Protein-Carbohydrate Interaction between Sperm and the Egg-Coating Envelope and Its Regulation by Dicalcin, a Xenopus laevis Zona Pellucida Protein-Associated Protein

The Olfactory Receptor Olfr25 Mediates Sperm Dysfunction Induced by Low-Dose Bisphenol A through the CatSper-Ca2+ Signaling Pathway

Bisphenol A (BPA), a typical endocrine disruptor, is known to have various adverse effects on the male reproductive system. However, the toxic effects and mechanisms of low-dose BPA have not yet been fully explored. In this study, male Kunming mice were orally administered low-dose BPA (0.03, 0.3 and 3 mg/kg/d) for ten consecutive weeks. Pathological sections of testicular tissue showed no significant morphological differences after BPA exposure. An analysis of the functional parameters of sperm revealed that exposure to low-dose BPA significantly decreased sperm motility, chemotaxis, and the acrosome reaction. An in vitro BPA exposure model combined with an omics data analysis showed that the olfactory receptor-related pathway was significantly enriched after BPA treatment. Subsequent experiments verified the reduced mRNA level of a novel olfactory receptor gene, Olfr25, in vivo and in vitro exposure models. Meanwhile, exposure to low-dose BPA reduced the intracellular calcium ion concentration and the mRNA levels of pore-forming subunits of the CatSper channel in sperm. Importantly, the knockdown of Olfr25 inhibited calcium ion levels and CatSper subunit expression in GC-2 cells. Olfr25 overexpression attenuated the BPA-induced downregulation of CatSper subunit expression in GC-2 cells. These findings indicate that Olfr25 might participate in low-dose BPA-induced sperm dysfunction by affecting the CatSper-Ca2+ signaling pathway. This study reveals a new mechanism underlying the effects of low-dose BPA on sperm function and provides a reference for assessing the safety of low-dose BPA exposure.

Targeted delivery of oligonucleotides using multivalent protein-carbohydrate interactions

Cell surface protein-carbohydrate interactions are essential for tissue-specific recognition and endocytosis of viruses, some bacteria and their toxins, and many glycoproteins. Often protein-carbohydrate interactions are multivalent - multiple copies of glycans bind simultaneously to multimeric receptors. Multivalency enhances both affinity and binding specificity, and is of interest for targeted delivery of drugs to specific cell types. The first such example of carbohydrate-mediated drug delivery to reach the clinic is Givosiran, a small interfering ribonucleic acid (siRNA) that is conjugated to a trivalent N-acetylgalactosamine (GalNAc) ligand. This ligand enables efficient uptake of the nucleic acid by the asialoglycoprotein receptor (ASGP-R) on hepatocytes. Synthetic multivalent ligands for ASGP-R were among the first 'cluster glycosides' developed at the birth of multivalent glycoscience around 40 years ago. In this review we trace the history of 'GalNAc targeting' from early academic studies to current pharmaceuticals and consider what other opportunities could follow the success of this delivery technology.

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

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

Diversity of sialic acids and sialoglycoproteins in gametes and at fertilization

Sialic acids are a family of 9-carbon monosaccharides with particular physicochemical properties. They modulate the biological functions of the molecules that carry them and are involved in several steps of the reproductive process. Sialoglycoproteins participate in the balance between species recognition and specificity, and the mechanisms of these aspects remain an issue in gametes formation and binding in metazoan reproduction. Sialoglycoproteins form a specific coat at the gametes surface and specific polysialylated chains are present on marine species oocytes. Spermatozoa are submitted to critical sialic acid changes in the female reproductive tract facilitating their migration, their survival through the modulation of the female innate immune response, and the final oocyte-binding event. To decipher the role of sialic acids in gametes and at fertilization, the dynamical changes of enzymes involved in their synthesis and removal have to be further considered.

