in learning algorithms and theories, the availability of large datasets and improvements in computing power have contributed to breakthroughs in current AI applications. Machine learning (ML), a subset of AI, allows computers to detect patterns from large complex datasets automatically and uses these patterns to make predictions. AI is proving to be increasingly applicable to healthcare, and multiple machine learning techniques have been used to improve the performance of assisted reproductive technology (ART). Despite various challenges, the integration of AI and reproductive medicine is bound to give an essential direction to medical development in the future. In this review, we discuss the basic aspects of AI and machine learning, and we address the applications, potential limitations and challenges of AI. We also highlight the prospects and future directions in the context of reproductive medicine.

E-Cigarette Exposure Delays Implantation and Causes Reduced Weight Gain in Female Offspring Exposed In Utero

Electronic nicotine delivery system (e-cigarette) use is prevalent among pregnant women as a seemingly safe alternative to traditional tobacco use, known to result in fetal developmental abnormalities and impaired fertility of male offspring. However, little is known about the effects of e-cigarette use on fertility or pregnancy outcomes. A successful pregnancy is initiated by a multitude of dynamic molecular alterations in the uterus resulting in embryo implantation at day 4.5 in the mouse. We examined whether e-cigarette exposure impairs implantation and offspring health. Pregnant C57BL/6J mice were exposed five times a week to e-cigarette vapor or sham. After 4 months, e-cigarette exposed dams exhibited a significant delay in the onset of the first litter. Furthermore, exposure of new dams in early pregnancy significantly impaired embryo implantation, as evidenced by nearly complete absence of implantation sites in e-cigarette-exposed animals at day 5.5, despite exhibiting high levels of progesterone, an indicator of pregnancy. RNA microarray from day 4.5 pseudopregnant mice revealed significant changes in the integrin, chemokine, and JAK signaling pathways. Moreover, female offspring exposed to e-cigarettes in utero exhibited a significant weight reduction at 8.5 months, whereas males exhibited a slight but nonsignificant deficiency in fertility. Thus, e-cigarette exposure in mice impairs pregnancy initiation and fetal health, suggesting that e-cigarette use by reproductive-aged women or during pregnancy should be considered with caution.

A Peptide-Based Virus Inactivator Protects Male Mice Against Zika Virus-Induced Damage of Testicular Tissue

Zika virus (ZIKV) was a re-emerging arbovirus associated with Guillain–Barré Syndrome in adult and congenital Zika syndrome in fetus and infant. Although ZIKV was mainly transmitted by mosquito bites, many sexual transmission cases have been reported since the outbreak in 2015. ZIKV can persist in testis and semen for a long time, causing testicular tissue damage and reducing sperm quality. However, no drug has been approved for prevention or treatment of ZIKV infection, especially infection in male testicular tissue. Previously reported peptide Z2 could inactivate ZIKV, inhibiting ZIKV infection in vitro and in vivo. Importantly, Z2 could inhibit vertical transmission of ZIKV in pregnant mice, reducing ZIKV infection in fetus. Here we showed that intraperitoneally administered Z2 could also be distributed to testis and epididymis, resulting in the reduction of ZIKV RNA copies in testicular tissue and protection of testis and epididymis against ZIKV-induced pathological damage and poor sperm quality in type I interferon receptor-deficient A129 mice. Thus, Z2, a ZIKV inactivator, could serve as an antiviral agent for treatment of ZIKV infection and attenuation of ZIKV-induced testicular tissue damage.

Intracellular Ca2+ threshold reversibly switches flagellar beat off and on

Sperm motility is essential for fertilization. The asymmetry of flagellar beat in spermatozoa is finely regulated by intracellular calcium concentration ([Ca2+]i). Recently, we demonstrated that the application of high concentrations (10-20 μM) of the Ca2+ ionophore A23187 promotes sperm immobilization after 10 min, and its removal thereafter allows motility recovery, hyperactivation, and fertilization. In addition, the same ionophore treatment overcomes infertility observed in sperm from Catsper1-/-, Slo3-/-, and Adcy10-/-, but not PMCA4-/-, which strongly suggest that regulation of [Ca2+]i is mandatory for sperm motility and hyperactivation. In this study, we found that prior to inducing sperm immobilization, high A23187 concentrations (10 μM) increase flagellar beat. While 5-10 μM A23187 substantially elevates [Ca2+]i and rapidly immobilizes sperm in a few minutes, smaller concentrations (0.5 and 1 μM) provoke smaller [Ca2+]i increases and sperm hyperactivation, confirming that [Ca2+]i increases act as a motility switch. Until now, the [Ca2+]i thresholds that switch motility on and off were not fully understood. To study the relationship between [Ca2+]i and flagellar beating, we developed an automatic tool that allows the simultaneous measurement of these two parameters. Individual spermatozoa were treated with A23187, which is then washed to evaluate [Ca2+]i and flagellar beat recovery using the implemented method. We observe that [Ca2+]i must decrease below a threshold concentration range to facilitate subsequent flagellar beat recovery and sperm motility.

Implementation of novel statistical procedures and other advanced approaches to improve analysis of CASA data

Computer-aided sperm analysis (CASA) produces a wealth of data that is frequently ignored. The use of multiparametric statistical methods can help explore these datasets, unveiling the subpopulation structure of sperm samples. In this review we analyse the significance of the internal heterogeneity of sperm samples and its relevance. We also provide a brief description of the statistical tools used for extracting sperm subpopulations from the datasets, namely unsupervised clustering (with non-hierarchical, hierarchical and two-step methods) and the most advanced supervised methods, based on machine learning. The former method has allowed exploration of subpopulation patterns in many species, whereas the latter offering further possibilities, especially considering functional studies and the practical use of subpopulation analysis. We also consider novel approaches, such as the use of geometric morphometrics or imaging flow cytometry. Finally, although the data provided by CASA systems provides valuable information on sperm samples by applying clustering analyses, there are several caveats. Protocols for capturing and analysing motility or morphometry should be standardised and adapted to each experiment, and the algorithms should be open in order to allow comparison of results between laboratories. Moreover, we must be aware of new technology that could change the paradigm for studying sperm motility and morphology.

Glycerol kinase 2 is essential for proper arrangement of crescent-like mitochondria to form the mitochondrial sheath during mouse spermatogenesis

The mitochondrial sheath is composed of mitochondria that coil tightly around the midpiece of sperm flagellum. These mitochondria are recruited from the cytoplasm to the flagellum late in spermatogenesis. Initially, recruited mitochondria are spherical-shaped but then elongate laterally to become crescent-like in shape. Subsequently, crescent-like mitochondria elongate continuously to coil tightly around the flagellum. Recently, disorganization of the mitochondrial sheath was reported in Glycerol kinase 2 (Gk2) disrupted mice. To analyze the disorganization of the mitochondrial sheath further, we generated Gk2-deficient mice using the CRISPR/Cas9 system and observed sperm mitochondria in testis using a freeze-fracture method with scanning electron microscopy. Gk2-disrupted spermatids show abnormal localization of crescent-like mitochondria, in spite of the initial proper alignment of spherical mitochondria around the flagellum, which causes abnormal mitochondrial sheath formation leading to exposure of the outer dense fibers. These results indicate that GK2 is essential for proper arrangement of crescent-like mitochondria to form the mitochondrial sheath during mouse spermatogenesis.

