Sperm IZUMO1 Is Required for Binding Preceding Fusion With Oolemma in Mice and Rats

Fertilization occurs as the culmination of multi-step complex processes. First, mammalian spermatozoa undergo the acrosome reaction to become fusion-competent. Then, the acrosome-reacted spermatozoa penetrate the zona pellucida and adhere to and finally fuse with the egg plasma membrane. IZUMO1 is the first sperm protein proven to be essential for sperm-egg fusion in mammals, as Izumo1 knockout mouse spermatozoa adhere to but fail to fuse with the oolemma. However, the IZUMO1 function in other species remains largely unknown. Here, we generated Izumo1 knockout rats by CRISPR/Cas9 and found the male rats were infertile. Unlike in mice, Izumo1 knockout rat spermatozoa failed to bind to the oolemma. Further investigation revealed that the acrosome-intact sperm binding conceals a decreased number of the acrosome-reacted sperm bound to the oolemma in Izumo1 knockout mice. Of note, we could not see any apparent defects in the binding of the acrosome-reacted sperm to the oolemma in the mice lacking recently found fusion-indispensable genes, Fimp, Sof1, Spaca6, or Tmem95. Collectively, our data suggest that IZUMO1 is required for the sperm-oolemma binding prior to fusion at least in rat.

Relationship of motility and acrosome reaction on sexing sperm in Ongole Crossbred bull

Artificial insemination using sexing semen is expected to produce calves with the desired sex. One sexing sperm method is the percoll density gradient centrifugation method. This study aimed to determine the changes and the relationship between motility and acrosome reaction after sexing process using percoll density gradient centrifugation. The material used was semen of ±5 years old Ongole crossbred bull with a bodyweight of ±700 kg as many as three bulls with mass motility 2+ and individual motility 70%. The method used was to compare fresh semen with sexed semen after the cooling process. Parameters measured were motility characters using CASA analysis, which included motility parameters, progressive motility, capacitation, and no acrosome reaction. Statistical analysis used paired T-test to distinguish among fresh semen, after sexing and cooling process. In comparison, regression and correlation were used to analyze the relationship of capacitation and hyperactivation sperm with no acrosomal reaction with motility and progressive motility. The results showed that motility and progressive motility decreased after the sexing and cooling process. Meanwhile, the acrosomal reaction, capacitation, and hyperactivity increased.

The importance of bovine seminal plasma proteins in the sperm function and fertility

Bovine livestock is one of the most important economic and social sectors for many countries. In this sense, the development of strategies to improve reproductive bull fertility and reproduction rates is relevant. It's highlighted the role of seminal plasma proteins (SPP) in reproductive fertility, so it has found close relationships among studies on the structure and biological activity of SPP, with seminal quality, including viability, sperm motility, and morphology. In addition, they have been found to regulate sperm functions such as capacitation, acrosome reaction, and they are even related to protecting sperm against thermal and oxidative stress. Moreover, the methods of separation and protein identification and their contribution to characterizing the bovine SP proteome should be also highlighted. In this sense, the most recent studies have been directed towards developing supplements with SPP that improve quality sperm subjected to cryopreservation processes. Research has begun and should forward to establish how the networks or sets of proteins are related to the functioning and fertility of sperm, the search for biomarkers of fertility, and the use of proteins in biotechnological processes, to increase efficiency reproductive.

Localization and Distribution of Testicular Angiotensin I Converting Enzyme (ACE) in Neck and Mid-Piece of Spermatozoa from Infertile Men in Relation to Sperm Motility