The Association Between Follicular Fluid Sialic Acid Levels, Oocyte Quality, and Pregnancy Rates

Sialic acid residues perform important roles in both physiological and pathologic processes. Our aim was to measure the levels of sialic acid in the follicular fluid of women undergoing in vitro fertilization (IVF) and to assess correlations between IVF parameters and sialic acid levels. All women meeting the inclusion criteria underwent gonadotropin-releasing hormone agonist treatment and during oocyte retrieval, follicular fluids of mature follicles were collected and pooled for each patient. Correlation analysis was made between sialic acid levels and oocyte quality. Eighty-seven patients meeting the inclusion criteria were enrolled. In terms of oocyte quality and sialic acid, follicular fluid total sialic acid (FF-TSA) levels positively correlated with germinal vesicle oocytes and metaphase I oocytes. In terms of clinical parameters, no correlation between sialic acid levels and body mass index, serum levels of hormones, duration of infertility, and the total dose of gonadotropins was observed. The mean FF-TSA was 86.1±35.19 mg/dl in the clinical pregnancy positive group and was 73.64±22.15 mg/dl in the clinical pregnancy negative group. FF-TSA levels positively correlated with immature oocytes. This can be either as part of the normal oocyte maturation or as a compensatory mechanism against reactive oxygen species during the oocyte maturation process.

Capacitation in Plant and Animal Fertilization

Sexual reproduction relies on the successful fusion of the sperm and egg cell. Despite the vast differences between plants and animals, there are similarities at a molecular level between plant and animal reproduction. While the molecular basis of fertilization has been extensively studied in plants, the process of capacitation has received little attention until recently. Recent research has started to uncover the molecular basis of plant capacitation. Furthermore, recent studies suggest that the key molecules in plants and animal fertilization are functionally conserved. Here, we review new insights for our understanding of capacitation of pollen tube and fertilization in plants and also propose that there are commonalities in the process of sexual reproduction between plants and animals.

The Catsper channel and its roles in male fertility: a systematic review

The Catsper channel is a sperm-specific, Ca²⁺-permeable, pH-dependent, and low voltage-dependent channel that is essential for the hyperactivity of sperm flagellum, chemotaxis towards the egg, capacitation and acrosome reaction. All of these physiological events require calcium entry into sperm cells. Remarkably, Catsper genes are exclusively expressed in the testis during spermatogenesis, and are sensitive to ion channel-induced pH change, such as NHEs, Ca²⁺ATPase, K⁺ channel, Hv1 channel and HCO₃^- transporters. Furthermore, the Catsper channel is regulated by some physiological stimulants, such as progesterone, cyclic nucleotides (e.g., cAMP, cGMP), zona pellucida (ZP) glycoproteins and bovine serum albumin (BSA). All of these factors normally stimulate Ca²⁺ entry into sperm through the Catsper channel. In addition, the Catsper channel may be a potential target for male infertility treatment or contraception. This review will focus on the structure, functions, regulation mechanisms and medicinal targets of the Catsper channel.

Profiling N-glycans of the egg jelly coat of the sea urchin Paracentrotus lividus by MALDI-TOF mass spectrometry and capillary liquid chromatography electrospray ionization-ion trap tandem mass spectrometry systems

Sea urchin eggs are surrounded by a carbohydrate-rich layer, termed the jelly coat, that consists of polysaccharides and glycoproteins. In the present study, we describe two mass spectrometric strategies to characterize the N-glycosylation of the Paracentrotus lividus egg jelly coat, which has an alecithal-type extracellular matrix like mammalian eggs. Egg jelly was isolated, lyophilized, and dialyzed, followed by peptide N-glycosidase F (PNGase-F) treatment to release N-glycans from their protein chain. These N-glycans were then derivatized by permethylation reaction, and analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and capillary liquid chromatography electrospray ionization-ion trap tandem mass spectroscopy (CapLC ESI-Ion trap-MS/MS). N-glycans in the egg jelly coat glycoproteins were indicated by sodiated molecules at m/z 1579.8, 1783.9, 1988.0, 2192.0, and 2397.1 for permethylated oligosaccharides on MALDI-TOF MS. Fragmentation and structural characterization of these oligosaccharides were performed by ESI-Ion trap MS/MS. Then, MALDI-TOF-MS and ESI-Ion trap-MS/MS spectra were interpreted using the GlycoWorkbench software suite, a tool for building, displaying, and profiling glycan masses, to identify the original oligosaccharide structures. The oligosaccharides of the isolated egg jelly coat were mainly of the high mannose type.