Identification and validation of ram sperm proteins associated with cryoinjuries caused by the cryopreservation process

Optimization of canine sperm cryopreservation by focusing on glycerol concentration and freezing rate

The purpose of this study was to improve the quality of frozen-thawed canine spermatozoa through the optimization of glycerol concentration (GC) and freezing rate in the semen freezing protocol. Ejaculates from nine dogs were diluted with an extender containing 0%, 1.5%, 3%, 6%, or 9% glycerol. The suspensions were loaded into 0.25 ml straws, frozen in nitrogen vapor in a closed box, and immersed in liquid nitrogen (LN2). The freezing rate was controlled by setting the distance from the LN2 surface to the straws as 1, 4, 7, or 10 cm. Firstly, freezing curves for each GC and freezing rate were analyzed. The analysis showed that the temperature of ice nucleation, freezing point, and immersion were changed with a certain trend depending on the GCs and freezing rates. Secondly, the sperm motility index (MI), viability and mitochondrial (MT) activity were evaluated. At 0 h after thawing, the MI was higher in the 3% and 6% GCs than the 0% GCs (P < 0.05). At 24 h, the 3% GC with 1 cm LN2 distance (1 cm-3%) and the 7 cm-6% showed higher viability than the other conditions (P < 0.05), and the highest MT activity was obtained in the 1 cm-3%, which was higher than the other conditions (P < 0.05). The present findings indicate that the rapid freezing rate at 1 cm (average - 31 °C/min) with 3% GC provided the optimal condition in this study; use of this condition should reduce the detrimental damage to dog spermatozoa caused by ice crystal formation during freezing.

Proteostasis as a Sentry for Sperm Quality and Male Fertility

In the last two decades, a school of thought emerged that perceives male reproductive health, testicular function, and sperm output as a sentry for general, somatic health. Large-scale epidemiologic studies have already linked the reduced sperm count to increased risk of chronic somatic disease (e.g., cancer, cardiovascular, neurological and bone diseases), yet most of these studies have not taken full advantage of advanced andrological analysis. Altered proteostasis, i.e., the disbalance between protein synthesis and turnover, is a common denominator of many diseases, including but not limited to cancer and neurodegenerative diseases. This chapter introduces the concept of cellular proteostasis as a measure of sperm structural and functional integrity and an endpoint of varied impacts on spermiogenesis and sperm maturation, including heritability, general health, lifestyle, and occupational and environmental reprotoxic exposure. Special consideration is given to small molecule protein modifiers, sperm-binding seminal plasma proteins, zinc-interacting proteins, and redox proteins responsible for the maintenance of protein structure and the protection of spermatozoa from oxidative damage. While the main focus is on human male infertility, serious consideration is given to relevant animal models, and in particular to male food animals with extensive records of fertility from artificial insemination services. Altogether, the proteostatic biomarker discovery and validation studies set the stage for the integration of proteomics of sperm proteostasis with genomic and high throughput phenomic approaches to benefit both human and animal reproductive medicine.

Integrating proteomics and metabolomics to evaluate impact of semen collection techniques on the quality and cryotolerance of goat semen

Results of artificial insemination (AI) are affected by changes in sperm quality and the function throughout collection and preservation procedures. Proteome and metabolome alterations of sperm treated with the different procedures in goat, however, aren't fully understood. To this end, we sought to investigate the impacts of rectal probe electrostimulation (EE) and artificial vagina (AV) semen collection methods on the quality and the cryotolerance of goat sperm, with additional focus on proteomic and metabolomic analyses. Semen samples were collected from Yunshang black goats and categorized into four groups: fresh sperm collected via AV (XAZ), fresh sperm collected via EE (XEZ), frozen sperm post-AV collection (DAZ) and frozen sperm post-EE collection (DEZ). Four comparisons (XAZ vs. XEZ, DAZ vs. XAZ, DEZ vs. XEZ, DAZ vs. DEZ) were performed, respectively. This study first evaluated sperm motility, acrosome integrity, plasma membrane integrity, mitochondrial activity, and reactive oxygen species (ROS) levels. The results indicated that there were no significant differences in fresh sperm quality parameters between the EE and AV methods. However, notable differences emerged post-cryopreservation. Specifically, the AV method proved more advantageous in preserving the motility, integrities of acrosome and plasma membrane, mitochondrial activity of frozen sperm compared to the EE method. Through the multi-omics approaches, a total of 210 differentially abundant proteins (DAPs) related to sperm characteristics and function were identified across the four comparations. Moreover, 32 differentially abundant metabolites (DAMs) were detected. Comprehensive bioinformatics analysis underscored significant molecular pathways in the co-enrichment of DAPs and DAMs, particularly focusing on the citrate cycle, ROS, oxidative phosphorylation, and glycine, serine, and threonine metabolism etc. We elucidated the differential impacts of AV and EE collection methods on the quality and cryotolerance of goat semen from omics perspectives, which offer a critical foundation for further exploration into optimizing semen collection and cryopreservation techniques in goat breeding program.