New Insight into Sperm Capacitation: A Novel Mechanism of 17β-Estradiol Signalling

17β-estradiol (estradiol) is a natural estrogen regulating reproduction including sperm and egg development, sperm maturation—called capacitation—and sperm–egg communication. High doses can increase germ cell apoptosis and decrease sperm count. Our aim was to answer the biological relevance of estradiol in sperm capacitation and its effect on motility and acrosome reaction to quantify its interaction with estrogen receptors and propose a model of estradiol action during capacitation using kinetic analysis. Estradiol increased protein tyrosine phosphorylation, elevated rate of spontaneous acrosome reaction, and altered motility parameters measured Hamilton-Thorne Computer Assisted Semen Analyzer (CASA) in capacitating sperm. To monitor time and concentration dependent binding dynamics of extracellular estradiol, high-performance liquid chromatography with tandem mass spectrometry was used to measure sperm response and data was subjected to kinetic analysis. The kinetic model of estradiol action during sperm maturation shows that estradiol adsorption onto a plasma membrane surface is controlled by Langmuir isotherm. After, when estradiol passes into the cytoplasm, it forms an unstable adduct with cytoplasmic receptors, which display a signalling autocatalytic pattern. This autocatalytic reaction suggests crosstalk between receptor and non-receptor pathways utilized by sperm prior to fertilization.

Calibration of sperm concentration for in vitro fertilization in a mouse reprotoxicity model

Xenobiotics, such as chemicals and pesticides, may result in adverse effects on reproduction in human and animals. Using in-vitro embryo production as a testing system reveals details of fertilization (IVF) and early embryonic development (IVC). The aim of our study was to perform a systematical calibration of sperm concentration in an IVF/IVC system, using an outbred mouse strain, and further determine the sperm concentration that furnishes a sensitive assessment of sperm fertilizing capacity in relation to reprotoxic evaluations. By performing breakpoint analysis, the results revealed a maximum two-cell percentage (51%, 95% CI: 38 to 69%) at 3.6 × 10⁴ sperm/ml (95% CI: 2.1 × 10⁴ to 6.1 × 10⁴). For future application of the IVF/IVC system, a sperm concentration lower than this breakpoint concentration is required to be within the responsive range for determining sperm fertilizing capacity. We conclude that a relatively low sperm concentration (2.5 × 10⁴ sperm/ml) is a precondition in a mouse IVF/IVC system in order to detect potential reprotoxic effects on sperm fertilizing capacity. Our study illustrates that a systematic approach is necessary for validation and appropriate use of such in-vitro system used for reproductive toxicity testing.

mDia1/3 generate cortical F-actin meshwork in Sertoli cells that is continuous with contractile F-actin bundles and indispensable for spermatogenesis and male fertility

Formin is one of the two major classes of actin binding proteins (ABPs) with nucleation and polymerization activity. However, despite advances in our understanding of its biochemical activity, whether and how formins generate specific architecture of the actin cytoskeleton and function in a physiological context in vivo remain largely obscure. It is also unknown how actin filaments generated by formins interact with other ABPs in the cell. Here, we combine genetic manipulation of formins mammalian diaphanous homolog1 (mDia1) and 3 (mDia3) with superresolution microscopy and single-molecule imaging, and show that the formins mDia1 and mDia3 are dominantly expressed in Sertoli cells of mouse seminiferous tubule and together generate a highly dynamic cortical filamentous actin (F-actin) meshwork that is continuous with the contractile actomyosin bundles. Loss of mDia1/3 impaired these F-actin architectures, induced ectopic noncontractile espin1-containing F-actin bundles, and disrupted Sertoli cell-germ cell interaction, resulting in impaired spermatogenesis. These results together demonstrate the previously unsuspected mDia-dependent regulatory mechanism of cortical F-actin that is indispensable for mammalian sperm development and male fertility.

CASAnova: a multiclass support vector machine model for the classification of human sperm motility patterns

The ability to accurately monitor alterations in sperm motility is paramount to understanding multiple genetic and biochemical perturbations impacting normal fertilization. Computer-aided sperm analysis (CASA) of human sperm typically reports motile percentage and kinematic parameters at the population level, and uses kinematic gating methods to identify subpopulations such as progressive or hyperactivated sperm. The goal of this study was to develop an automated method that classifies all patterns of human sperm motility during in vitro capacitation following the removal of seminal plasma. We visually classified CASA tracks of 2817 sperm from 18 individuals and used a support vector machine-based decision tree to compute four hyperplanes that separate five classes based on their kinematic parameters. We then developed a web-based program, CASAnova, which applies these equations sequentially to assign a single classification to each motile sperm. Vigorous sperm are classified as progressive, intermediate, or hyperactivated, and nonvigorous sperm as slow or weakly motile. This program correctly classifies sperm motility into one of five classes with an overall accuracy of 89.9%. Application of CASAnova to capacitating sperm populations showed a shift from predominantly linear patterns of motility at initial time points to more vigorous patterns, including hyperactivated motility, as capacitation proceeds. Both intermediate and hyperactivated motility patterns were largely eliminated when sperm were incubated in noncapacitating medium, demonstrating the sensitivity of this method. The five CASAnova classifications are distinctive and reflect kinetic parameters of washed human sperm, providing an accurate, quantitative, and high-throughput method for monitoring alterations in motility.

Molecular Basis of Human Sperm Capacitation

In the early 1950s, Austin and Chang independently described the changes that are required for the sperm to fertilize oocytes in vivo. These changes were originally grouped under name of “capacitation” and were the first step in the development of in vitro fertilization (IVF) in humans. Following these initial and fundamental findings, a remarkable number of observations led to characterization of the molecular steps behind this process. The discovery of certain sperm-specific molecules and the possibility to record ion currents through patch-clamp approaches helped to integrate the initial biochemical observation with the activity of ion channels. This is of particular importance in the male gamete due to the fact that sperm are transcriptionally inactive. Therefore, sperm must control all these changes that occur during their transit through the male and female reproductive tracts by complex signaling cascades that include post-translational modifications. This review is focused on the principal molecular mechanisms that govern human sperm capacitation with particular emphasis on comparing all the reported pieces of evidence with the mouse model.

