Loss of protein kinase 2 subunit alpha 2 (CK2α') effect ram sperm function after freezing and thawing process

Protein kinase 2 subunit alpha 2 (CK2α'), a serine/threonine-selective protein kinase, is associated with sperm apoptosis. However, the presence of CK2α' in ram sperm during the freezing-thawing process has not been previously reported. Thus, this study was conducted to determine the effect of cryopreservation on the association between CK2α' and ram sperm function. Sperm variables, including sperm motility, DNA damage and acrosome integrity, were measured in fresh (F), cooled (CO) and freeze-thawed (FT) sperm. Sperm proteins and total mRNA were extracted form cells of each group, and subjected to western blot and real-time PCR analysis for detection of CK2α' proteins and relative abundance of mRNA. The distribution pattern of CK2α' protein in ram sperm was also monitored in each group using an immunofluorescence technique. The results provided evidence that the freeze-thaw process has an impact on ram sperm variables, and the normalized CK2α' protein and relative abundance of CK2α' mRNA were both significantly less in FT than F sperm. The amount of CK2α' in FT extended seminal plasma was increased as compared with F samples. Furthermore, immunofluorescence revealed that CK2α' was distributed throughout the acrosome of ram sperm. The association of CK2α' with DNA damage and acrosome integrity was confirmed using Pearson's linear correlation. In conclusion, the understanding the molecular effects of cryopreservation on CK2α' in ram sperm could provide insight into methods for improving fertility associated with frozen-thawed ram sperm.