Calcium channels in chicken sperm regulate motility and the acrosome reaction

Trace and essential elements as vital components to improve the performance of the male reproductive system: Implications in cell signaling pathways

Successful male fertilization requires the main processes such as normal spermatogenesis, sperm capacitation, hyperactivation, and acrosome reaction. The progress of these processes depends on some endogenous and exogenous factors. So, the optimal level of ions and essential and rare elements such as selenium, zinc, copper, iron, manganese, calcium, and so on in various types of cells of the reproductive system could affect conception and male fertility rates. The function of trace elements in the male reproductive system could be exerted through some cellular and molecular processes, such as the management of active oxygen species, involvement in the action of membrane channels, regulation of enzyme activity, regulation of gene expression and hormone levels, and modulation of signaling cascades. In this review, we aim to summarize the available evidence on the role of trace elements in improving male reproductive performance. Also, special attention is paid to the cellular aspects and the involved molecular signaling cascades.

Liquid semen storage-induced alteration in the protein composition of turkey (Meleagris gallopavo) spermatozoa

Liquid storage of turkey semen without the loss of fertilizing ability is of practical interest to the poultry industry. However, fertility rates from liquid-stored turkey semen decline within a few hours. A clear cause of the decline in spermatozoa quality remains unidentified. Therefore, the purpose of the present study was to monitor the dynamics of proteomic changes in spermatozoa during 48 h of liquid storage by 2-dimensional difference in-gel electrophoresis coupled with matrix-assisted laser desorption/ionization mass spectrometry. A total of 57 protein spots were differentially expressed between fresh and stored spermatozoa; 42 spots were more and 15 were less abundant after 48 h of semen storage. Raw proteomic data are available via ProteomeXchange with identifier PXD043050. The selected differentially expressed proteins (DEPs) were validated by western blotting and localized in specific spermatozoa structures by immunofluorescence, such as the head (acrosin and tubulin α), midpiece (acrosin, aconitate hydratase 2, and glycerol-3-phosphate dehydrogenase) and tail (tubulin α). Most of the DEPs that changed in response to liquid storage were related to flagellum-dependent cell motility, energy derivation through oxidation of organic compounds and induction of fertilization, suggesting the complexity of the processes leading to the decrease in stored semen quality. The damaging effect of liquid storage on spermatozoa flagellum manifested as more microtubule proteins, such as tubulins and tektins, most likely formed by posttranslational modifications, tubulin α relocation from the tail to the sperm head, which appeared after 48 h of semen storage, and decreases in fibrous shelf proteins at the same time. Motility could be affected by dysregulation of Ca2+-binding proteins and disturbances in energy metabolism in spermatozoa flagellum. Regarding sperm mitochondria, DEPs involved in energy derivation through the oxidation of organic compounds indicated disturbances in fatty acid beta oxidation and the tricarboxylic acid cycle as possible reasons for energy deficiency during liquid storage. Disturbances in acrosin and 1-phosphatidylinositol 4,5-bisphosphate phosphodiesterase zeta may be involved in rapid declines in the fertility potential of stored turkey spermatozoa. These results showed the complexity of the processes leading to a decrease in stored semen quality and broadened knowledge of the detrimental effects of liquid storage on turkey spermatozoa physiology.

Astaxanthin Improved the Quality of Hu Ram Semen by Increasing the Antioxidant Capacity and Mitochondrial Potential and Mitigating Free Radicals-Induced Oxidative Damage