Testicular angiotensin converting enzyme (ACE) is known to play an essential role in the male reproduction and fertility. Data about tACE in cases of male infertility are quite scarce, and in this respect we aimed to study localization and distribution of tACE protein in the neck and mid-piece of spermatozoa from pathological samples in relation to sperm motility. The enzyme expression during capacitation and acrosome reaction was quantitatively assessed. In human ejaculated spermatozoa tACE is localized on sperm plasma membrane of the head, the neck and mid-piece of the tail. The immunoreactivity becomes stronger in capacitated spermatozoa followed by a decrease in acrosome reacted sperm. In different cases of semen pathology (oligozoospermia, asthenozoospermia and teratozoospermia) fluorescent signals in the neck and mid-piece are in punctate manner whereas in normozoospermia they were uniformly distributed. The expression area of tACE the neck and mid-piece was decreased in ejaculated and capacitated sperm from pathological semen samples compared to normospermia. Significant positive correlation was established between tACE area and progressive sperm motility, whereas with immotile sperm the correlation was negative. Our data suggest that proper distribution of tACE in the neck and mid-piece is required for normal sperm motility that could be used as a novel biomarker for male infertility.

The effect of IBMX and prolactin on functional status of cryopreserved bull spermatozoa

Purpose: investigate the effect of IBMX (activator of protein phosphorylation) and prolactin (PRL) on the functional state of cryopreserved bovine spermatozoa using inhibitory analysis.Materials and methods. Frozen-thawed semen samples from 60 black-and-white bulls was used in the experiments. For capacitation, cells were incubated in Sp-TALP medium supplemented with 6 mg/ml bovine serum albumin and various compounds: an inductor of capacitation (IBMX at concentrations of 1 μM, 10 μM, 50 μM, 100 μM), hormone (PRL at concentrations of 1 ng, 10 ng, 50 ng, 100 ng) and inhibitors of protein kinases C (Ro 31-8220 at a concentration of 10 ng/ml) and protein kinase A (H-89 at a concentration of 10 μM). The incubation was carried out at 38°C in an atmosphere of 5% CO2, 98% humidity for 4 hours. The functional status of the cells was determined by the chlortetracycline test.Results. It was shown that IBMX at all experimental concentrations did not affect the post-ejaculatory maturation (capacitation and acrosome reaction) of spermatozoa, while all concentrations of PRL (1-100 ng/ml) promoted the acrosome reaction in capacitated cells. In the presence of a protein kinase A inhibitor, there was a decrease in number of capacitated and an increase in number of acrosome-reactive spermatozoa under the action of IBMX at a concentration of 100 μM and no changes under the action of a protein kinase C inhibitor. Also, in case of protein kinase C inhibition the PRL-related stimulation of the acrosome reaction was canceled, while the usage of H-89 did not affect the functional status of spermatozoa, mediated by PRL. Thus, the influence of IBMX and PRL on the processes of post-ejaculatory maturation in thawed bovine spermatozoa was studied using the inhibitory analysis.Conclusion. At the capacital stage, all studied IBMX concentrations did not affect the ratio of deconved cells with various functional status. Prode also contributed to the passage of the acrosomous reaction in the rolled spermatozoa after defrosting. Inhibition of protein kinase A when incubating cells with IBMX has mediated the processes of acrosomal exocytosis in ripped cells and did not affect this process under the action of the PRR, while the protein kinase inhibitor C changed the ratio of cells with various functional status in the direction of increasing the percentage of cells at the rate of occasion I did not participate in intracellular action provided IBMX on deconved cells.

Bovine Follicular Fluid Derived Extracellular Vesicles Modulate the Viability, Capacitation and Acrosome Reaction of Bull Spermatozoa

While follicular fluid (FF) is known to enhance the functional properties of spermatozoa, the role of FF-derived extracellular vesicles (EVs) in this respect is unknown. We hypothesized that bovine FF EVs convey signals to spermatozoa supporting sperm viability, inducing sperm capacitation and acrosome reaction. In this study, the effects of bovine FF EVs on sperm functions are evaluated. Irrespective of the size of the follicles which FF EVs had originated from, they were capable of supporting sperm viability, inducing capacitation and acrosome reaction. These effects were specific to the source of bovine FF EVs, as human-cell-line-derived or porcine FF EVs did not affect spermatozoa viability or induced capacitation and acrosome reaction. A minimum of 5 × 105 EVs/mL was adequate to maintain sperm viability and induce capacitation and acrosome reaction in spermatozoa. Interestingly, with FF EV trypsin treatment, FF EVs lost their ability to support sperm functions. In conclusion, this study demonstrates that bovine FF EVs can support spermatozoa function and may contribute to a favorable periconceptional microenvironment. This is an important aspect of the interactions between different sexes at the earliest stages of reproduction and helps to understand molecular mechanisms modulating processes such as sperm competition and female cryptic choice.