A review on the functional roles of trehalose during cryopreservation of small ruminant semen

Sperm cryopreservation is an approach to preserve sperm cells in liquid nitrogen or other cryogenic media for future use in assisted reproductive technologies, such as in vitro fertilization or artificial insemination. Sperm cryopreservation has been extensively used in the dairy industry and has attained excellent results after artificial insemination. However, for small ruminants the application of sperm cryopreservation is limited, due to the poor quality of frozen semen and special characteristics of the reproductive female tract. In order to improve post-thaw semen quality various cryoprotectants are used. Currently, many types of cryoprotectants, such as permeable organic solvents, sugars, antioxidants, and natural or synthetic ice blockers, have been tested on small ruminants' sperm cryopreservation. Among them, trehalose; has shown potential acting as an excellent cryoprotectant for semen freezing. While, the exact roles and action mechanisms of trehalose during cryopreservation remain unclear. In this review, we systematically summarized the present usage status, potential action mechanisms, and future application prospects of trehalose in small-ruminant sperm cryopreservation.

Revisiting the Injury Mechanism of Goat Sperm Caused by the Cryopreservation Process from a Perspective of Sperm Metabolite Profiles

Semen cryopreservation results in the differential remodeling of the molecules presented in sperm, and these alterations related to reductions in sperm quality and its physiological function have not been fully understood. Given this, this study aimed to investigate the cryoinjury mechanism of goat sperm by analyzing changes of the metabolic characteristics in sperm during the cryopreservation process. The ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) technique was performed to explore metabolite profiles of fresh sperm (C group), equilibrated sperm (E group), and frozen-thawed sperm (F group). In total, 2570 metabolites in positive mode and 2306 metabolites in negative mode were identified, respectively. After comparative analyses among these three groups, 374 differentially abundant metabolites (DAMs) in C vs. E, 291 DAMs in C vs. F, and 189 DAMs in E vs. F were obtained in the positive mode; concurrently, 530 DAMs in C vs. E, 405 DAMs in C vs. F, and 193 DAMs in E vs. F were obtained in the negative mode, respectively. The DAMs were significantly enriched in various metabolic pathways, including 31 pathways in C vs. E, 25 pathways in C vs. F, and 28 pathways in E vs. F, respectively. Among them, 65 DAMs and 25 significantly enriched pathways across the three comparisons were discovered, which may be tightly associated with sperm characteristics and function. Particularly, the functional terms such as TCA cycle, biosynthesis of unsaturated fatty acids, sphingolipid metabolism, glycine, serine and threonine metabolism, alpha-linolenic acid metabolism, and pyruvate metabolism, as well as associated pivotal metabolites like ceramide, betaine, choline, fumaric acid, L-malic acid and L-lactic acid, were focused on. In conclusion, our research characterizes the composition of metabolites in goat sperm and their alterations induced by the cryopreservation process, offering a critical foundation for further exploring the molecular mechanisms of metabolism influencing the quality and freezing tolerance of goat sperm. Additionally, the impacts of equilibration at low temperature on sperm quality may need more attentions as compared to the freezing and thawing process.

The antioxidant effects of butylated hydroxytoluene on cryopreserved goat sperm from a proteomic perspective