The objective of this research was to investigate the effect of astaxanthin supplementations of semen extender on the quality of Hu ram semen after up to five days of preservation at 4 °C. Semen samples were collected from five healthy Hu rams using an artificial vagina during breeding season (April to August 2023) and diluted with a basic extender supplemented with control (0), 1 µM, 2 µM, 3.5 µM, or 4.5 µM of AXT. Overall, 170 semen ejaculate samples (34 repetitions) from five healthy Hu rams were used in our research study. The results revealed that the addition of AXT (3.5 µM) significantly (p ≤ 0.05) increased the sperm kinematic indexes (T.M%, P.M%, MAD%, STR%, and LIN %), sperm viability, plasma membrane integrity, acrosome integrity, total antioxidant content (T-AOC), and mitochondrial membrane potential (MMP) of the Hu rams spermatozoa after up to five days of preservation at 4 °C. Contrary to that, the addition of the best concentration of AXT (3.5 µM) to the semen extender significantly (p ≤ 0.05) reduced the reactive oxygen species (ROS) and malondialdehyde (MDA) concentration of Hu ram semen. In conclusion, the results of the current study indicate that the addition of a semen extender with AXT improves the quality of Hu ram spermatozoa by increasing the total antioxidant capacity (T-AOC) and mitochondrial membrane potential (MMP). On the other hand, reducing free radicals induced oxidative (ROS) and per oxidative (MDA) damage to Hu ram semen.

Signaling Roleplay between Ion Channels during Mammalian Sperm Capacitation

In order to accomplish their primary goal, mammalian spermatozoa must undergo a series of physiological, biochemical, and functional changes crucial for the acquisition of fertilization ability. Spermatozoa are highly polarized cells, which must swiftly respond to ionic changes on their passage through the female reproductive tract, and which are necessary for male gametes to acquire their functional competence. This review summarizes the current knowledge about specific ion channels and transporters located in the mammalian sperm plasma membrane, which are intricately involved in the initiation of changes within the ionic milieu of the sperm cell, leading to variations in the sperm membrane potential, membrane depolarization and hyperpolarization, changes in sperm motility and capacitation to further lead to the acrosome reaction and sperm-egg fusion. We also discuss the functionality of selected ion channels in male reproductive health and/or disease since these may become promising targets for clinical management of infertility in the future.

Astaxanthin Induces the Expression of CatSper1 Gene and Protects Sperms in Toxicity Induced by Cadmium in Mice

Cadmium (Cd) as a heavy metal damages testis and decreases fertility, however, antioxidants can improve sperm parameters and decrease male infertility. In this study we investigated the effect of astaxanthin (AST) on sperm parameters, expression levels of CatSper1 and CatSper2 genes in presence of Cd in mice. Thirty adults' mice were divided into 4 groups, sham group received olive oil and saline (olive oil is the solvent of AST and saline is the solvent of Cd), Cd group received 1 mg/kg Cdcl₂, a group received 10 mg/kg AST and 1 mg/kg Cdcl₂ and a group received 10 mg/kg AST. The treatments were done intraperitoneally for 14 days. After 14 days sperm parameters were analyzed. Malondialdehyde level, catalase enzyme activity, the alteration of CatSper1 and CatSper2 genes expression were measured in testis. Results showed that Sperm count, viability, CatSper1 gene expression and catalase activity significantly decreased by Cd compared to sham group. Cd significantly increased sperm DNA fragmentation (SDF), abnormal sperm morphology and malondialdehyd level compared to sham group. AST significantly increased sperm count, viability and CatSper1 gene expression and decreased SDF and abnormal sperm in comparison with Cd group. AST protected testis and decreased oxidative stress induced by Cd. Our findings indicated that AST could protect sperm DNA, enhanced CatSper1 gene expression and sperm quality in presence of Cd. No significant differences were found in CatSper2 expression among treatments. Therefore, AST as a strong antioxidant can help to protect the potential of fertility against Cd toxicity.