Only a subpopulation of mouse sperm displays a rapid increase in intracellular calcium during capacitation

Mammalian sperm must undergo a functionally defined process called capacitation to be able to fertilize oocytes. They become capacitated in vivo by interacting with the female reproductive tract or in vitro in a defined capacitation medium that contains bovine serum albumin, calcium (Ca²⁺ ), and bicarbonate (HCO₃ ^- ). In this work, sperm were double stained with propidium iodide and the Ca²⁺ dye Fluo-4 AM and analyzed by flow cytometry to determine changes in intracellular Ca²⁺ concentration ([Ca²⁺ ]_i ) in individual live sperm. An increase in [Ca²⁺ ]_i was observed in a subpopulation of capacitated live sperm when compared with noncapacitated ones. Sperm exposed to the capacitating medium displayed a rapid increase in [Ca²⁺ ]_i within 1 min of incubation, which remained sustained for 90 min. These rise in [Ca²⁺ ]_i after 90 min of incubation in the capacitating medium was evidenced by an increase in the normalized median fluorescence intensity. This increase was dependent on the presence of extracellular Ca²⁺ and, at least in part, reflected the contribution of a new subpopulation of sperm with higher [Ca²⁺ ]_i . In addition, it was determined that the capacitation-associated [Ca²⁺ ]_i increase was dependent of CatSper channels, as sperm derived from CatSper knockout (CatSper KO) or incubated in the presence of CatSper inhibitors failed to increase [Ca²⁺ ]_i . Surprisingly, a minimum increase in [Ca²⁺ ]_i was also observed in CatSper KO sperm suggesting the existence of other Ca²⁺ transport systems. Altogether, these results indicate that a subpopulation of sperm increases [Ca²⁺ ]_i very rapidly during capacitation mainly due to a CatSper-mediated influx of extracellular Ca²⁺ .

Disruption of protein kinase A localization induces acrosomal exocytosis in capacitated mouse sperm

Protein kinase A (PKA) is a broad-spectrum Ser/Thr kinase involved in the regulation of several cellular activities. Thus, its precise activation relies on being localized at specific subcellular places known as discrete PKA signalosomes. A-Kinase anchoring proteins (AKAPs) form scaffolding assemblies that play a pivotal role in PKA regulation by restricting its activity to specific microdomains. Because one of the first signaling events observed during mammalian sperm capacitation is PKA activation, understanding how PKA activity is restricted in space and time is crucial to decipher the critical steps of sperm capacitation. Here, we demonstrate that the anchoring of PKA to AKAP is not only necessary but also actively regulated during sperm capacitation. However, we find that once capacitated, the release of PKA from AKAP promotes a sudden Ca²⁺ influx through the sperm-specific Ca²⁺ channel CatSper, starting a tail-to-head Ca²⁺ propagation that triggers the acrosome reaction. Three-dimensional super-resolution imaging confirmed a redistribution of PKA within the flagellar structure throughout the capacitation process, which depends on anchoring to AKAP. These results represent a new signaling event that involves CatSper Ca²⁺ channels in the acrosome reaction, sensitive to PKA stimulation upon release from AKAP.

Vitamin C exerts novel protective effects against cadmium toxicity in mouse spermatozoa by inducing the dephosphorylation of dihydrolipoamide dehydrogenase

Cadmium (Cd) has been reported to inhibit mouse sperm motility by inducing the tyrosine phosphorylation of dihydrolipoamide dehydrogenase (DLD). This study aimed to assess the potential effects of vitamin C (Vc) on ameliorating Cd-induced tyrosine phosphorylation of DLD and the specific underlying mechanism. Vc induced the dephosphorylation of DLD or inhibited the tyrosine phosphorylation of DLD. Accordingly, DLD activity, nicotinamide adenine dinucleotide hydrogen (NADH) levels, ATP levels and motility parameters were all restored to normal levels by Vc. Moreover, the effects of Vc on ameliorating these indicators had striking similarities to the effects of ethylenediaminetetraacetic acid (EDTA). In addition, neither the antioxidant melatonin nor the universal oxidant H₂O₂ influenced the tyrosine phosphorylation of DLD. Hence, the protective effects of Vc on the tyrosine phosphorylation of DLD might be attributed to its binding to Cd ions outside or inside sperm, and were not due to its antioxidant properties.

Actin cytoskeleton and sperm function

For the acquisition of the ability to fertilize the egg, mammalian spermatozoa should undergo a series of biochemical transformations in the female reproductive tract, collectively called capacitation. The capacitated sperm can undergo the acrosomal exocytosis process near or on the oocyte, which allows the spermatozoon to penetrate and fertilize it. One of the main processes in capacitation involves dynamic cytoskeletal remodeling particularly of actin. Actin polymerization occurs during sperm capacitation and the produced F-actin should be depolymerized prior to the acrosomal exocytosis. In the present review, we describe the mechanisms that regulate F-actin formation during sperm capacitation and the F-actin dispersion prior to the acrosomal exocytosis. During sperm capacitation, the actin severing proteins gelsolin and cofilin are inactive and they undergo activation prior to the acrosomal exocytosis.

Human antibodies to the dengue virus E-dimer epitope have therapeutic activity against Zika virus infection

The Zika virus (ZIKV) epidemic has resulted in congenital abnormalities in fetuses and neonates. Although some cross-reactive dengue virus (DENV)-specific antibodies can enhance ZIKV infection in mice, those recognizing the DENV E-dimer epitope (EDE) can neutralize ZIKV infection in cell culture. We evaluated the therapeutic activity of human monoclonal antibodies to DENV EDE for their ability to control ZIKV infection in the brains, testes, placentas, and fetuses of mice. A single dose of the EDE1-B10 antibody given 3 d after ZIKV infection protected against lethality, reduced ZIKV levels in brains and testes, and preserved sperm counts. In pregnant mice, wild-type or engineered LALA variants of EDE1-B10, which cannot engage Fcg receptors, diminished ZIKV burden in maternal and fetal tissues, and protected against fetal demise. Because neutralizing antibodies to EDE have therapeutic potential against ZIKV, in addition to their established inhibitory effects against DENV, it may be possible to develop therapies that control disease caused by both viruses.

Elevated aminopeptidase N affects sperm motility and early embryo development

Aminopeptidase N (APN) is a naturally occurring ectopeptidase present in mammalian semen. Previous studies have demonstrated that APN adversely affects male fertility through the alteration of sperm motility. This enzyme constitutes 0.5 to 1% of the seminal plasma proteins, which can be transferred from the prostasomes to sperms by a fusion process. In the present study, we investigated the molecular mechanism of action of APN and its role in regulating sperm functions and male fertility. In this in vitro study, epididymal mouse spermatozoa were incubated in a capacitating media (pH 7) containing 20 ng/mL of recombinant mouse APN for 90 min. Our results demonstrated that the supplementation of recombinant APN in sperm culture medium significantly increased APN activity, and subsequently altered motility, hyperactivated motility, rapid and medium swimming speeds, viability, and the acrosome reaction of mouse spermatozoa. These effects were potentially caused by increased toxicity in the spermatozoa. Further, altered APN activity in sperm culture medium affected early embryonic development. Interestingly, the effect of elevated APN activity in sperm culture medium was independent of protein tyrosine phosphorylation and protein kinase A activity. On the basis of these results, we concluded that APN plays a significant role in the regulation of several sperm functions and early embryonic development. In addition, increased APN activity could potentially lead to several adverse consequences related to male fertility.

