HVCN1 but Not Potassium Channels Are Related to Mammalian Sperm Cryotolerance

Genome-wide discovery of underlying genetic factors associated with fresh and frozen-thawed semen traits in composite ram breeds exhibiting different cryotolerance

Fewer studies investigate the effects of underlying genetic factors related to semen characteristics, significantly affecting sheep farm profitability. This study aimed to identify single nucleotide polymorphisms (SNP) and genomic regions associated with fresh and frozen-thawed semen traits in rams with low (Hasak) and high (Hasmer) cryotolerance. Semen collected from 11 (5 Hasak with low and 6 Hasmer with high cryotolerance) rams cryopreserved in 0.25 ml straws in the breeding season. Quality characteristics were determined in fresh, equilibrated, and frozen-thawed semen. A Genome-Wide Association Study (GWAS) was conducted to unveil the genetic structure that might be attributed to cryotolerance in low and high cryotoleranced rams. Fresh (regarding total and progressive motility) and equilibrated semen quality were similar in Hasak and Hasmer rams (p > 0.6). However, the freeze-thawing process had a more pronounced negative effect on ram semen traits in Hasak than in Hasmer (p < 0.05). GWAS revealed 27 SNPs correlated with post-thaw semen parameters. Moreover, network analyses revealed pathways related to sperm ion channels and their activities, providing insights into the intricate molecular mechanisms underlying sperm physiology and emphasizing their role in potentially impacting sperm cryotolerance. The functional significance of detected SNPs and the associated pathways require further exploration.

Insights into crucial molecules and protein channels involved in pig sperm cryopreservation

Cryopreservation is the most efficient procedure for long-term preservation of mammalian sperm; however, its use is not currently dominant for boar sperm before its use for artificial insemination. In fact, freezing and thawing have an extensive detrimental effect on sperm function and lead to impaired fertility. The present work summarises the basis of the structural and functional impact of cryopreservation on pig sperm that have been extensively studied in recent decades, as well as the molecular alterations in sperm that are related to this damage. The wide variety of mechanisms underlying the consequences of alterations in expression levels and structural modifications of sperm proteins with diverse functions is detailed. Moreover, the use of cryotolerance biomarkers as predictors of the potential resilience of a sperm sample to the cryopreservation process is also discussed. Regarding the proteins that have been identified to be relevant during the cryopreservation process, they are classified according to the functions they carry out in sperm, including antioxidant function, plasma membrane protection, sperm motility regulation, chromatin structure, metabolism and mitochondrial function, heat-shock response, premature capacitation and sperm-oocyte binding and fusion. Special reference is made to the relevance of sperm membrane channels, as their function is crucial for boar sperm to withstand osmotic shock during cryopreservation. Finally, potential aims for future research on cryodamage and cryotolerance are proposed, which might be crucial to minimise the side-effects of cryopreservation and to make it a more advantageous strategy for boar sperm preservation.

Sperm plasma membrane ion transporters and male fertility potential: A perspective under the prism of cryopreservation

Intracellular calcium homeostasis plays a crucial role in spermatozoa by regulating physiological functions associated with sperm quality and male fertility potential. Intracellular calcium fine balance in the sperm cytoplasm is strictly dependent on sperm surface channels including the CatSper channel. CatSpers' role is to ensure the influx of extracellular calcium, while intracellular pH alkalinization serves as a stimulus for the activation of several channels, including CatSper. Overall, the generation of intracellular calcium spikes through CatSper is essential for fertilization-related processes, such as sperm hyperactivation, acrosome reaction, egg chemotaxis, and zona pellucida penetration. Multiple lines of evidence suggest that disruption in the close interaction among ions, pH, and CatSper could impair male fertility potential. In contemporary times, the growing reliance on Medically Assisted Reproduction procedures underscores the impact of cryopreservation on gametes. In fact, a large body of literature raises concerns about the cryo-damages provoked by the freeze-thawing processes, that can affect the plasma membrane integrity, thus the structure of pivotal ion channels, and the fine regulation of both intracellular calcium and pH. This review aims to provide an overview of the importance of the CatSper channel in sperm quality and further fertilization potential. Additionally, it addresses the emerging issue of cryopreservation's impact on the functionality of this sperm channel.

Ion Channels of Spermatozoa: Structure, Function, and Regulation Mechanisms

Ion transport is essential for sperm physiology, being involved in sperm-cell differentiation and maturation, motility activation, chemotaxis towards the oocyte, and fertilization, as well as in sperm adaptation to the surrounding medium [...].