Chemical and physical requirements for lipid extraction by bovine binder of sperm BSP1

Metabolites assay offers potential solution to improve the rooster semen cryopreservation

Semen cryopreservation represents a promising technology utilized for preserving high-quality chicken varieties in husbandry practices. However, the efficacy of this methodology is significantly impeded by the diminished quality of sperm. Metabolites, as the end products of metabolic reactions, serve as indicators of biological processes and offer insights into physiological conditions. In this study, we investigaged the sperm quality and alteration in metabolic profiles during the cryopreservation of Longyou Partridge Chicken semen. Following artificial semen collection, four groups of semen samples were established based on four points of the cryopreservation process (Ⅰ, fresh semen; Ⅱ, semen added extender and chilled at 4 °C for 30 min; Ⅲ, semen added cryoprotectants; Ⅳ, semen gradient freezed and stored in liquid nitrogen). Semen cryopreservation has a negative effect on the percentage of sperm in a straight-line trajectory (LIN), has no significant effect on total motile sperms (TM) or the proportion of sperm with typical morphology (NM). Metabolites were identified using LC-MS technique and analyses including Principal Component Analysis (PCA), Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA), Univariate statistical analysis, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) database were employed to identify metabolites. A total of 2471 metabolites had been identified, with the majority of the list being made up of amino acids and their metabolites as well as benzene and substituted derivatives. Group II exhibits 882 metabolites with significantly elevated abundance relative to Group I, alongside 37 metabolites displaying decreased abundance. In Group III, 836 metabolites demonstrate notably augmented abundance compared to Group II, while 87 metabolites exhibit reduced abundance. Furthermore, Group IV showcases 513 metabolites with markedly heightened abundance in comparison to Group III, and 396 metabolites with decreased abundance. Specific metabolites such as 5-Hydroxylysine, Phosphocholine, and alpha-d-glucose-6-phosphate exhibited a progressive decline during the cryopreservation process, correlating with either dilution and chilling, cryoprotectant addition, or freezing. In conclusion, our investigation systematically examined the changes of seminal metabolome and sperm quality throughout the cryopreservation process of rooster semen.

Genetic Diversity and Signatures of Selection for Thermal Stress in Cattle and Other Two Bos Species Adapted to Divergent Climatic Conditions

Understanding the biological mechanisms of climatic adaptation is of paramount importance for the optimization of breeding programs and conservation of genetic resources. The aim of this study was to investigate genetic diversity and unravel genomic regions potentially under selection for heat and/or cold tolerance in thirty-two worldwide cattle breeds, with a focus on Chinese local cattle breeds adapted to divergent climatic conditions, Datong yak (Bos grunniens; YAK), and Bali (Bos javanicus) based on dense SNP data. In general, moderate genetic diversity levels were observed in most cattle populations. The proportion of polymorphic SNP ranged from 0.197 (YAK) to 0.992 (Mongolian cattle). Observed and expected heterozygosity ranged from 0.023 (YAK) to 0.366 (Sanhe cattle; SH), and from 0.021 (YAK) to 0.358 (SH), respectively. The overall average inbreeding (±SD) was: 0.118 ± 0.028, 0.228 ± 0.059, 0.194 ± 0.041, and 0.021 ± 0.004 based on the observed versus expected number of homozygous genotypes, excess of homozygosity, correlation between uniting gametes, and runs of homozygosity (ROH), respectively. Signatures of selection based on multiple scenarios and methods (F ST, HapFLK, and ROH) revealed important genomic regions and candidate genes. The candidate genes identified are related to various biological processes and pathways such as heat-shock proteins, oxygen transport, anatomical traits, mitochondrial DNA maintenance, metabolic activity, feed intake, carcass conformation, fertility, and reproduction. This highlights the large number of biological processes involved in thermal tolerance and thus, the polygenic nature of climatic resilience. A comprehensive description of genetic diversity measures in Chinese cattle and YAK was carried out and compared to 24 worldwide cattle breeds to avoid potential biases. Numerous genomic regions under positive selection were detected using three signature of selection methods and candidate genes potentially under positive selection were identified. Enriched function analyses pinpointed important biological pathways, molecular function and cellular components, which contribute to a better understanding of the biological mechanisms underlying thermal tolerance in cattle. Based on the large number of genomic regions identified, thermal tolerance has a complex polygenic inheritance nature, which was expected considering the various mechanisms involved in thermal stress response.