Male Infertility Is Responsible for Nearly Half of the Extinction Observed in the Mouse Collaborative Cross

The goal of the Collaborative Cross (CC) project was to generate and distribute over 1000 independent mouse recombinant inbred strains derived from eight inbred founders. With inbreeding nearly complete, we estimated the extinction rate among CC lines at a remarkable 95%, which is substantially higher than in the derivation of other mouse recombinant inbred populations. Here, we report genome-wide allele frequencies in 347 extinct CC lines. Contrary to expectations, autosomes had equal allelic contributions from the eight founders, but chromosome X had significantly lower allelic contributions from the two inbred founders with underrepresented subspecific origins (PWK/PhJ and CAST/EiJ). By comparing extinct CC lines to living CC strains, we conclude that a complex genetic architecture is driving extinction, and selection pressures are different on the autosomes and chromosome X Male infertility played a large role in extinction as 47% of extinct lines had males that were infertile. Males from extinct lines had high variability in reproductive organ size, low sperm counts, low sperm motility, and a high rate of vacuolization of seminiferous tubules. We performed QTL mapping and identified nine genomic regions associated with male fertility and reproductive phenotypes. Many of the allelic effects in the QTL were driven by the two founders with underrepresented subspecific origins, including a QTL on chromosome X for infertility that was driven by the PWK/PhJ haplotype. We also performed the first example of cross validation using complementary CC resources to verify the effect of sperm curvilinear velocity from the PWK/PhJ haplotype on chromosome 2 in an independent population across multiple generations. While selection typically constrains the examination of reproductive traits toward the more fertile alleles, the CC extinct lines provided a unique opportunity to study the genetic architecture of fertility in a widely genetically variable population. We hypothesize that incompatibilities between alleles with different subspecific origins is a key driver of infertility. These results help clarify the factors that drove strain extinction in the CC, reveal the genetic regions associated with poor fertility in the CC, and serve as a resource to further study mammalian infertility.

Simple agarose micro-confinement array and machine-learning-based classification for analyzing the patterned differentiation of mesenchymal stem cells

The geometrical confinement of small cell colonies gives differential cues to cells sitting at the periphery versus the core. To utilize this effect, for example to create spatially graded differentiation patterns of human mesenchymal stem cells (hMSCs) in vitro or to investigate underpinning mechanisms, the confinement needs to be robust for extended time periods. To create highly repeatable micro-fabricated structures for cellular patterning and high-throughput data mining, we employed here a simple casting method to fabricate more than 800 adhesive patches confined by agarose micro-walls. In addition, a machine learning based image processing software was developed (open code) to detect the differentiation patterns of the population of hMSCs automatically. Utilizing the agarose walls, the circular patterns of hMSCs were successfully maintained throughout 15 days of cell culture. After staining lipid droplets and alkaline phosphatase as the markers of adipogenic and osteogenic differentiation, respectively, the mega-pixels of RGB color images of hMSCs were processed by the software on a laptop PC within several minutes. The image analysis successfully showed that hMSCs sitting on the more central versus peripheral sections of the adhesive circles showed adipogenic versus osteogenic differentiation as reported previously, indicating the compatibility of patterned agarose walls to conventional microcontact printing. In addition, we found a considerable fraction of undifferentiated cells which are preferentially located at the peripheral part of the adhesive circles, even in differentiation-inducing culture media. In this study, we thus successfully demonstrated a simple framework for analyzing the patterned differentiation of hMSCs in confined microenvironments, which has a range of applications in biology, including stem cell biology.

Beneficial effects of quercetin on titanium dioxide nanoparticles induced spermatogenesis defects in mice

Many recent studies have demonstrated that most nanoparticles (NPs) have an adverse or toxic action on male germ cells. In present study, protective effect of quercetin (Que) on titanium dioxide nanoparticle (NTiO₂)-induced spermatogenesis defects in mice was investigated. Thirty-two Naval Medical Research Institute (NMRI) mice were randomly divided into four groups. Que group received 75 mg/kg of Que for 42 days. NTiO₂ group received 300 mg/kg NTiO₂ for 35 days. NTiO₂ + Que group initially received 75 mg/kg Que for 7 days and was followed by concomitant administration of 300 mg/kg NTiO₂ for 35 days. Control group received only normal saline for 42 days. Sperm parameters, testosterone concentration, histological criteria, and apoptotic index were assessed. Product of lipid peroxidation (MDA), superoxide dismutase (SOD), and catalase (CAT) activities were also evaluated for oxidative stress in testicular tissue. Administration of NTiO₂ significantly induced histological changes in testicular tissue; increased apoptotic index; and decreased testicular weight, testosterone concentration, and sperm quality (p < 0.01). In the testis, NTiO₂ increased oxidative stress through an increase in lipid peroxidation and a decrease in SOD and CAT activities (p < 0.05). Que pretreatment could significantly attenuate testicular weight; apoptotic index; and histological criteria including vacuolization, detachment, and sloughing of germ cells in seminiferous tubules. Serum and tissue testosterone levels were significantly increased in Que-pretreated mice (p < 0.01). Sperm parameters including sperm number, motility, and percentage of abnormality were also effectively improved by Que pretreatment (p < 0.01). Pretreatment of Que significantly ameliorated oxidative stress and increased the activities of SOD and CAT in testicular tissue. These results indicate that sperm production can be increased by Que pretreatment in NTiO₂-intoxicated mice. The improved sperm quality and reverse testis histology by Que pretreatment may be a consequence of elevation testosterone concentration, reduction in germ cell apoptosis, and suppression of oxidative stress in testicular tissue.

Applying data mining techniques for increasing implantation rate by selecting best sperms for intra-cytoplasmic sperm injection treatment

BACKGROUND AND OBJECTIVE

Aspiration of a good-quality sperm during intracytoplasmic sperm injection (ICSI) is one of the main concerns. Understanding the influence of individual sperm morphology on fertilization, embryo quality, and pregnancy probability is one of the most important subjects in male factor infertility. Embryologists need to decide the best sperm for injection in real time during ICSI cycle. Our objective is to predict the quality of zygote, embryo, and implantation outcome before injection of each sperm in an ICSI cycle for male factor infertility with the aim of providing a decision support system on the sperm selection.

METHODS

The information was collected from 219 patients with male factor infertility at the infertility therapy center of Alzahra hospital in Rasht from 2012 through 2014. The prepared dataset included the quality of zygote, embryo, and implantation outcome of 1544 injected sperms into the related oocytes. In our study, embryo transfer was performed at day 3. Each sperm was represented with thirteen clinical features. Data preprocessing was the first step in the proposed data mining algorithm. After applying more than 30 classifiers, 9 successful classifiers were selected and evaluated by 10-fold cross validation technique using precision, recall, F1, and AUC measures. Another important experiment was measuring the effect of each feature in prediction process.

RESULTS

In zygote and embryo quality prediction, IBK and RandomCommittee models provided 79.2% and 83.8% F1, respectively. In implantation outcome prediction, KStar model achieved 95.9% F1, which is even better than prediction of human experts. All these predictions can be done in real time.

CONCLUSIONS

A machine learning-based decision support system would be helpful in sperm selection phase of ICSI cycle to improve the success rate of ICSI treatment.