Research Note: The effect of crude protein and calcium intake on fertility of male broiler breeders

This experiment investigated the effect of excess crude protein and/or calcium on male broiler breeder fertility. Forty-eight broiler breeder males, from a group of 60 that consistently produced a semen sample were allocated to one of 4 dietary treatments, formulated to provide either the male or female recommendation for crude protein and calcium, or their combinations. Birds were provided a constant daily feed allocation. Semen samples were collected and assessed for concentration and sperm mobility index. Commercial laying hens were also inseminated and the points of sperm hydrolysis counted in the membranes of the eggs produced after insemination. Dietary crude protein had no significant effect on sperm concentration at any age, but significantly poorer sperm concentration was seen in the males fed high calcium at 42 and 57 wk of age, and a significant interaction was observed at 60 wk of age, with the poorest sperm concentration from birds fed high crude protein and high calcium. There was no significant effect at any age of crude protein or calcium on sperm mobility index. The birds fed levels of crude protein and calcium recommended for males had significantly more points of sperm hydrolysis at 40 wk of age compared to all other dietary treatments, which indicates better fertilizing potential. While there were a few incidences of birds fed a ration with levels of crude protein and calcium recommended for males showing superior sperm quality, this was not a consistent trend across all ages or measures of fertility. Therefore, males fed a female ration at the correct allocation to ensure adherence to the bodyweight curve should not exhibit reduced (or improved) fertility, however, there were instances where birds fed the male recommended concentration of CP and Ca had improved measures of sperm quality.

Structure and Function of Ion Channels Regulating Sperm Motility-An Overview

Sperm motility is linked to the activation of signaling pathways that trigger movement. These pathways are mainly dependent on Ca²⁺, which acts as a secondary messenger. The maintenance of adequate Ca²⁺ concentrations is possible thanks to proper concentrations of other ions, such as K⁺ and Na⁺, among others, that modulate plasma membrane potential and the intracellular pH. Like in every cell, ion homeostasis in spermatozoa is ensured by a vast spectrum of ion channels supported by the work of ion pumps and transporters. To achieve success in fertilization, sperm ion channels have to be sensitive to various external and internal factors. This sensitivity is provided by specific channel structures. In addition, novel sperm-specific channels or isoforms have been found with compositions that increase the chance of fertilization. Notably, the most significant sperm ion channel is the cation channel of sperm (CatSper), which is a sperm-specific Ca²⁺ channel required for the hyperactivation of sperm motility. The role of other ion channels in the spermatozoa, such as voltage-gated Ca²⁺ channels (VGCCs), Ca²⁺-activated Cl-channels (CaCCs), SLO K⁺ channels or voltage-gated H⁺ channels (VGHCs), is to ensure the activation and modulation of CatSper. As the activation of sperm motility differs among metazoa, different ion channels may participate; however, knowledge regarding these channels is still scarce. In the present review, the roles and structures of the most important known ion channels are described in regard to regulation of sperm motility in animals.

Characterization and biological role of cysteine-rich venom protein belonging to CRISPs from turkey seminal plasma†

Turkey semen contains cysteine-rich secretory proteins (CRISPs) that belong to the dominant seminal plasma proteins. We aimed to isolate and characterize CRISP from turkey seminal plasma and evaluate its possible involvement in yellow semen syndrome (YSS). YSS, which is well characterized, causes reduced fertility and hatchability. The protein was purified using hydrophobic interaction, gel filtration, and reverse phase chromatography. It then was subjected to identification by mass spectrometry, analysis of physicochemical properties, and specific antibody production. The biological function of the isolated protein was tested and included its effects on sperm motility and migration and sperm-egg interactions. Sperm motility was measured with the CASA system using Hobson Sperm Tracker. The reproductive tract of turkey toms was analyzed for gene expression; immunohistochemistry was used for protein localization in the male reproductive tract, spermatozoa, and inner perivitelline layer. The isolated protein was identified as cysteine-rich venom protein-like isoform X2 (CRVP X2; XP_010706464.1) and contained feature motifs of CRISP family proteins. Turkey CRVP X2 was present in both spermatozoa and seminal plasma. The extensive secretion of CRVP X2 by the epithelial cells of the epididymis and ductus deferens suggests its involvement in post-testicular sperm maturation. The internally localized CRVP X2 in the proximal part of the sperm tail might be responsible for stimulation of sperm motility. CRVP X2 on the sperm head might be involved in several events prior to fusion and may also participate in gamete fusion itself. Although the mechanisms by which CRVP X2 mediates fertilization are still unknown, the involvement of complementary sites cannot be excluded. The disturbance of CRVP X2 expression can serve as an etiologic factor of YSS in the turkey. This study expands the understanding of the detailed mechanism of fertilization in birds by clarifying the specific role of CRVP X2.