Lipid selectivity in detergent extraction from bilayers

Despite numerous studies on detergent-induced solubilization of membranes and on the underlying mechanisms associated with this process, very little is known regarding the selectivity of detergents for lipids during their extraction from membranes. To get insights about this phenomenon, solubilization of model bilayers prepared from binary lipid mixtures by different detergents was examined. Three commonly used detergents were used: the non-ionic Triton X-100 (TX), the negatively-charged sodium dodecylsulfate (SDS), and the positively-charged n-dodecyltrimethylammonium chloride (DTAC). Two model membranes were used in order to identify if specific intermolecular interactions can lead to lipid selectivity: bilayers made of a binary mixture of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), and of a binary mixture of POPC and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG). Therefore, it was possible to describe systems presenting a combination of detergents bearing different charges with bilayers with different polymorphic propensities and charge. In conditions for which partial solubilization was observed, the composition of the extracted lipid phase was quantified with Liquid Chromatography coupled to Mass Spectrometry to elucidate whether a lipid selectivity occurred in the solubilization process. On one hand, it is found that repulsive or attractive electrostatic interactions did not lead to any lipid selectivity. On the other hand, POPE was systematically less extracted than POPC, regardless of the detergent nature. We propose that this lipid selectivity is inherent to the molecular shape of POPE unsuited for micelles curvature properties.

Assessment of binder of sperm protein 1 (BSP1) and heparin effects on in vitro capacitation and fertilization of bovine ejaculated and epididymal sperm

The present study evaluated the effect of binder of sperm protein 1 (BSP1) and/or heparin on in vitro bovine capacitation and fertilization rates using epididymal and ejaculated bovine sperm. Frozen-thawed sperm were selected and used in the following treatments. Control group: Fert-TALP medium without heparin; heparin (HEP) group: Fert-TALP with heparin (10 UI/ml); BSP1 group: Fert-TALP medium with BSP1 (10 µg/ml for ejaculated sperm; 40 µg/ml for epididymal sperm); HEP + BSP1 group: Fert-TALP medium with heparin (5 UI/ml) and BSP1 (5 µg/ml for ejaculated sperm; 20 µg/ml for epididymal sperm) and determined in vitro capacitation rates in different interval times (0, 15, 30 and 60 min) using the chlortetracycline fluorescence (CTC) method. Also, we evaluated the development rates of oocytes fertilized with ejaculated or epididymal sperm into the same treatments. Capacitation was greater and faster when ejaculated sperm were treated for 60 min with heparin compared with other treatments. However, developmental rates were similar in all treatments. For epididymal sperm, the treatments with BSP1 presented higher capacitation and fertilization rates compared with heparin (P < 0.05). The effects of heparin + BSP1 on capacitation and developmental rates did not cause any increase in capacitation or blastocyst rates compared with other groups for ejaculated or epididymal sperm. In conclusion, this study confirmed that either BSP1 and heparin can be used as capacitator agents for bovine ejaculated sperm during IVF. However, BSP1 seems to be more efficient compared with heparin for epididymal sperm. Furthermore, BSP1 and heparin have no synergic effects on sperm capacitation.

Comparison Between an Animal-Derived Product Medium and a Chemically Defined Medium for Ram Sperm Cryopreservation

Animal-derived products are widely used in sperm cryopreservation for their cryoprotective properties. These components, however, tend to be replaced because of sanitary risks. STEMALPHA.CRYO3 (Ref. 5617; Stem Alpha, Saint-Genis-l'Argentière, France), called "CRYO3," is a chemically defined preservation medium currently used for freezing human tissue and adult stem cells. The aim of this study was to evaluate the effect of a CRYO3-based medium on ram sperm freezing regarding in vitro parameters and in vivo fertility. Semen from nine Charolais rams was collected using an artificial vagina, then split and frozen using two media: a CRYO3-based medium or a control medium containing egg yolk (10%) and milk (45%). Sperm membrane integrity (propidium iodide [PI]/SYBR-14 and calcein AM/ethidium homodimer-1), acrosome integrity (FITC-PNA/PI), and mitochondrial membrane potential (JC-1) were assessed using flow cytometry, while functional membrane integrity was assessed using a hypo-osmotic swelling test and motility parameters, evaluated by computer-assisted sperm analysis. Pregnancy rates, prolificacy, and the average daily weight gain (DWG) of lambs were evaluated after performing 195 laparoscopic inseminations. The control medium showed significantly higher results than CRYO-based medium for all in vitro parameters, except for linearity and straightness (motions parameters). Conversely, field trials showed no significant difference between the control medium and the CRYO3-based medium for pregnancy rates (72.2% and 67.9%, respectively), prolificacy (1.8 and 1.6, respectively), and the DWG (0.34 and 0.35 kg/d, respectively). This preliminary study showed that CRYO3 cannot replace egg yolk and milk in freezing extenders for commercial purposes. However, as laparoscopic inseminations allowed a 67% pregnancy rate, CRYO3-based medium remains an option for international transport or long-term storage of genetic diversity.