Zika virus infection damages the testes in mice

Infection of pregnant women with Zika virus (ZIKV) can cause congenital malformations including microcephaly, which has focused global attention on this emerging pathogen. In addition to transmission by mosquitoes, ZIKV can be detected in the seminal fluid of affected males for extended periods of time and transmitted sexually. Here, using a mouse-adapted African ZIKV strain (Dakar 41519), we evaluated the consequences of infection in the male reproductive tract of mice. We observed persistence of ZIKV, but not the closely related dengue virus (DENV), in the testis and epididymis of male mice, and this was associated with tissue injury that caused diminished testosterone and inhibin B levels and oligospermia. ZIKV preferentially infected spermatogonia, primary spermatocytes and Sertoli cells in the testis, resulting in cell death and destruction of the seminiferous tubules. Less damage was caused by a contemporary Asian ZIKV strain (H/PF/2013), in part because this virus replicates less efficiently in mice. The extent to which these observations in mice translate to humans remains unclear, but longitudinal studies of sperm function and viability in ZIKV-infected humans seem warranted.

CABYR is essential for fibrous sheath integrity and progressive motility in mouse spermatozoa

Ca²⁺-binding tyrosine-phosphorylation-regulated protein (CABYR) has been implicated in sperm physiological function in several in vitro studies. It has also been implicated as a potential cause of and diagnostic tool in asthenozoospermic human males. CABYR is known to be localized to the fibrous sheath, an accessory structure in the flagellar principal piece. Utilizing the CRISPR-Cas9 technology, we have knocked out this gene in mice to understand its role in male fertility. Cabyr-knockout male mice showed severe subfertility with a defect in sperm motility as well as a significant disorganization in the fibrous sheath. Further, abnormal configuration of doublet microtubules was observed in the Cabyr-knockout spermatozoa, suggesting that the fibrous sheath is important for the correct organization of the axoneme. Our results show that it is the role of CABYR in the formation of the fibrous sheath that is essential for male fertility.

Transient exposure to calcium ionophore enables in vitro fertilization in sterile mouse models

Mammalian sperm acquire fertilizing capacity in the female tract in a process called capacitation. At the molecular level, capacitation requires protein kinase A activation, changes in membrane potential and an increase in intracellular calcium. Inhibition of these pathways results in loss of fertilizing ability in vivo and in vitro. We demonstrated that transient incubation of mouse sperm with Ca²⁺ ionophore accelerated capacitation and rescued fertilizing capacity in sperm with inactivated PKA function. We now show that a pulse of Ca²⁺ ionophore induces fertilizing capacity in sperm from infertile CatSper1 (Ca²⁺ channel), Adcy10 (soluble adenylyl cyclase) and Slo3 (K⁺ channel) KO mice. In contrast, sperm from infertile mice lacking the Ca²⁺ efflux pump PMACA4 were not rescued. These results indicate that a transient increase in intracellular Ca²⁺ can overcome genetic infertility in mice and suggest this approach may prove adaptable to rescue sperm function in certain cases of human male infertility.

Impact of arsenic(V) on testicular oxidative stress and sperm functional attributes in Swiss albino mice

The arsenic (As) is a multi system effector including reproduction. The present study examined the association of graded doses of As(V) on testicular microenvironment and sperm function in mice. Thirty-six adult male mice were randomly assigned to six groups (n = 6). Group A served as control without test chemical. The groups B, C, D, E, and F were administered graded doses of 10, 25, 50, 100, and 200 ppm As(V), respectively, through drinking water for 40 days. A dose-dependant significant (P < 0.05) decrements were observed in epididymal sperm kinematic attributes (progressive motility, rapid, fast progressive, VCL, VSL, VAP, LIN, STR, WOB and TYPE A (STR >80 %, ALH 2.5 μm) by CASA), viability, plasma membrane functional integrity, and mitochondrial membrane potential which were associated with insignificant decrease in serum testosterone levels. The histoarchitectural studies of testes showed progressive loss of spermatozoa concentration in the seminiferous tubules as the As(V) dose increased. The mice exposed to As(V) had an increase in the As accumulation, protein carbonylation, and lipid peroxidation levels associated with alterations in SOD, CAT, and GST activities in the testes. In conclusion, higher doses of As(V) (more than 50 ppm) were found to be testicular toxicants which impaired semen quality by inducing oxidative stress in the testicular microenvironment.

Paternal exposure to cigarette smoke condensate leads to reproductive sequelae and developmental abnormalities in the offspring of mice

Paternal smoking is associated with infertility, birth defects and childhood cancers. Our earlier studies using cigarette smoke condensate (CSC) demonstrated several deleterious changes in male germ cells. Here, we hypothesize that chronic paternal exposure to CSC causes molecular and phenotypic changes in the sire and the offspring, respectively. In this mouse study, CSC caused DNA damage and cytotoxicity in testes via accumulation of benzo(a)pyrene (B[a]P) and cotinine. Decreased expression of growth arrest and DNA damage inducible alpha (Gadd45a), aryl hydrocarbon receptor (Ahr), and cyclin-dependent kinase inhibitor 1A (P21) was seen in CSC exposed testes. Apoptotic germ cell death was detected by induction of Fas, FasL, and activated caspase-3. The CSC-exposed males displayed reduction in sperm motility and fertilizing ability and sired pups with reduced body weight and crown-rump length, and smaller litter size with higher numbers of resorption. This model of CSC exposure demonstrates testicular toxicity and developmental defects in the offspring.

Meiotic drive changes sperm precedence patterns in house mice: potential for male alternative mating tactics?

BACKGROUND

With female multiple mating (polyandry), male-male competition extends to after copulation (sperm competition). Males respond to this selective pressure through physiological, morphological and behavioural adaptations. Sperm competitiveness is commonly decreased in heterozygote carriers of male meiotic drivers, selfish genetic elements that manipulate the production of gametes in males. This might give carriers an evolutionary incentive to reduce the risk of sperm competition. Here, we explore this possibility in house mice. Natural populations frequently harbour a well-characterised male driver (t haplotype), which is transmitted to 90 % of heterozygous (+/t) males' offspring. Previous research demonstrated strong detrimental effects on sperm competitiveness, and suggested that +/t males are particularly disadvantaged against wild type males when first-to-mate. Low paternity success in the first-to-mate role is expected to favour male adaptations that decrease the risk of sperm competition by preventing female remating. Genotype-specific paternity patterns (sperm precedence) could lead to genetically determined alternative reproductive tactics that can spread through gene level selection. Here, we seek confirmation that +/t males are generally disadvantaged when first-to-mate and address whether males of different genotypes differ in reproductive tactics (copulatory and morphological) to maximise individual or driver fitness. Finally, we attempt to explain the mechanistic basis for alternative sperm precedence patterns in this species.

RESULTS

We confirmed that +/t males are weak sperm competitors when first to mate. When two +/t males competed, the second-to-mate was more successful, which contrasts with first male sperm precedence when wild type males competed. However, we found no differences between male genotypes in reproductive behaviour or morphology that were consistent with alternative reproductive tactics. Sperm of +/+ and +/t males differed with respect to in vitro sperm features. Premature hypermotility in +/t males' sperm can potentially explain why +/t males are very weak sperm competitors when first-to-mate.

