Abstract
The present study investigated the seminal plasma proteome of Holstein bulls with low (LF; n = 6) and high (HF; n = 8) sperm freezability. The percentage of viable frozen-thawed sperm (%ViableSperm) determined by flow cytometry varied from -2.2 in LF to + 7.8 in HF bulls, as compared to the average %ViableSperm (54.7%) measured in an 860-sire population. Seminal proteins were analyzed by label free mass spectrometry, with the support of statistical and bioinformatics analyses. This approach identified 1,445 proteins, associated with protein folding, cell–cell adhesion, NADH dehydrogenase activity, ATP-binding, proteasome complex, among other processes. There were 338 seminal proteins differentially expressed (p < 0.05) in LF and HF bulls. Based on multivariate analysis, BSP5 and seminal ribonuclease defined the HF phenotype, while spermadhesin-1, gelsolin, tubulins, glyceraldehyde-3-phosphate dehydrogenase, calmodulin, ATP synthase, sperm equatorial segment protein 1, peroxiredoxin-5, secretoglobin family 1D and glucose-6-phosphate isomerase characterized the LF phenotype. Regression models indicated that %ViableSperm of bulls was related to seminal plasma peroxiredoxin-5, spermadhesin-1 and the spermadhesin-1 × BSP5 interaction (R2 = 0.84 and 0.79; p < 0.05). This report is the largest dataset of bovine seminal plasma proteins. Specific proteins of the non-cellular microenvironment of semen are potential markers of sperm cryotolerance.
Highlights
The present study investigated the seminal plasma proteome of Holstein bulls with low (LF; n = 6) and high (HF; n = 8) sperm freezability
The three Binder of Sperm proteins (BSPs) (BSP1, BS3 and BSP5) accounted for 22.57% and spermadhesins made 14.08% of the bovine seminal plasma proteome deciphered by MuDPIT
The analysis of bovine seminal plasma conducted in the present study relied on multidimensional protein identification technology and tools of bioinformatics
Summary
Freezing and thawing semen interferes with the structure of the sperm membranes, alters functions of membrane proteins and ion channels, causes premature capacitation and acrosome reaction and yields excessive reactive oxygen species[5]. Cryopreservation reduces both sperm metabolism and mitochondrial activity and alters sperm chromatin structure[6]. All these effects result in lower motility and fertilizing capacity of frozen-thawed sperm when compared to untreated cells. The present study was aimed at uncovering the protein signatures of seminal plasma from bulls with contrasting phenotypes associated with frozen-thawed sperm viability
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