Melittin-Induced Lipid Extraction Modulated by the Methylation Level of Phosphatidylcholine Headgroups

Protein- and peptide-induced lipid extraction from membranes is a critical process for many biological events, including reverse cholesterol transport and sperm capacitation. In this work, we examine whether such processes could display specificity for some lipid species. Melittin, the main component of dry bee venom, was used as a model amphipathic α-helical peptide. We specifically determined the modulation of melittin-induced lipid extraction from membranes by the change of the methylation level of phospholipid headgroups. Phosphatidylcholine (PC) bilayers were demethylated either by substitution with phosphatidylethanolamine (PE) or chemically by using mono- and dimethylated PE. It is shown that demethylation reduces the association of melittin with membranes, likely because of the resulting tighter chain packing of the phospholipids, which reduces the capacity of the membranes to accommodate inserted melittin. This reduced binding of the peptide is accompanied by an inhibition of the lipid extraction caused by melittin. We demonstrate that melittin selectively extracts PC from PC/PE membranes. This selectivity is proposed to be a consequence of a PE depletion in the surroundings of bound melittin to minimize disruption of the interphospholipid interactions. The resulting PC-enriched vicinity of melittin would be responsible for the observed formation of PC-enriched lipid/peptide particles resulting from the lipid efflux. These findings reveal that modulating the methylation level of phospholipid headgroups is a simple way to control the specificity of lipid extraction from membranes by peptides/proteins and thereby modulate the lipid composition of the membranes.

Addition of L-arginine to the fertilization medium enhances subsequent bovine embryo development rates

Although L-Arginine (ARG) has been reported as a promising bovine sperm capacitation agent, its effects on embryo development are still poorly understood. Herein, we compared the effects of ARG and/or heparin (HEP) addition to the fertilization medium for bovine oocytes on sperm capacitation and embryo development. We chose 10 mM ARG based on blastocyst development rates in a titration experiment. Addition of ARG and/or HEP to the fertilization medium resulted in similar rates of blastocyst development (P > 0.05). However, when ARG, but not HEP, was combined with a nitric oxide (NO) synthase inhibitor (N-Nitro-L-ARG-methyl ester, 10 mM) blastocyst development was decreased (P < 0.05). To assess the effects on capacitation, bovine sperm were incubated for 0, 3, and 6 hours in fertilization medium containing ARG and/or HEP and/or N-Nitro-L-ARG-methyl esterand acrosomal exocytosis rates were evaluated using fluorescein isothiocyanate conjugated Pisum sativum lectin (FITC-PSA) staining and flow cytometry. With HEP, acrosomal exocytosis rates were highest by 3 hours of incubation; however, by 6 hours, rates were similar for HEP and/or ARG (P > 0.05) and higher than those in control media (P < 0.05). Although both ARG and HEP increased sperm NO production (P < 0.05), combination with L-NAME only precluded acrosomal exocytosis when ARG added alone in the medium (P > 0.05). These results suggest that although both ARG and HEP supported sperm capacitation, only the effects of the former were driven via NO production. Moreover, ARG was also as effective as HEP at improving blastocyst development rates. Therefore, ARG may be used as a low-cost alternative sperm capacitation agent for bovine in vitro embryo production.