CONCLUSIONS

Our results demonstrate that meiotic drivers can have strong effects on sperm precedence patterns, and may provide a heritable basis for alternative reproductive tactics motivated by reduced sperm competitiveness. We discuss how experimental and evolutionary constraints may help explain why male genotypes did not show the predicted differences.

Tyrosine phosphorylation of dihydrolipoamide dehydrogenase as a potential cadmium target and its inhibitory role in regulating mouse sperm motility

Cadmium (Cd) is reported to reduce sperm motility and functions. However, the molecular mechanisms of Cd-induced toxicity remain largely unknown, presenting a major knowledge gap in research on reproductive toxicology. In the present study, we identified a candidate protein, dihydrolipoamide dehydrogenase (DLD), which is a post-pyruvate metabolic enzyme, exhibiting tyrosine phosphorylation in mouse sperm exposed to Cd both in vivo and in vitro. Immunoprecipitation assay demonstrated DLD was phosphorylated in tyrosine residues without altered expression after Cd treatment, which further confirmed our identified result. However, the tyrosine phosphorylation of DLD did not participate in mouse sperm capacitation and Bovine Serum Albumin (BSA) effectively prevented the tyrosine phosphorylation of DLD. Moreover, Cd-induced tyrosine phosphorylation of DLD lowered its dehydrogenase activity and meanwhile, Nicotinamide Adenine Dinucleotide Hydrogen (NADH) content, Adenosine Triphosphate (ATP) production and sperm motility were all inhibited by Cd. Interestingly, when the tyrosine phosphorylation of DLD was blocked by BSA, the decrease of DLD activity, NADH and ATP content as well as sperm motility was also suppressed simultaneously. These results suggested that Cd-induced tyrosine phosphorylation of DLD inhibited its activity and thus suppressed the tricarboxylic acid (TCA) cycle, which resulted in the reduction of NADH and hence the ATP production generated through oxidative phosphorylation (OPHOXS). Taken together, our results revealed that Cd induced DLD tyrosine phosphorylation, in response to regulate TCA metabolic pathway, which reduced ATP levels and these negative effects led to decreased sperm motility. This study provided new understanding of the mechanisms contributing to the harmful effects of Cd on the motility and function of spermatozoa.

Structural analyses to identify selective inhibitors of glyceraldehyde 3-phosphate dehydrogenase-S, a sperm-specific glycolytic enzyme

STUDY HYPOTHESIS

Detailed structural comparisons of sperm-specific glyceraldehyde 3-phosphate dehydrogenase, spermatogenic (GAPDHS) and the somatic glyceraldehyde 3-phosphate dehydrogenase (GAPDH) isozyme should facilitate the identification of selective GAPDHS inhibitors for contraceptive development.

STUDY FINDING

This study identified a small-molecule GAPDHS inhibitor with micromolar potency and >10-fold selectivity that exerts the expected inhibitory effects on sperm glycolysis and motility.

WHAT IS KNOWN ALREADY

Glycolytic ATP production is required for sperm motility and male fertility in many mammalian species. Selective inhibition of GAPDHS, one of the glycolytic isozymes with restricted expression during spermatogenesis, is a potential strategy for the development of a non-hormonal contraceptive that directly blocks sperm function.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

Homology modeling and x-ray crystallography were used to identify structural features that are conserved in GAPDHS orthologs in mouse and human sperm, but distinct from the GAPDH orthologs present in somatic tissues. We identified three binding pockets surrounding the substrate and cofactor in these isozymes and conducted a virtual screen to identify small-molecule compounds predicted to bind more tightly to GAPDHS than to GAPDH. Following the production of recombinant human and mouse GAPDHS, candidate compounds were tested in dose-response enzyme assays to identify inhibitors that blocked the activity of GAPDHS more effectively than GAPDH. The effects of a selective inhibitor on the motility of mouse and human sperm were monitored by computer-assisted sperm analysis, and sperm lactate production was measured to assess inhibition of glycolysis in the target cell.

MAIN RESULTS AND THE ROLE OF CHANCE

Our studies produced the first apoenzyme crystal structures for human and mouse GAPDHS and a 1.73 Å crystal structure for NAD(+)-bound human GAPDHS, facilitating the identification of unique structural features of this sperm isozyme. In dose-response assays T0501_7749 inhibited human GAPDHS with an IC50 of 1.2 μM compared with an IC50 of 38.5 μM for the somatic isozyme. This compound caused significant reductions in mouse sperm lactate production (P= 0.017 for 100 μM T0501_7749 versus control) and in the percentage of motile mouse and human sperm (P values from <0.05 to <0.0001, depending on incubation conditions).

LIMITATIONS, REASONS FOR CAUTION

The chemical properties of T0501_7749, including limited solubility and nonspecific protein binding, are not optimal for drug development.

WIDER IMPLICATIONS OF THE FINDINGS

This study provides proof-of-principle evidence that GAPDHS can be selectively inhibited, causing significant reductions in sperm glycolysis and motility. These results highlight the utility of structure-based drug design and support further exploration of GAPDHS, and perhaps other sperm-specific isozymes in the glycolytic pathway, as contraceptive targets.

LARGE SCALE DATA

None. Coordinates and data files for three GAPDHS crystal structures were deposited in the RCSB Protein Data Bank (http://www.rcsb.org).

STUDY FUNDING AND COMPETING INTERESTS

This work was supported by grants from the National Institutes of Health (NIH), USA, including U01 HD060481 and cooperative agreement U54 HD35041 as part of the Specialized Cooperative Centers Program in Reproduction and Infertility Research from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, and TW/HD00627 from the NIH Fogarty International Center. Additional support was provided by subproject CIG-05-109 from CICCR, a program of CONRAD, Eastern Virginia Medical School, USA. There are no conflicts of interest.

The tyrosine kinase FER is responsible for the capacitation-associated increase in tyrosine phosphorylation in murine sperm

Sperm capacitation is required for fertilization. At the molecular level, this process is associated with fast activation of protein kinase A. Downstream of this event, capacitating conditions lead to an increase in tyrosine phosphorylation. The identity of the tyrosine kinase(s) mediating this process has not been conclusively demonstrated. Recent experiments using stallion and human sperm have suggested a role for PYK2 based on the use of small molecule inhibitors directed against this kinase. However, crucially, loss-of-function experiments have not been reported. Here, we used both pharmacological inhibitors and genetically modified mice models to investigate the identity of the tyrosine kinase(s) mediating the increase in tyrosine phosphorylation in mouse sperm. Similar to stallion and human, PF431396 blocks the capacitation-associated increase in tyrosine phosphorylation. Yet, sperm from Pyk2(-/-) mice displayed a normal increase in tyrosine phosphorylation, implying that PYK2 is not responsible for this phosphorylation process. Here, we show that PF431396 can also inhibit FER, a tyrosine kinase known to be present in sperm. Sperm from mice targeted with a kinase-inactivating mutation in Fer failed to undergo capacitation-associated increases in tyrosine phosphorylation. Although these mice are fertile, their sperm displayed a reduced ability to fertilize metaphase II-arrested eggs in vitro.