Sperm Cryopreservation in American Flamingo (Phoenicopterus Ruber): Influence of Cryoprotectants and Seminal Plasma Removal

The American flamingo is a useful model for the development of successful semen cryopreservation procedures to be applied to threatened related species from the family Phoenicopteridae, and to permit genetic material banking. Current study sought to develop effective sperm cryopreservation protocols through examining the influences of two permeating cryoprotectants and the seminal plasma removal. During two consecutive years (April), semen samples were collected and frozen from American flamingos. In the first year, the effect of two permeating cryoprotectants, DMA (dimethylacetamide) (6%) or Me2SO (dimethylsulphoxide) (8%), on frozen-thawed sperm variables were compared in 21 males. No differences were seen between DMA and Me2SO for sperm motility, sperm viability, and DNA fragmentation after thawing. In the second year, the role of seminal plasma on sperm cryoresistance was investigated in 31 flamingos. Sperm samples were cryopreserved with and without seminal plasma, using Me2SO (8%) as a cryoprotectant. The results showed that samples with seminal plasma had higher values than samples without seminal plasma for the following sperm variables: Straight line velocity (22.40 µm/s vs. 16.64 µm/s), wobble (75.83% vs. 69.40%), (p < 0.05), linearity (62.73% vs. 52.01%) and straightness (82.38% vs. 73.79%) (p < 0.01); but acrosome integrity was lower (55.56% vs. 66.88%) (p < 0.05). The cryoresistance ratio (CR) was greater in samples frozen with seminal plasma than without seminal plasma for CR-progressive motility (138.72 vs. 54.59), CR-curvilinear velocity (105.98 vs. 89.32), CR-straight line velocity (152.77 vs. 112.58), CR-average path velocity (122.48 vs. 98.12), CR-wobble (111.75 vs. 102.04) (p < 0.05), CR-linearity (139.41 vs. 113.18), and CR-straightness (124.02 vs. 109.97) (p < 0.01). This research demonstrated that there were not differences between Me2SO and DMA to successful freezing sperm of flamingos; seminal plasma removal did not provide a benefit for sperm cryopreservation.

Expression analysis of microRNAs and their target mRNAs of testes with high and low sperm motility in domestic pigeons (Columba livia)

Sperm motility is one of the most important indicators to evaluate poultry fertility. In order to explore key molecular regulation roles related to sperm motility, we employed testicular RNA sequencing of pigeon. A total of 705 known and 385 novel microRNAs were identified. Compared with the low sperm motility group, four upregulated and two downregulated miRNAs in the high sperm motility group were identified. A total of 3567 target mRNAs were predicted and four target mRNAs were selected to validate by qPCR. The miRNA-mRNA interaction network analysis, indicated that mmu-miR-183-5p /FOXO1 and PC-3p-244994_31/CHDH pairs might affect sperm motility. GO and KEGG annotation analysis showed that target genes of differentially expressed miRNAs were related to serine/threonine kinase activity, ATP binding, Wnt and MAPK signaling pathway. The study provided a global miRNAs transcriptome of pigeon and a novel insight into the expression of the miRNAs in testes that associated with sperm motility.

