sperm activation
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Sperm motility acquisition during maturation is essential for successful fertilization.Extracellular adenosine-5'-triphosphate (ATP) level mediation by MIG-23, which is a homolog of human ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase), was required for major sperm protein filament dynamics and sperm motility in the nematode Ascaris suum. MIG-23 was localized on the sperm plasma membrane. During sperm activation, mitochondrial activity was increased dramatically, and a large amount of ATP was produced and stored in refringent granules (RGs). In addition, a portion of the produced ATP was released to the extracellular space through ATP channels, which were composed of innexins and localized on the sperm plasma membrane. Spermatozoa, instead of spermatids, hydrolyzed exogenous ATP and processed ecto-ATPase activity. MIG-23 contributed to the ecto-ATPase activity of spermatozoa. MIG-23 activity was interrupted, spermatozoa also decreased their ATP hydrolysis activity. Blocking MIG-23 activity resulted in an increase in the depolymerization rate of MSP filaments in pseudopodia, which eventually affected nematode sperm migration. Overall, our data imply that MIG-23, which contributes to the ecto-ATPase activity of spermatozoa, regulates sperm migration by modulating extracellular ATP levels.

Abstract The sperm motility of fish reflects their fertilizing ability. Sperm activation in fish with external fertilization occurs in an isotonic medium (sea or freshwater). The duration of sperm motility is a compromise between the level of energy reserves possessed by the sperm and the process of osmotic damage it experiences in the activating medium. Under natural conditions, various biotic and abiotic factors can affect the characteristics of motility. At the same time, when assessing the reproductive potential of males in laboratory conditions, the dilution and methods of its activation have a significant effect on the characteristics of sperm quality (namely, speed, the proportion of motile spermatozoa, and the time of their activity). In our work, we determined the main characteristics of the motility of the Black Sea turbot sperm at a dilution of 1:10 and 1: 100 with seawater. We have shown that, the average speed and percentage of motile sperm significantly decrease with higher dilution of seawater.

In mammals, integrins are heterodimeric transmembrane glycoproteins that represent a large group of cell adhesion receptors involved in cell–cell, cell–extracellular matrix, and cell–pathogen interactions. Integrin receptors are an important part of signalization pathways and have an ability to transmit signals into and out of cells and participate in cell activation. In addition to somatic cells, integrins have also been detected on germ cells and are known to play a crucial role in complex gamete-specific physiological events, resulting in sperm-oocyte fusion. The main aim of this review is to summarize the current knowledge on integrins in reproduction and deliver novel perspectives and graphical interpretations presenting integrin subunits localization and their dynamic relocation during sperm maturation in comparison to the oocyte. A significant part of this review is devoted to discussing the existing view of the role of integrins during sperm migration through the female reproductive tract; oviductal reservoir formation; sperm maturation processes ensuing capacitation and the acrosome reaction, and their direct and indirect involvement in gamete membrane adhesion and fusion leading to fertilization.

The trace element zinc is essential for many aspects of physiology. The mitochondrion is a major Zn2+ store, and excessive mitochondrial Zn2+ is linked to neurodegeneration. How mitochondria maintain their Zn2+ homeostasis is unknown. Here, we find that the SLC-30A9 transporter localizes on mitochondria and is required for export of Zn2+ from mitochondria in both Caenorhabditis elegans and human cells. Loss of slc-30a9 leads to elevated Zn2+ levels in mitochondria, a severely swollen mitochondrial matrix in many tissues, compromised mitochondrial metabolic function, reductive stress, and induction of the mitochondrial stress response. SLC-30A9 is also essential for organismal fertility and sperm activation in C. elegans, during which Zn2+ exits from mitochondria and acts as an activation signal. In slc-30a9–deficient neurons, misshapen mitochondria show reduced distribution in axons and dendrites, providing a potential mechanism for the Birk–Landau–Perez cerebrorenal syndrome where an SLC30A9 mutation was found.

Abstract To acquire and maintain directed cell motility, Caenorhabditis elegans sperm must undergo extensive, regulated cellular remodeling, in the absence of new transcription or translation. To regulate sperm function, nematode sperm employ large numbers of protein kinases and phosphatases, including SPE-6, a member of C. elegans’ highly expanded casein kinase 1 superfamily. SPE-6 functions during multiple steps of spermatogenesis, including functioning as a “brake” to prevent premature sperm activation in the absence of normal extracellular signals. Here we describe the sub-cellular localization patterns of SPE-6 during wildtype C. elegans sperm development and in various sperm activation mutants. While other members of the sperm activation pathway associate with the plasma membrane or localize to the sperm’s membranous organelles, SPE-6 surrounds the chromatin mass of unactivated sperm. During sperm activation by either of two semiautonomous signaling pathways, SPE-6 redistributes to the front, central region of the sperm’s pseudopod. When disrupted by reduction-of-function alleles, SPE-6 protein is either diminished in a temperature-sensitive manner (hc187) or is mis-localized in a stage-specific manner (hc163). During the multistep process of sperm activation, SPE-6 is released from its perinuclear location after the spike stage in a process that does not require fusion of membranous organelles with the plasma membrane. After activation, spermatozoa exhibit variable proportions of perinuclear and pseudopod-localized SPE-6, depending on their location within the female reproductive tract. These findings provide new insights regarding SPE-6’s role in sperm activation and suggest that extracellular signals during sperm migration may further modulate SPE-6 localization and function.

