Proteomic identification of seminal plasma proteins related to the freezability of carp semen.

Unlabelled: The variation in sperm freezability among individuals within a fish species is a major factor justifying the identification of useful predictive indicators of cryopreservation success. It is unknown at present whether the protein composition of fish seminal plasma affects sperm freezability. Therefore, the aims of this study were to compare the proteome of carp seminal plasma from semen rated as good (GF) and poor (PF) freezability by two-dimensional difference gel electrophoresis followed by MALDI-TOF/TOF mass spectrometry. The semen was classified as GF and PF based on sperm motility assessment after freeze/thawing. Five spots representing three proteins were more abundant in GF, while ten spots representing seven proteins were more abundant in PF seminal plasma. The majority of proteins present in higher abundance in PF seminal plasma were associated with the innate immune response. On the other hand, higher freezability was associated with proteins involved in the maintenance of sperm membrane integrity and antioxidative protection. These results indicate that carp semen freezability levels may be related to different seminal plasma protein profiles. Lower usefulness of spermatozoa in cryopreservation may be related to previous infection or stress leading to sublethal changes to sperm structure.

Significance: Sperm quality parameters such as motility, viability and sperm concentration have been used as predictive tools of sperm cryopreservation potential in fish species However, the usefulness of initial motility parameters as indicators of freezability varies among fish species and between individuals within a species. Recent studies in mammals revealed that male-to-male variability in cryoresistance can be attributed to differences in seminal plasma protein composition. To the best of our knowledge, no proteomic studies linking the protein composition of fish seminal plasma and freezing resilience have been performed in fish. Our results indicate for the first time that factors regulating how carp semen tolerate cryopreservation may be related to the different protein profiles of carp seminal plasma. The obtained results provide new insight into understanding the molecular mechanisms underlying cryoresistance of carp semen and provide a tool for the improvement of a long-term sperm preservation procedure.