At present, there are few reports about the proteomics changes provoked by butylated hydroxytoluene (BHT) supplementation on cryopreserved semen in mammals. Thus, we aimed to evaluate the effects of different concentrations of BHT on goat sperm and to investigate the proteomics changes of adding BHT to cryopreserved goat (Capra hircus) sperm. Firstly, semen samples were collected from four goats, and frozen in the basic extenders containing different concentrations of BHT (0.5 mM, 1.0 mM, 2.0 mM) and a control without BHT, respectively. After thawing, the protective effects of dose-dependent replenished BHT to the freezing medium on post-thaw sperm motility, integrities of plasma membrane and acrosome, reactive oxygen species levels were confirmed, with 0.5 mM BHT being the best (B group) as compared to the control (without BHT, C group). Afterwards, TMT-based quantitative proteomic technique was performed to profile proteome of the goat sperm between C group and B group. Parallel reaction monitoring was used to confirm reliability of the data. Overall, 2,476 proteins were identified and quantified via this approach. Comparing the C and B groups directly (C vs. B), there were 17 differentially abundant proteins (DAPs) po-tentially associated with sperm characteristics and functions were identified, wherein three were upregulated and 14 were downregulated, respectively. GO annotation analysis demonstrated the potential involvement of the identified DAPs in metabolic process, multi-organism process, reproduction, reproductive process, and cellular process. KEGG enrichment analysis further indicated their potential roles in renin-angiotensin system and glutathione metabolism pathways. Together, this novel study clearly shows that BHT can effectively improve quality parameters and fertility potential of post-thawed goat sperm at the optimal concentration, and its cryoprotection may be realized through regulation of sperm metabolism and antioxidative capability from the perspective of sperm proteomic modification.

Quantitative phosphoproteomics explain cryopreservation-induced reductions in ram sperm motility

Sperm cryopreservation decreases motility, probably due to changes in protein phosphorylation. Our objective was to use quantitative phosphoproteomics for systematic comparative analyses of fresh versus frozen-thawed sperm to identify factors causing cryo-injury. Ejaculates were collected (artificial vagina) from six Dorper rams, pooled, extended, and frozen over liquid nitrogen. Overall, 915, 3382, and 6875 phosphorylated proteins, phosphorylated peptides, and phosphorylation sites, respectively, were identified. At least two modified sites were present in 57.94% of the 6875 phosphosites identified, of which AKAP4 protein contained up to 331 modified sites. There were 732 phosphorylated peptides significantly up-regulated and 909 significantly down-regulated in frozen-thawed versus fresh sperm. Moreover, the conserved motif [RxxS] was significantly down-regulated in frozen-thawed sperm. Phosphorylation of sperm-specific proteins, e.g., AKAP3/4, CABYR, FSIP2, GSK3A/B, GPI, and ODF1/2 make them potential biomarkers to assess the quality of frozen-thawed ram sperm. Furthermore, these differentially phosphorylated proteins and modification sites were implicated in cryopreservation-induced changes in sperm energy production, fiber sheath composition, and various biological processes. We concluded that abnormal protein phosphorylation modifications are key regulators of reduced sperm motility. These novel findings implicated specific protein phosphorylation modifications in sperm cryo-injury. SIGNIFICANCE: This study used phosphorylated TMT quantitative proteomics to explore regulation of epigenetic modifications in frozen-thawed ram sperm. This experiment demonstrated that ram sperm freezing affects phosphorylation site modifications of proteins, especially those related to functions such as sperm motility and energy production. Furthermore, it is important to link functions of phosphorylated proteins with changes in sperm quality after freezing and thawing, and to clarify intrinsic reasons for sperm quality changes, which is of great importance for elucidating mechanisms of sperm freezing damage. Based on these protein markers and combined with cryoprotectant design theory, it provides a theoretical basis and data reference to study sperm cryoprotectants.

An updated review on the application of proteomics to explore sperm cryoinjury mechanisms in livestock animals

This comprehensive review critically examines the application of proteomics in understanding sperm cryoinjury mechanisms in livestock animals, in the context of the widespread use of semen cryopreservation for genetic conservation. Despite its global adoption, cryopreservation often detrimentally affects sperm quality and fertility due to cryoinjuries. These injuries primarily arise from ice crystal formation, osmotic shifts, oxidative stress, and the reorganization of membrane proteins and lipids during freezing and thawing, leading to premature capacitation-like changes. Moreover, the cryopreservation process induces proteome remodeling in mammalian sperm. Although there have been technological advances in semen cryopreservation, the precise mechanisms of mammalian sperm cryoinjury remain elusive. This review offers an in-depth exploration of how recent advancements in proteomic technologies have enabled a detailed investigation into these molecular disruptions. It presents an analysis of protein-level alterations post-thaw and their impact on sperm viability and functionality. Additionally, it discusses the role of proteomics in refining cryopreservation techniques to mitigate cryoinjury and enhance reproductive outcomes in livestock. This work synthesizes current knowledge, highlights gaps, and suggests directions for future research in animal reproductive science and biotechnology.