AbstractThe root Rhynchosia volubilis was widely used for contraception in folk medicine, although its molecular mechanism on antifertility has not yet been revealed. In human sperm, it was reported that the cation channel of sperm, an indispensable cation channel for the fertilization process, could be regulated by various steroid-like compounds in plants. Interestingly, these nonphysiological ligands would also disturb the activation of the cation channel of sperm induced by progesterone. Therefore, this study aimed to explore whether the compounds in R. volubilis affect the physiological regulation of the cation channel of sperm. The bioguided isolation of the whole herb of R. volubilis has resulted in the novel discovery of five new prenylated isoflavonoids, rhynchones A – E (1 – 5), a new natural product, 5′-O-methylphaseolinisoflavan (6) (1H and 13C NMR data, Supporting Information), together with twelve known compounds (7 – 18). Their structures were established by extensive spectroscopic analyses and drawing a comparison with literature data, while their absolute configurations were determined by electronic circular dichroism calculations. The experiments of intracellular Ca2+ signals and patch clamping recordings showed that rhynchone A (1) significantly reduced cation channel of sperm activation by competing with progesterone. In conclusion, our findings indicat that rhynchone A might act as a contraceptive compound by impairing the activation of the cation channel of sperm and thus prevent fertilization.

The aim of the present study was to investigate the spontaneous motility of spermatozoa and to optimize sperm collection, short-term sperm storage, and fertilization in zebrafish Danio rerio. The movement of spermatozoon in water was propagated along the flagellum at 16 s after sperm activation then damped from the end of the flagellum for 35 s and fully disappeared at 61 s after activation. For artificial fertilization, milt must be added to an immobilizing solution, which stops the movement of sperm and keeps the sperm motionless until fertilization. E400 and Kurokura as isotonic solutions were shown to be suitable extenders to store sperm for fertilization for 6 h. E400 stored sperm for 12 h at 0–2 °C. Sperm motility decreased only to 36% at 12 h post stripping for the E400 extender and to 19% for the Kurokura extender. To achieve an optimal level of fertilization and swim-up larvae rates, a test tube with a well-defined amount of 6,000,000 spermatozoa in E400 extender per 100 eggs and 100 µL of activation solution has proven to be more successful than using a Petri dish. The highest fertilization and swim-up larvae rates reached 80% and 40–60%, respectively, with milt stored for 1.5 h in the E400 extender at 0–2 °C.

Abstract Major sperm proteins (MSP) are a nematode-specific system of motor proteins required for amoeboid sperm movement. A number of MSP genes vary in different nematode species, but encoded protein sequences reveal high homology between these proteins. In fact, all studies of MSPs localization and functions are based exclusively on the representatives of the order Rhabditida belonging to the nematode class Chromadorea, while MSP-driven sperm movement in Enoplea, another major clade of the phylum Nematoda is still unconfirmed. In this study, we found out the presence of MSPs in the enoplean nematode Enoplus brevis (Enoplida) and compared MSP localization in sperm of this species with the chromadorean nematode Panagrellus redivivus (Rhabditida). Then, we analyzed the putative MSP sequences of both species. Our results indicate that MSPs are presented in E. brevis spermatozoa and form filamentous structures after sperm activation, which may be considered as the evidence of their motor functions similar to those in the spermatozoa of chromadorean nematodes. We found that E. brevis MSPs show lower homology to known proteins of rhabditids which species reveal hyper-conservatism in MSP protein sequences. It reflects evidently more distant evolutionary relationships of Enoplea and Chromadorea than exist within Rhabditida order. Our data denote necessity of reconsideration of view on MSP evolution within Nematoda.

The objectives of this study were to assess the cooling and freezing of donkey epididymal semen harvested immediately after castration (Experiment 1, n = 4) or after the shipment (24 or 48 h) of epididymides attached to testicles (Experiment 2, n = 14) or dissected apart (Experiment 3, n = 36). In each experiment, semen was frozen immediately (Non-Centrif) in an egg yolk-based semen extender (EY) or after processing through cushion-centrifugation (Centrif) while extended in a skim milk-based extender (SC). In all three experiments, cooled, pre-freeze, and post-thaw epididymal semen was assessed for total motility (TM), progressive motility (PM), plasma membrane integrity (PMI), and high mitochondrial membrane potential (HMMP). Data were analyzed with R using mixed models and Tukey’s test as posthoc. Results showed that the cooling of epididymal semen up to 24 h after harvesting did not affect motility parameters or plasma membrane integrity; furthermore, in Experiment 3, the post-thaw evaluation of both Centrif and Non-Centrif achieved similar TM and PM. Collectively, the post-thaw results revealed low motility parameters across groups; while, the PMI and HMMP did not reflect this trend, and the values remained high, suggesting that there was a lack of epididymal sperm activation with either centrifugation or extenders. In summary, freshly harvested and cooled-shipped and cooled semen had satisfactory semen parameters. Future studies need to address donkey epididymal semen fertility in mares and jennies.