IP3R Channels in Male Reproduction

As a second messenger in cellular signal transduction, calcium signaling extensively participates in various physiological activities, including spermatogenesis and the regulation of sperm function. Abnormal calcium signaling is highly correlated with male infertility. Calcium signaling is mainly regulated by both extracellular calcium influx and the release of calcium stores. Inositol 1,4,5-trisphosphate receptor (IP3R) is a widely expressed channel for calcium stores. After being activated by inositol 1,4,5-trisphosphate (IP3) and calcium signaling at a lower concentration, IP3R can regulate the release of Ca²⁺ from stores into cytoplasm, and eventually trigger downstream events. The closure of the IP3R channel caused by a rise in intracellular calcium signals and the activation of the calcium pump jointly restores the calcium store to a normal level. In this review, we aim to discuss structural features of IP3R channels and the underlying mechanism of IP3R channel-mediated calcium signaling and further focus on the research progress of IP3R expression and function in the male reproductive system. Finally, we propose key directions and strategies for research of IP3R in spermatogenesis and the regulation of sperm function to provide more understanding of the function and mechanism of IP3R channel actions in male reproduction.

Src family kinases-mediated negative regulation of sperm acrosome reaction in chickens (Gallus gallus domesticus)

The acrosome reaction (AR) is a strictly-regulated, synchronous exocytosis that is required for sperm to penetrate ova. This all-or-nothing process occurs only once in the sperm lifecycle through a sequence of signaling pathways. Spontaneous, premature AR therefore compromises fertilization potential. Although protein kinase A (PKA) pathways play a central role in AR across species, the signaling network used for AR induction is poorly understood in birds. Mechanistic studies of mammalian sperm AR demonstrate that PKA activity is downstreamly regulated by Src family kinases (SFKs). Using SFK inhibitors, our study shows that in chicken sperm, SFKs play a role in the regulation of PKA activity and spontaneous AR without affecting motility. Furthermore, we examined the nature of SFK phosphorylation using PKA and protein tyrosine phosphatase inhibitors, which demonstrated that unlike in mammals, SFK phosphorylation in birds does not occur downstream of PKA and is primarily regulated by calcium-dependent tyrosine phosphatase activity. Functional characterization of SFKs in chicken sperm showed that SFK activation modulates the membrane potential and plays a role in inhibiting spontaneous AR. Employing biochemical isolation, we also found that membrane rafts are involved in the regulation of SFK phosphorylation. This study demonstrates a unique mechanism for regulating AR induction inherent to avian sperm that ensure fertilization potential despite prolonged storage.

Transcriptome analysis of turkey (Meleagris gallopavo) reproductive tract revealed key pathways regulating spermatogenesis and post-testicular sperm maturation

The application of transcriptomics to the study of the reproductive tract in male turkeys can significantly increase our current knowledge regarding the specifics of bird reproduction. To characterize the complex transcriptomic changes that occur in the testis, epididymis, and ductus deferens, deep sequencing of male turkey RNA samples (n = 6) was performed, using Illumina RNA-Seq. The obtained sequence reads were mapped to the turkey genome, and relative expression values were calculated to analyze differentially expressed genes (DEGs). Statistical analysis revealed 1,682; 2,150; and 340 DEGs in testis/epididymis, testis/ductus deferens, and epididymis/ductus deferens comparisons, respectively. The expression of selected genes was validated using quantitative real-time reverse transcriptase-polymerase chain reaction. Bioinformatics analysis revealed several potential candidate genes involved in spermatogenesis, spermiogenesis and flagellum formation in the testis, and in post-testicular sperm maturation in the epididymis and ductus deferens. In the testis, genes were linked with the mitotic proliferation of spermatogonia and the meiotic division of spermatocytes. Histone ubiquitination and protamine phosphorylation were shown to be regulatory mechanisms for nuclear condensation during spermiogenesis. The characterization of testicular transcripts allowed a better understanding of acrosome formation and development and flagellum formation, including axoneme structures and functions. Spermatozoa motility during post-testicular maturation was linked to the development of flagellar actin filaments and biochemical processes, including Ca2+ influx and protein phosphorylation/dephosphorylation. Spermatozoa quality appeared to be controlled by apoptosis and antioxidant systems in the epididymis and ductus deferens. Finally, genes associated with reproductive system development and morphogenesis were identified. To the best of our knowledge, this is the first genome-wide functional investigation of genes associated with tissue-specific processes in turkey reproductive tract. A catalog of genes worthy of further studies to understand the avian reproductive physiology and regulation was provided.