Purification of binder of sperm protein 1 (BSP1) and its effects on bovine in vitro embryo development after fertilization with ejaculated and epididymal sperm

The present study evaluated functional aspects of binder of sperm 1 (BSP1) in the bovine species. In a first experiment, cumulus-oocyte complexes (n = 1274) were incubated with frozen-thawed ejaculated sperm (18 hours) in Fert-TALP medium containing: heparin, 10, 20, or 40 μg/mL BSP1. Heparin followed by gelatin affinity chromatography was used for purification of BSP1 from bovine seminal vesicle fluid. With ejaculated sperm, cleavage rates were similar when Fert-TALP medium was incubated with heparin (74.1 ± 2.7%), 10 μg/mL BSP1 (77.8 ± 3.1%), or 20 μg/mL BSP1 (74 ± 2.0%). Day-7 blastocyst rates were equivalent after incubations with heparin (40.8 ± 5.0%) and 10 μg/mL BSP1 (34.1 ± 4.4%), but reduced after 20 μg/mL BSP1 (22.4 ± 2.9%) and 40 μg/mL BSP1 (19.3 ± 4.1%; P < 0.05). In the second experiment, cumulus-oocyte complexes (n = 1213) were incubated with frozen-thawed cauda epididymal sperm (18 hours) in Fert-TALP medium containing: no heparin, heparin, 10, 20, or 40 μg/mL. Cleavage and blastocyst rates were similar after treatments with heparin (68.5 ± 1.3% and 24.7 ± 3.2%, respectively) or without heparin (65.5 ± 1.8% and 27.3 ± 1.6%, respectively). Cleavage was higher after treatment with any BSP1 concentrations (74.2 ± 2.7%-79.0 ± 1.1%) than without heparin (P < 0.05). Also, cleavage was better after Fert-TALP medium incubation with 40 μg/mL BSP1 (79.0 ± 1.1%) than with heparin (68.5 ± 1.3%; P < 0.05). Embryo development was higher (P < 0.05) after treatment with 20 μg/mL BSP1 (35.6 ± 2.5%) and 40 μg/mL (41.1 ± 2%) than after incubations with heparin (24.7 ± 3.2%) or without heparin (27.3 ± 1.6%). Interestingly, BSP1 did not cause reductions in blastocyst rates after fertilization with epididymal sperm, as observed with ejaculated sperm. On the basis of immunocytochemistry, there was BSP1 binding to frozen-thawed ejaculated but not to epididymal sperm. Also, anti-BSP1 reaction remained on ejaculated sperm (as expected) and appeared on epididymal sperm after incubation with purified BSP1. Acrosome reaction of ejaculated and epididymal sperm was induced after incubation with purified BSP1 as well, indicating an effect of BSP1 on capacitation. In conclusion, purified BSP1 from bull seminal vesicles was able to bind to and induce capacitation of ejaculated and epididymal sperm. Also, BSP1 added to fertilization media and allowed proper cleavage and embryo development, with the effects being modulated by previous exposure or not of spermatozoa to seminal plasma.

Functional characterization of the domains of the bovine binder of SPerm 5 (BSP5) protein

BACKGROUND

Bovine BSP5 is a multifunctional protein primarily involved in sperm capacitation. BSP5 consists of long N-terminal part followed by two similar and highly conserved fibronectin type II domains designated A and B.

METHODS

In order to assess the role of these domains in the sperm binding and capacitation processes, we created recombinant individual domains (N, A, B), series of overlapping domains (NA and AB) and full-length BSP5 in an Escherichia coli expression system. The recombinant constructs were also tested for their ability to interact with ligands such as gelatine, heparin, chondroitin sulphate B and phosphatidylcholine liposomes by affinity chromatography and co-sedimentation studies.

RESULTS

With the exception of the N domain, all recombinant constructs retained gelatine, phosphatidylcholine, heparin and chondroitin sulphate B binding activities. Domain-wise studies showed clearly that AB domain is capable of performing its biological functions as well as the full-length protein, as it was able to potentiate heparin-mediated sperm capacitation.

CONCLUSIONS

These results indicate that the C-terminal domain composed of two Fn2 domains is sufficient and crucial to maintain the biological functions of BSP proteins. The N-terminal part of the protein did not bind to any of known BSP5-ligands including epididymal sperm and did not seem to be required for either sperm binding or sperm capacitation. This study also confirmed that glycosylation is not required for BSP-mediated sperm capacitation or any of the binding characteristics displayed by BSP5.