Recent approaches in the use of antioxidants and proteomic modifications in ram semen preservation

Sperm preservation is a well-established technique in reproductive biotechnology that is widely used to maintain the genetic quality of male individuals. However, there are several factors during the preservation process that can affect the vitality, functionality, and quality of sperm, thereby reducing their fertility potential after thawing. One of these factors is the synthesis of high levels of oxidative stress (OS) during semen preservation, which can have detrimental effects on sperm health and functionality. To counter the negative impact of OS on sperm, researchers have explored the supplementation of several exogenous antioxidants in the extenders used to preserve ram sperm. This approach has shown promising results in improving sperm health, functionality, and fertility potential in ram. Additionally, the preservation process can induce modifications in the ram sperm proteome. By employing targeted proteomics techniques, researchers have been able to identify and modify specific proteins in cryopreserved ram sperm, potentially offering further improvements in the quality of the cryopreserved ram sperm. In summary, this review provides a comprehensive overview of the antioxidants and targeted proteomics modifications that have been investigated for enhancing ram sperm preservation. These advancements aim to mitigate the negative effects of OS and optimize the techniques used in preserving ram sperm.

Identification and functional analysis of differentially expressed proteins in high and low freezing tolerance sheep sperm

The purpose of this study was to identify proteins associated with differences in the freezing tolerance of sheep sperm and to analyze their functions. Qualified fresh semen from four breeds of rams, the Australian White, white-head Dorper, Black-head Dorper, and Hu sheep breeds, were selected for cryopreservation. The sperm freezing tolerance was investigated by evaluation of the overall vitality, progressive vitality, and rapidly advance vitality of the sperm. A differential model of sperm freezing tolerance was constructed for sheep breeds showing significant differences. Differentially expressed proteins associated with sperm freezing tolerance were identified using iTRAQ and the protein functions were analyzed. It was found that sperm freezing tolerance was best in Hu sheep and worst in white-head Dorper sheep. These two breeds were used for the construction of a model based on differences in freezing tolerance and the identification of sperm proteins expressed differentially before freezing and after thawing. A total of 128 differentially expressed proteins (88 up-regulated and 40 down-regulated) were identified before freezing and after thawing in Hu sheep sperm (fresh/frozen Hu sheep sperm referred to as HL vs. HF), while 219 differentially expressed proteins (106 up-regulated and 113 down-regulated) were identified in white-head Dorper sheep (fresh/frozen white-head Dorper sheep sperm referred to as WL vs. WF). A comparison of these differentially expressed proteins showed that 57 proteins overlapped between the two breeds while 71 were only expressed in Hu sheep and 162 were only expressed in white-head Dorper sheep. Functional annotation and enrichment analyses of differentially expressed proteins down-regulated in Hu sheep involved in phosphorylation of phosphatidylinositol phosphate kinases, regulation of GTPase activity and glycolysis/gluconeogenesis signaling pathway. Up-regulated proteins of Hu sheep participated in oxidoreductase activity and oxidative phosphorylation process of sperm freezing. Furthermore, down-regulated in white-head Dorper sheep involved in the metabolic regulation of carbohydrate and nuclear sugar metabolism. Up-regulated proteins of white-head Dorper sheep involved in the ferroptosis and oxidative phosphorylation pathways. Collectively, These proteins were found to participate mainly in oxidative phosphorylation as well as phosphorylation and metabolic processes in the mitochondria to affect the freezing tolerance of sheep sperm.

Proteomic analysis of high and low-motility frozen-thawed spermatozoa in yak provides important insights into the molecular mechanisms underlying sperm cryodamage

Sperm cryodamage caused by cryopreservation limits the use of frozen yak spermatozoa in artificial insemination (AI). However, the proteomic changes involved in the cryodamage of yak spermatozoa have not been investigated to date. Therefore, this study aimed to identify proteins related to freezing tolerance. Tandem mass tag (TMT) were used in combination with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for identifying differentially expressed proteins (DEPs) between high-motility (HM) and low-motility (LM) frozen-thawed yak spermatozoa. A total of 116 DEPs were identified (>1.5-fold, P < 0.05); of which, 104 proteins were upregulated in HM spermatozoa and 12 proteins were upregulated in LM spermatozoa. The results of functional annotation analysis revealed that the DEPs were mainly involved in metabolic processes. A total of 20 DEPs that were abundantly expressed in HM spermatozoa were strongly associated with carbohydrate metabolism. The results of KEGG analysis revealed that the DEPs were enriched in glycolysis/gluconeogenesis, PPAR signaling pathway, and Ras signaling pathway. In addition, many antioxidant enzymes such as superoxide dismutase (SOD1), peroxiredoxin-6 (PRDX6), and Parkinson disease protein 7 (PARK7) were upregulated in HM spermatozoa, suggesting that these enzymes affect the motility of spermatozoa by regulating the levels of reactive oxygen species (ROS) in frozen-thawed spermatozoa. Altogether, the findings of this study elucidate the mechanisms through which cryopreservation affects the movement of yak spermatozoa and offer a novel basis for refining freezing techniques and modifying cryopreservation extender components.

