The identification of proteomic markers of sperm freezing resilience in ram seminal plasma.

The source and composition of seminal plasma has previously been shown to alter the ability of spermatozoa to survive cryopreservation. In the present study, the ionic and proteomic composition of seminal plasma from rams with high (HSP; n = 3) or low (LSP; n = 3) freezing resilient spermatozoa was assessed. 75 proteins were identified to be more abundant in HSP and 48 proteins were identified to be more abundant in LSP. Individual seminal plasma proteomes were established for each of the six rams examined. For each ram, correlations were conducted between previously recorded freezing resilience [1] and individual spectral counts in order to identify markers of freezing resilience. 26S proteasome complex, acylamino acid releasing enzyme, alpha mannosidase class 2C, heat shock protein 90, tripeptidyl-peptidase 2, TCP-1 complex, sorbitol dehydrogenase and transitional endoplasmic reticulum ATPase were found to be positively correlated (r(2) > 0.7) with freezing resilience. Cystatin, zinc-2-alpha glycoprotein, angiogenin-2-like protein, cartilage acidic protein-1, cathepsin B and ribonuclease 4 isoform 1 were found to be negatively correlated (r(2) > 0.7) with freezing resilience. Several negative markers were found to originate from the accessory sex glands, whereas many positive markers originated from spermatozoa and were part of or associated with the 26S proteasome or CCT complex.