Ca2+ signaling in mammalian spermatozoa

Calcium is an essential ion which regulates sperm motility, capacitation and the acrosome reaction (AR), three processes necessary for successful fertilization. The AR enables the spermatozoon to penetrate into the egg. In order to undergo the AR, the spermatozoon must reside in the female reproductive tract for several hours, during which a series of biochemical transformations takes place, collectively called capacitation. An early event in capacitation is relatively small elevation of intracellular Ca²⁺ (in the nM range) and bicarbonate, which collectively activate the soluble adenylyl cyclase to produce cyclic-AMP; c-AMP activates protein kinase A (PKA), leading to indirect tyrosine phosphorylation of proteins. During capacitation, there is an increase in the membrane-bound phospholipase C (PLC) which is activated prior to the AR by relatively high increase in intracellular Ca²⁺ (in the μM range). PLC catalyzes the hydrolysis of phosphatidyl-inositol-4,5-bisphosphate (PIP₂) to diacylglycerol and inositol-trisphosphate (IP₃), leading to activation of protein kinase C (PKC) and the IP₃-receptor. PKC activates a Ca²⁺- channel in the plasma membrane, and IP₃ activates the Ca²⁺- channel in the outer acrosomal membrane, leading to Ca²⁺ depletion from the acrosome. As a result, the plasma-membrane store-operated Ca²⁺ channel (SOCC) is activated to increase cytosolic Ca²⁺ concentration, enabling completion of the acrosome reaction. The hydrolysis of PIP₂ by PLC results in the release and activation of PIP₂-bound gelsolin, leading to F-actin dispersion, an essential step prior to the AR. Ca²⁺ is also involved in the regulation of sperm motility. During capacitation, the sperm develops a unique motility pattern called hyper-activated motility (HAM) which is essential for successful fertilization. The main Ca²⁺-channel that mediates HAM is the sperm-specific CatSper located in the sperm tail.

AMPK Function in Mammalian Spermatozoa

AMP-activated protein kinase AMPK regulates cellular energy by controlling metabolism through the inhibition of anabolic pathways and the simultaneous stimulation of catabolic pathways. Given its central regulator role in cell metabolism, AMPK activity and its regulation have been the focus of relevant investigations, although only a few studies have focused on the AMPK function in the control of spermatozoa's ability to fertilize. This review summarizes the known cellular roles of AMPK that have been identified in mammalian spermatozoa. The involvement of AMPK activity is described in terms of the main physiological functions of mature spermatozoa, particularly in the regulation of suitable sperm motility adapted to the fluctuating extracellular medium, maintenance of the integrity of sperm membranes, and the mitochondrial membrane potential. In addition, the intracellular signaling pathways leading to AMPK activation in mammalian spermatozoa are reviewed. We also discuss the role of AMPK in assisted reproduction techniques, particularly during semen cryopreservation and preservation (at 17 °C). Finally, we reinforce the idea of AMPK as a key signaling kinase in spermatozoa that acts as an essential linker/bridge between metabolism energy and sperm's ability to fertilize.