Cadmium inhibits mouse sperm motility through inducing tyrosine phosphorylation in a specific subset of proteins

Cadmium (Cd) has been reported to impair male fertility, primarily by disrupting sperm motility, but the underlying molecular mechanism remains unclear. Here we investigated the effects of Cd on sperm motility, tyrosine phosphorylation, AMP-activated protein kinase (AMPK) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity, and ATP levels in vitro. Our results demonstrated that Cd inhibited sperm motility, GAPDH activity, AMPK activity and ATP production, and induced tyrosine phosphorylation of 55-57KDa proteins. Importantly, all the parameters affected by Cd were restored to normal levels when incubated with 10μM Cd in the presence of 30μM ethylene diamine tetraacetic acid (EDTA). Interestingly, changes of tyrosine phosphorylation levels of 55-57KDa proteins are completely contrary to that of other parameters. These results suggest that Cd-induced tyrosine phosphorylation of 55-57KDa proteins might act as an engine to block intracellular energy metabolism and thus decrease sperm motility.

The effect of friction and impact angle on the spermatozoa-oocyte local contact dynamics

Although a large proportion of biomolecules involved in spermatozoa-oocyte interaction has been discovered so far, many details of fertilization mechanism remain unknown. Both biochemical and biomechanical components exist in the fertilization process. Mammalian sperm evolved a ZP (zona pelucida) thrust reduction penetration strategy probably in response to the ZP resilient elasticity. Using a biomechanical approach and FEM analysis, local contact stress, ZP deformations during impact and attempt of sperm head penetration relative to different sperm impact angles (SIA) were studied. The sperm-oocyte contact was defined as non-linear frictional contact. A transient structural analysis at 37°C revealed that, from the mechanical standpoint there are SIA that are more favorable for possible ZP penetration due to larger equivalent stress of ZP. An "slip-stick" resembling effect was identified for almost all examined SIA. The sperm head-ZP contact area increases as SIA decreases. Favorable ZP-stress state for sperm penetration regarding SIA are discussed.

Cryorecovery of Mouse Sperm by Different IVF Methods Using MBCD and GSH

Different protocols incorporating methyl-β-cyclodextrin (MBCD) and reduced glutathione (GSH) have been reported to improve IVF recovery of cryopreserved mouse sperm on a C57BL/6 (J and N) genetic background. However, it is not clear which IVF protocol is most appropriate when using the various methods to cryorecover sperm with different sperm quality and sample volumes. Therefore, in the present study we correlated sperm motility with fertilization rate and compared the efficiency of different IVF methods using various sperm samples so as to establish general guidelines for mouse sperm cryorecovery by IVF. High linear correlation between sperm fertilization rate and progressive motility was found, R² was 0.9623 and 0.9993 for pre-freezing and post-thaw progressive motility, respectively. High amounts of cryoprotective agent (CPA) were observed to impair both sperm capacitation and fertilization. Moreover, the presence of a large number of immotile sperm in the sperm-oocyte co-incubation drop was found to reduce IVF success which could be partially reversed by supplementation using monothioglycerol (MTG) during centrifugation. It was concluded that the efficiency of IVF using cryorecovered mouse sperm in media containing MBCD and GSH can be predicted from sperm progressive motility. High concentrations of CPA and immotile sperm should be mitigated prior to IVF. The optimum IVF method should be selected based on sperm sample volume and sperm parameters.

Autophagy is required for ectoplasmic specialization assembly in sertoli cells

The ectoplasmic specialization (ES) is essential for Sertoli-germ cell communication to support all phases of germ cell development and maturity. Its formation and remodeling requires rapid reorganization of the cytoskeleton. However, the molecular mechanism underlying the regulation of ES assembly is still largely unknown. Here, we show that Sertoli cell-specific disruption of autophagy influenced male mouse fertility due to the resulting disorganized seminiferous tubules and spermatozoa with malformed heads. In autophagy-deficient mouse testes, cytoskeleton structures were disordered and ES assembly was disrupted. The disorganization of the cytoskeleton structures might be caused by the accumulation of a negative cytoskeleton organization regulator, PDLIM1, and these defects could be partially rescued by Pdlim1 knockdown in autophagy-deficient Sertoli cells. Altogether, our works reveal that the degradation of PDLIM1 by autophagy in Sertoli cells is important for the proper assembly of the ES, and these findings define a novel role for autophagy in Sertoli cell-germ cell communication.

The Founder Strains of the Collaborative Cross Express a Complex Combination of Advantageous and Deleterious Traits for Male Reproduction

Surveys of inbred strains of mice are standard approaches to determine the heritability and range of phenotypic variation for biomedical traits. In addition, they may lead to the identification of novel phenotypes and models of human disease. Surprisingly, male reproductive phenotypes are among the least-represented traits in the Mouse Phenome Database. Here we report the results of a broad survey of the eight founder inbred strains of both the Collaborative Cross (CC) and the Diversity Outbred populations, two new mouse resources that are being used as platforms for systems genetics and sources of mouse models of human diseases. Our survey includes representatives of the three main subspecies of the house mice and a mix of classical and wild-derived inbred strains. In addition to standard staples of male reproductive phenotyping such as reproductive organ weights, sperm counts, and sperm morphology, our survey includes sperm motility and the first detailed survey of testis histology. As expected for such a broad survey, heritability varies widely among traits. We conclude that although all eight inbred strains are fertile, most display a mix of advantageous and deleterious male reproductive traits. The CAST/EiJ strain is an outlier, with an unusual combination of deleterious male reproductive traits including low sperm counts, high levels of morphologically abnormal sperm, and poor motility. In contrast, sperm from the PWK/PhJ and WSB/EiJ strains had the greatest percentages of normal morphology and vigorous motility. Finally, we report an abnormal testis phenotype that is highly heritable and restricted to the WSB/EiJ strain. This phenotype is characterized by the presence of a large, but variable, number of vacuoles in at least 10% of the seminiferous tubules. The onset of the phenotype between 2 and 3 wk of age is temporally correlated with the formation of the blood-testis barrier. We speculate that this phenotype may play a role in high rates of extinction in the CC project and in the phenotypes associated with speciation in genetic crosses that use the WSB/EiJ strain as representative of the Mus muculus domesticus subspecies.

CRISPR/Cas9-Mediated Rapid Generation of Multiple Mouse Lines Identified Ccdc63 as Essential for Spermiogenesis

Spermatozoa are flagellated cells whose role in fertilization is dependent on their ability to move towards an oocyte. The structure of the sperm flagella is highly conserved across species, and much of what is known about this structure is derived from studies utilizing animal models. One group of proteins essential for the movement of the flagella are the dyneins. Using the advanced technology of CRISPR/Cas9 we have targeted three dynein group members; Dnaic1, Wdr63 and Ccdc63 in mice. All three of these genes are expressed strongly in the testis. We generated mice with amino acid substitutions in Dnaic1 to analyze two specific phosphorylation events at S124 and S127, and generated simple knockouts of Wdr63 and Ccdc63. We found that the targeted phosphorylation sites in Dnaic1 were not essential for male fertility. Similarly, Wdr63 was not essential for male fertility; however, Ccdc63 removal resulted in sterile male mice due to shortened flagella. This study demonstrates the versatility of the CRISPR/Cas9 system to generate animal models of a highly complex system by introducing point mutations and simple knockouts in a fast and efficient manner.