Comparative iTRAQ proteomics identified proteins in fresh and frozen thawed yak spermatozoa

The changes in semen and cryodamage after the cryopreservation process negatively affect sperm function and motility. However, possible proteomic alterations of yak semen during cryopreservation have not yet been achieved. In this study, we compared proteomes of fresh and frozen thawed yak sperm using iTRAQ combined with LC-MS/MS proteome approach. Totally, 2064 proteins were quantitatively identified, including 161 in fresh sperm that showed significant differences compared to frozen thawed sperm. According to the Gene ontology (GO) enrichment analysis, differentially expressed proteins (DEPs) are predominantly associated with spermatogenesis, tricarboxylic acid cycle, ATP synthesis, and differentiation biological process. Furthermore, the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that DEPs were mainly involved in metabolic pathways related to pyruvate metabolism, carbon metabolism, glycolysis/gluconeogenesis, together with the citrate (TCA) cycle. In the analysis of the protein-protein interaction (PPI) network, 15 potential proteins (PDHB, DLAT, PDHA2, PGK1, TP5C1, etc.) that could be related to the sperm quality of the yaks were obtained. Furthermore, 6 DEPs were validated by parallel reaction monitoring (PRM), confirming that the iTRAQ data were reliable. These results indicate that cryopreservation alters the proteome of yak sperm, which is possibly related to cryodamage and fertilization ability.

Integrated transcriptomics and proteomics assay identifies the role of FCGR1A in maintaining sperm fertilization capacity during semen cryopreservation in sheep

Semen cryopreservation is a promising technology employed in preserving high-quality varieties in animal husbandry and is also widely applied in the human sperm bank. However, the compromised qualities, such as decreased sperm motility, damaged membrane structure, and reduced fertilization competency, have significantly hampered the efficient application of this technique. Therefore, it is imperative to depict various molecular changes found in cryopreserved sperm and identify the regulatory network in response to the cryopreservation stress. In this study, semen was collected from three Chinese Merino rams and divided into untreated (fresh semen, FS) and programmed freezing (programmed freezing semen, PS) groups. After measuring different quality parameters, the ultra-low RNA-seq and tandem mass tag-based (TMT) proteome were conducted in both the groups. The results indicated that the motility (82.63% ± 3.55% vs. 34.10% ± 2.90%, p < 0.05) and viability (89.46% ± 2.53% vs. 44.78% ± 2.29%, p < 0.05) of the sperm in the FS group were significantly higher compared to those in the PS group. In addition, 45 upregulated and 291 downregulated genes, as well as 30 upregulated and 48 downregulated proteins, were found in transcriptomics and proteomics data separately. Moreover, three integrated methods, namely, functional annotation and enrichment analysis, Pearson's correlation analysis, and two-way orthogonal partial least squares (O2PLS) analysis, were used for further analysis. The results suggested that various differentially expressed genes and proteins (DEGs and DEPs) were mainly enriched in leishmaniasis and hematopoietic cell lineage, and Fc gamma receptor Ia (FCGR1A) was significantly downregulated in cryopreserved sperm both at mRNA and protein levels in comparison with the fresh counterpart. In addition, top five genes (FCGR1A, HCK, SLX4, ITGA3, and BET1) and 22 proteins could form a distinct network in which genes and proteins were significantly correlated (p < 0.05). Interestingly, FCGR1A also appeared in the top 25 correlation list based on O2PLS analysis. Hence, FCGR1A was selected as the most potential differentially expressed candidate for screening by the three integrated multi-omics analysis methods. In addition, Pearson's correlation analysis indicated that the expression level of FCGR1A was positively correlated with sperm motility and viability. A subsequent experiment was conducted to identify the biological role of FCGR1A in sperm function. The results showed that both the sperm viability (fresh group: 87.65% ± 4.17% vs. 75.8% ± 1.15%, cryopreserved group: 48.15% ± 0.63% vs. 42.45% ± 2.61%, p < 0.05) and motility (fresh group: 83.27% ± 4.15% vs. 70.41% ± 1.07%, cryopreserved group: 45.31% ± 3.28% vs. 35.13% ± 2.82%, p < 0.05) were significantly reduced in fresh and frozen sperm when FCGR1A was blocked. Moreover, the cleavage rate of embryos fertilized by FCGR1A-blocked sperm was noted to be significantly lower in both fresh (95.28% ± 1.16% vs. 90.44% ± 1.56%, p < 0.05) and frozen groups (89.8% ± 1.50% vs. 82.53% ± 1.53%, p < 0.05). In conclusion, our results revealed that the downregulated membrane protein FCGR1A can potentially contribute to the reduced sperm fertility competency in the cryopreserved sheep sperm.