KCNQ1 Potassium Channel Expressed in Human Sperm Is Involved in Sperm Motility, Acrosome Reaction, Protein Tyrosine Phosphorylation, and Ion Homeostasis During Capacitation

Potassium channels are involved in membrane hyperpolarization and ion homeostasis regulation during human sperm capacitation. However, the types of potassium channels in human sperm remain controversial. The voltage-gated ion channel KCNQ1 is ubiquitously expressed and regulates key physiological processes in the human body. In the present study, we investigated whether KCNQ1 is expressed in human sperm and what role it might have in sperm function. The expression and localization of KCNQ1 in human sperm were evaluated using Western blotting and indirect immunofluorescence. During capacitation incubation, human sperm were treated with KCNQ1- specific inhibitor chromanol 293B. Sperm motility was analyzed using a computer-assisted sperm analyzer. The acrosome reaction was studied using fluorescein isothiocyanate-conjugated Pisum sativum agglutinin staining. Protein tyrosine phosphorylation levels and localization after capacitation were determined using Western blotting and immunofluorescence. Intracellular K+, Ca2+, Cl−, pH, and membrane potential were analyzed using fluorescent probes. The results demonstrate that KCNQ1 is expressed and localized in the head and tail regions of human sperm. KCNQ1 inhibition reduced sperm motility, acrosome reaction rates, and protein tyrosine phosphorylation but had no effect on hyperactivation. KCNQ1 inhibition also increased intracellular K+, membrane potential, and intracellular Cl−, while decreasing intracellular Ca2+ and pH. In conclusion, the KCNQ1 channel plays a crucial role during human sperm capacitation.

Recurrent Independent Pseudogenization Events of the Sperm Fertilization Gene ZP3r in Apes and Monkeys

In mice, ZP3r/sp56 is a binding partner to the egg coat protein ZP3 and may mediate induction of the acrosome reaction. ZP3r, as a member of the RCA cluster, is surrounded by paralogs, some of which have been shown to be evolving under positive selection. Sequence divergence paired with paralogous relationships with neighboring genes, has complicated the accurate identification of the human ZP3r ortholog. Here, we phylogenetically and syntenically resolve that the human ortholog of ZP3r is the pseudogene C4BPAP1. We investigate the evolution of this gene within primates. We observe independent pseudogenization events of ZP3r in all Apes with the exception of Orangutans, and many monkey species. ZP3r in both primates that retain ZP3r and rodents contains positively selected sites. We hypothesize that redundant mechanisms mediate ZP3 recognition in mammals and ZP3rs relative importance to ZP recognition varies across species.

Reassessment of the proteomic composition and function of extracellular vesicles in the seminal plasma

Seminal plasma contains a high concentration of extracellular vesicles (EVs). The heterogeneity of small EVs or the presence of non-vesicular extracellular matter (NV) pose major obstacles in understanding the composition and function of seminal EVs. In this study, we employed high-resolution density gradient fractionation to accurately characterize the composition and function of seminal EVs and NV. We found that the seminal EVs could be divided into three different subtypes, namely high-density EV (EV-H), medium-density EV (EV-M), and low-density EV (EV-L) after purification using iodixanol,while NV was successfully isolated. EVs and NV display different features in size, shape and expression of some classic exosome markers. Both EV-H and NV could markedly promote sperm motility and capacitation compared with EV-M and EV-L, whereas only the NV fraction induced sperm acrosome reaction. Proteomic analysis results showed that EV-H, EV-M, EV-L, and NV had different protein components and were involved in different physiological functions. Further study showed that EV-M might reduce the production of sperm intrinsic reactive oxygen species (ROS) through Glutathione S-transferase Mu 2 (GSTM2).This study provides novel insights into important aspects of seminal EVs constituents and sounder footing to explore their functional properties in male fertility.