Title: Characterizing the Glycocalyx of Poultry Spermatozoa: II. Low Temperature Storage of Turkey Semen and Sperm Mobility Phenotype Impact the Carbohydrate Component of Membrane Glycoconjugates
Submitted to: Journal of Andrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 20, 2007
Publication Date: July 1, 2008
Citation: Pelaez, J. Long, J.A. 2008. Characterizing the glycocalyx of poultry spermatozoa: II. In vitro storage of Turkey semen and mobility phenotype affects the carbohydrate component of sperm membrane glycoconjugates. Journal of Andrology. 29:431-9.
Interpretive Summary: Commercial turkey producers would benefit from the capability of using semen that has been stored for 24 to 48 hours after collection from the male. Current methodology for storing turkey semen does not provide the fertility rates necessary for profitability. Our research is focused on learning why and how turkey sperm lose functional competence during in vitro storage. We have recently identified the carbohydrates present on the surface of the turkey sperm membrane. In this study, our objective was to determine if these carbohydrates are altered during in vitro semen storage. Additionally, we evaluated males of high quality and marginal quality semen (in terms of sperm movement) for differences in membrane surface carbohydrates during semen storage. We found several differences that have implications for the reduced fertility of stored turkey semen.
The turkey sperm glycocalyx is known to contain residues of sialic acid, alpha-mannose/alpha-glucose, alpha- and beta-galactose, alpha-fucose, alpha- and beta-N-acetyl-galactosamine, monomers and dimers of N-acetyl-glucosamine and N-acetyl-lactosamine. Potential changes in these carbohydrates during in vitro semen storage at 4 degrees celsius were evaluated using males of both high and low sperm mobility phenotype. Changes in carbohydrate residues were quantified by flow cytometry analysis using a battery of 14 FITC-labeled lectins in combination with control (sialylated) or neuraminidase-treated (non-sialylated) sperm. Sperm were evaluated at 0, 2, 4, 8, 12 and 24 h of storage. For control sperm, 4 different patterns of lectin binding were observed over time: 1) increased mean fluorescence intensity (MnFI) at 2h (GS-I) and 8h (RCA-I) that remained elevated during storage; 2) increased MnFI at specific time-points (LFA, 2h; jacalin, sWGA, 8h; GNA, sWGA, 12h) followed by decreasing MnFI during the remainder of the 24h storage period; 3) increased MnFI only at the 24h time-point (lotus, PNA); and 4) no changes in MnFI during the 24h storage period (ECA, GS-II, PSA, SBA, WFA). For non-sialylated sperm, increased binding of lectins ECA, GS-II, SBA and WFA were observed at variable time-points; only PSA remained unchanged. Differences between mobility phenotypes existed for lectins Con A, GS-II, LFA, PSA, SBA and sWGA, with the majority of these lectins having higher MnFI in low mobility semen during the entire storage period. We conclude that the increased rate of lectin binding reveals an augmentation of non-sialylated terminal residues that could modify the sperm antigenicity and negatively impact fertility. The semen of low-mobility males might also have higher antigenicity even before storage. Other possible functional implications are discussed.