iTRAQ-based comparative proteomics reveal an enhancing role of PRDX6 in the freezability of Mediterranean buffalo sperm

BACKGROUND

Semen cryopreservation is a critical tool for breed improvement and preservation of biodiversity. However, instability of sperm freezability affects its application. The Mediterranean buffalo is one of the river-type buffaloes with the capacity for high milk production. Until now, there is no specific cryopreservation system for Mediterranean buffalo, which influences the promotion of excellent cultivars. To improve the semen freezing extender used in cryopreservation of Mediterranean buffalo, different protein datasets relating to freezability sperm were analyzed by iTRAQ-based proteomics. This study will be beneficial for further understanding the sperm freezability mechanism and developing new cryopreservation strategy for buffalo semen.

RESULTS

2652 quantified proteins were identified, including 248 significantly differentially expressed proteins (DEP). Gene Ontology (GO) analysis indicated that many these were mitochondrial proteins, enriched in the molecular function of phospholipase A2 activity and enzyme binding, and biological processes of regulation of protein kinase A signaling and motile cilium assembly. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis identified 17 significant pathways, including oxidative phosphorylation (OXPHOS). Furthermore, 7 DEPs were verified using parallel reaction monitoring or western blot, which confirmed the accuracy of the iTRAQ data. Peroxiredoxin 6 (PRDX6), which expressed 1.72-fold higher in good freezability ejaculate (GFE) compared to poor freezability ejaculate (PFE) sperms, was selected to explore the function in sperm freezability by adding recombinant PRDX6 protein into the semen freezing extender. The results showed that the motility, mitochondrial function and in vitro fertilization capacity of frozen-thawed sperm were significantly increased, while the oxidation level was significantly decreased when 0.1 mg/L PRDX6 was added compared with blank control.

CONCLUSIONS

Above results revealed the metabolic pattern of freezability of Mediterranean buffalo sperms was negatively associated with OXPHOS, and PRDX6 had protective effect on cryo-damage of frozen-thawed sperms.

Expression of TXNRD1, HSPA4L and ATP1B1 Genes Associated with the Freezability of Boar Sperm

Cryopreservation is associated with increased oxidative stress, which is responsible for sperm damage. We analyzed the effect of cryopreservation on mRNA and protein expression of thioredoxin reductase 1 (TXNRD1), heat shock protein family A (HSP 70) member 4 like (HSPA4L) and sodium/potassium-transporting ATPase subunit beta-1 (ATP1B1) genes in boar sperm with different freezability. Boars were classified as having good and poor semen freezability (GSF and PSF, respectively), according to the assessment of post-thaw sperm motility. Total RNA was isolated from fresh pre-freeze (PF) and frozen-thawed (FT) sperm from five boars of the GSF and PSF groups, respectively. Quantification of TXNRD1, HSPA4L and ATP1B1 gene expression was performed by RT-qPCR analysis. Proteins extracted from sperm were subjected to Western blotting and SDS-PAGE analyses. Poor freezability ejaculates were characterized by significantly higher relative mRNA expression levels of TXNRD1 and HSPA4L in FT sperm compared with the fresh PF sperm. Furthermore, the relative mRNA expression level of ATP1B1 was significantly higher in the fresh PF sperm of the GSF group. Western blotting analysis revealed significantly higher relative expression of TXNRD1 protein in the fresh PF sperm of the GSF group, while HSPA4L protein expression was markedly increased in FT sperm of the PSF group. Electrophoretic and densitometric analyses revealed a higher number of proteins in the fresh PF and FT sperm of the PSF and GSF groups, respectively. The results of this study indicate that ATP1B1 mRNA expression in the fresh PF sperm is a promising cryotolerance marker, while the variations of TXNRD1 and HSPA4L protein expression in the fresh PF or FT sperm provide useful information that may help to elucidate their biological significance in cryo-damage.