Comparative transcriptomic analysis of high and low egg-producing duck ovaries

The egg-laying rate is an important indicator of egg production of laying ducks. Egg production directly impacts the economic benefits of the duck industry. In order to obtain better insight into the molecular mechanisms associated with the process of egg production, comparative transcriptomic analysis of the ovaries of Jinding ducks with high and low egg production was performed using the Illumina HiSeq 2500 system. A total of 843 differentially expressed genes (DEGs) was identified, 367 that were down-regulated and 476 that were up-regulated in high egg production (HEP) ovaries, as compared with low egg production (LEP) ovaries. Some genes, such as MC5R, APOD, ORAI1, and DYRK4, were more active in HEP ovaries, indicating that these genes may play important roles in regulation of egg production. Among these 843 DEGs, 685 were assigned to gene ontology (GO) categories. Of these, 25 genes were related to reproduction, and 30 were related to the reproductive process, including some associated with ovarian follicle development, circadian regulation of gene expression, circadian rhythm, and estrogen receptor binding. Furthermore, some important functional pathways were revealed, such as the steroid biosynthesis pathway, the endocrine and other factor-regulated calcium reabsorption pathways, circadian rhythm, the neuroactive ligand-receptor interaction pathway, fatty acid biosynthesis, and the calcium-signaling pathway, which appear to be much more active in the HEP group, as compared to those of the LEP group. The results of this study provide very useful information that may contribute to future functional studies of genes involved in bird reproduction.

Genomic identification, expression profiling, and functional characterization of CatSper channels in the bovine

Cation channels of sperm (CatSper) are sperm-specific calcium channels with identified roles in the regulation of sperm function in humans, mice, and horses. We sought to employ a comparative genomics approach to identify conserved CATSPER genes in the bovine genome, and profile their expression in reproductive tissue. We hypothesized that CATSPER proteins expressed in bull testicular tissue mediates sperm hyperactivation and their rheotactic response in the reproductive tract of the cow. Bioinformatic analysis identified all four known CATSPER genes (CATSPER 1-4) in the bovine genome, and profiling by quantitative real-time polymerase chain reaction identified site-specific variation in messenger ribonucleic acid (mRNA) expression for all four genes along the reproductive tract of the bull. Using a novel antibody against CATSPER 1, protein expression was confirmed and localized to the principal piece of bull sperm, in agreement with what has been reported in other species. Subsequent treatment of bull sperm with either the calcium chelator ethylene glycol tetraacetic acid; mibefradil, a specific blocker of CatSper channels in human sperm; or CATSPER1 antibody all significantly inhibited caffeine-induced hyperactivation and the rheotactic response, supporting the concept that the calcium influx occurs via CatSper channels. Taken together, the work here provides novel insights into expression and function of CatSper channels in bull testicular tissue and in the function of ejaculated sperm.

IFT25, an intraflagellar transporter protein dispensable for ciliogenesis in somatic cells, is essential for sperm flagella formation

Intraflagellar transport (IFT) is a conserved mechanism essential for the assembly and maintenance of most eukaryotic cilia and flagella. However, IFT25, a component of the IFT complex, is not required for the formation of cilia in somatic tissues. In mice, the gene is highly expressed in the testis, and its expression is upregulated during the final phase when sperm flagella are formed. To investigate the role of IFT25 in sperm flagella formation, the gene was specifically disrupted in male germ cells. All homozygous knockout mice survived to adulthood and did not show any gross abnormalities. However, all homozygous knockout males were completely infertile. Sperm numbers were reduced and these sperm were completely immotile. Multiple morphological abnormalities were observed in sperm, including round heads, short and bent tails, with some tails showing branched flagella and others with frequent abnormal thicknesses, as well as swollen tips of the tail. Transmission electron microscopy revealed that flagellar accessory structures, including the fibrous sheath and outer dense fibers, were disorganized, and most sperm had also lost the "9+2" microtubule structure. In the testis, IFT25 forms a complex with other IFT proteins. In Ift25 knockout testes, IFT27, an IFT25 binding partner, was missing, and IFT20 and IFT81 levels were also reduced. Our findings suggest that IFT25, although not necessary for the formation of cilia in somatic cells, is indispensable for sperm flagellum formation and male fertility in mice.