Biphasic role of calcium in mouse sperm capacitation signaling pathways

Mammalian sperm acquire fertilizing ability in the female tract in a process known as capacitation. At the molecular level, capacitation is associated with up-regulation of a cAMP-dependent pathway, changes in intracellular pH, intracellular Ca(2+), and an increase in tyrosine phosphorylation. How these signaling systems interact during capacitation is not well understood. Results presented in this study indicate that Ca(2+) ions have a biphasic role in the regulation of cAMP-dependent signaling. Media without added Ca(2+) salts (nominal zero Ca(2+)) still contain micromolar concentrations of this ion. Sperm incubated in this medium did not undergo PKA activation or the increase in tyrosine phosphorylation suggesting that these phosphorylation pathways require Ca(2+). However, chelation of the extracellular Ca(2+) traces by EGTA induced both cAMP-dependent phosphorylation and the increase in tyrosine phosphorylation. The EGTA effect in nominal zero Ca(2+) media was mimicked by two calmodulin antagonists, W7 and calmidazolium, and by the calcineurin inhibitor cyclosporine A. These results suggest that Ca(2+) ions regulate sperm cAMP and tyrosine phosphorylation pathways in a biphasic manner and that some of its effects are mediated by calmodulin. Interestingly, contrary to wild-type mouse sperm, sperm from CatSper1 KO mice underwent PKA activation and an increase in tyrosine phosphorylation upon incubation in nominal zero Ca(2+) media. Therefore, sperm lacking Catsper Ca(2+) channels behave as wild-type sperm incubated in the presence of EGTA. This latter result suggests that Catsper transports the Ca(2+) involved in the regulation of cAMP-dependent and tyrosine phosphorylation pathways required for sperm capacitation.

Flow cytometry analysis reveals that only a subpopulation of mouse sperm undergoes hyperpolarization during capacitation

To gain fertilizing capacity, mammalian sperm should reside in the female tract for a period of time. The physiological changes that render the sperm able to fertilize are known as capacitation. Capacitation is associated with an increase in intracellular pH, an increase in intracellular calcium, and phosphorylation of different proteins. This process is also accompanied by the hyperpolarization of the sperm plasma membrane potential (Em). In the present work, we used flow cytometry to analyze changes in sperm Em during capacitation in individual cells. Our results indicate that a subpopulation of hyperpolarized mouse sperm can be clearly distinguished by sperm flow cytometry analysis. Using sperm bearing green fluorescent protein in their acrosomes, we found that this hyperpolarized subpopulation is composed of sperm with intact acrosomes. In addition, we show that the capacitation-associated hyperpolarization is blocked by high extracellular K(+), by PKA inhibitors, and by SLO3 inhibitors in CD1 mouse sperm, and undetectable in Slo3 knockout mouse sperm. On the other hand, in sperm incubated in conditions that do not support capacitation, sperm membrane hyperpolarization can be induced by amiloride, high extracellular NaHCO3, and cAMP agonists. Altogether, our observations are consistent with a model in which sperm Em hyperpolarization is downstream of a cAMP-dependent pathway and is mediated by the activation of SLO3 K(+) channels.

Influence of sperm impact angle on successful fertilization through mZP oscillatory spherical net model

According to the available literature, penetrating sperm creates an oblique path trough Zona pellucida (ZP)--the most outer surface of oocytes. Considering fertilization process as an oscillatory phenomenon, the influence of sperm impact angle relative to the oscillatory behavior of mouse ZP is described by using the discrete continuum mechanical model in the form of a spherical net model. A parametric frequency analysis of oscillatory behavior of knot material particles in the mouse ZP (mZP) spherical net model is conducted by using generalized Lussajous curves. The influence of impact angles of sperm cells on the corresponding knot mass particles' resultant trajectory is discussed. Favorable sperm impact angles for successful fertilization are identified.

Spermatozoa from mice deficient in Niemann-Pick disease type C2 (NPC2) protein have defective cholesterol content and reduced in vitro fertilising ability

The cholesterol content of the sperm membrane is regulated during both maturation in the epididymis and capacitation in the female tract, two processes required for the spermatozoa to acquire their fertilising ability. Because Niemann-Pick disease, type C2 (NPC2) protein is one of the most abundant components of the epididymal fluid and contains a functional cholesterol-binding site that can transfer cholesterol between membranes, it has been suggested for years that NPC2 could be involved in the regulation of cholesterol levels in spermatozoa during epididymal maturation. In the present study, western blot and immunohistochemistry analyses demonstrated significant levels of NPC2 in the mouse epididymal epithelium. Epididymal spermatozoa obtained from NPC2(-/-) mice were morphologically normal and had normal motility parameters, but had a reduced cholesterol content compared with that of wild-type (WT) spermatozoa, as determined by both biochemical and by flow cytometry analyses. These results suggest that NPC2 could be involved in regulating cholesterol levels in spermatozoa during epididymal maturation. To understand the relevance of epididymal NPC2 for sperm function, the ability of spermatozoa to undergo events influenced by epididymal maturation, such as capacitation and fertilisation, were compared between WT and NPC2(-/-) mice. Capacitated NPC2(-/-) spermatozoa exhibited defective tyrosine phosphorylation patterns and a reduced ability to fertilise cumulus-oocyte complexes compared with WT spermatozoa, supporting the relevance of mouse epididymal NPC2 for male fertility.

Impaired sperm maturation in RNASE9 knockout mice

Ribonuclease, RNase A family, 9 (RNASE9) is a ribonuclease A superfamily member that is expressed only in the epididymis. It is a small, secreted polypeptide, it lacks ribonuclease activity, and its function(s) is unknown. However, epididymis-specific expression suggests a role in sperm maturation. We generated Rnase9(-/-) mice to study RNASE9 function in vivo. We confirm that RNASE9 expression is restricted to the epididymis. Within the epididymis, RNASE9 is first detected in midcaput, persists through the distal caput and corpus, and wanes in the cauda. Rnase9(-/-) mice are born at the expected Mendelian ratio, have normal postnatal growth and development, and have no outwardly apparent phenotype. Spermatogenesis is normal, and Rnase9-null sperm are morphologically normal. Rnase9(-/-) males have normal fertility in unrestricted mating trials, and fertilization rates in in vitro fertilization assays are indistinguishable from wild-type mice. Visual observations coupled with analyses of sperm velocities shortly after swim out from the corpus shows that motility of Rnase9-null sperm is significantly impaired. However, no differences between wild-type and Rnase9-null sperm are detected by computer-assisted sperm analysis 10-90 min after sperm isolation from the corpus or cauda. Assessment of capacitation-dependent signaling pathways in Rnase9-null sperm showed that, while levels of tyrosine phosphorylation of sperm proteins were normal, there was decreased phosphorylation of protein kinase A substrates upon capacitation compared to wild-type mice. In conclusion, RNASE9 is dispensable for fertility, but the absence of RNASE9 during epididymal transit results in impaired sperm maturation.