Acrosomal alkalization triggers Ca2+ release and acrosome reaction in mammalian spermatozoa

The sperm acrosome reaction (AR), an essential event for mammalian fertilization, involves Ca²⁺ permeability changes leading to exocytosis of the acrosomal vesicle. The acrosome, an intracellular Ca²⁺ store whose luminal pH is acidic, contains hydrolytic enzymes. It is known that acrosomal pH (pH_acr ) increases during capacitation and this correlates with spontaneous AR. Some AR inducers increase intracellular Ca²⁺ concentration ([Ca²⁺ ]_i ) through Ca²⁺ release from internal stores, mainly the acrosome. Catsper, a sperm specific Ca²⁺ channel, has been suggested to participate in the AR. Curiously, Mibefradil and NNC55-0396, two CatSper blockers, themselves elevate [Ca²⁺ ]_i by unknown mechanisms. Here we show that these compounds, as other weak bases, can elevate pH_acr , trigger Ca²⁺ release from the acrosome, and induce the AR in both mouse and human sperm. To our surprise, μM concentrations of NNC55-0396 induced AR even in nominally Ca²⁺ free media. Our findings suggest that alkalization of the acrosome is critical step for Ca²⁺ release from the acrosome that leads to the acrosome reaction.

Characterization of the functions and proteomes associated with membrane rafts in chicken sperm

Cellular membranes are heterogeneous, and this has a great impact on cellular function. Despite the central role of membrane functions in multiple cellular processes in sperm, their molecular mechanisms are poorly understood. Membrane rafts are specific membrane domains enriched in cholesterol, ganglioside GM1, and functional proteins, and they are involved in the regulation of a variety of cellular functions. Studies of the functional characterization of membrane rafts in mammalian sperm have demonstrated roles in sperm-egg binding and the acrosomal reaction. Recently, our biochemical and cell biological studies showed that membrane rafts are present and might play functional roles in chicken sperm. In this study, we isolated membrane rafts from chicken sperm as a detergent-resistant membranes (DRM) floating on a density gradient in the presence of 1% Triton X-100, and characterized the function and proteomes associated with these domains. Biochemical comparison of the DRM between fresh and cryopreserved sperm demonstrated that cryopreservation induces cholesterol loss specifically from membrane rafts, indicating the functional connection with reduced post-thaw fertility in chicken sperm. Furthermore, using an avidin-biotin system, we found that sperm DRM is highly enriched in a 60 KDa single protein able to bind to the inner perivitelline layer. To identify possible roles of membrane rafts, quantitative proteomics, combined with a stable isotope dimethyl labeling approach, identified 82 proteins exclusively or relatively more associated with membrane rafts. Our results demonstrate the functional distinctions between membrane domains and provide compelling evidence that membrane rafts are involved in various cellular pathways inherent to chicken sperm.

The Seminal fluid proteome of the polyandrous Red junglefowl offers insights into the molecular basis of fertility, reproductive ageing and domestication

Seminal fluid proteins (SFPs) are emerging as fundamental contributors to sexual selection given their role in post-mating reproductive events, particularly in polyandrous species where the ejaculates of different males compete for fertilisation. SFP identification however remains taxonomically limited and little is known about avian SFPs, despite extensive work on sexual selection in birds. We characterize the SF proteome of the polyandrous Red junglefowl, Gallus gallus, the wild species that gave rise to the domestic chicken. We identify 1,141 SFPs, including proteins involved in immunity and antimicrobial defences, sperm maturation, and fertilisation, revealing a functionally complex SF proteome. This includes a predominant contribution of blood plasma proteins that is conserved with human SF. By comparing the proteome of young and old males with fast or slow sperm velocity in a balanced design, we identify proteins associated with ageing and sperm velocity, and show that old males that retain high sperm velocity have distinct proteome characteristics. SFP comparisons with domestic chickens revealed both qualitative and quantitative differences likely associated with domestication and artificial selection. Collectively, these results shed light onto the functional complexity of avian SF, and provide a platform for molecular studies of fertility, reproductive ageing, and domestication.