Differential surface glycoprofile of buffalo bull spermatozoa during mating and non-mating periods

The buffalo has a seasonal reproduction activity with mating and non-mating periods occurring from late autumn to winter and from late spring to beginning of autumn, respectively. Sperm glycocalyx plays an important role in reproduction as it is the first interface between sperm and environment. Semen quality is poorer during non-mating periods, so we aimed to evaluate if there were also seasonal differences in the surface glycosylation pattern of mating period spermatozoa (MPS) compared with non-mating period spermatozoa (NMPS). The complexity of carbohydrate structures makes their analysis challenging, and recently the high-throughput microarray approach is now providing a new tool into the evaluation of cell glycosylation status. We adopted a novel procedure in which spermatozoa was spotted on microarray slides, incubated with a panel of 12 biotinylated lectins and Cy3-conjugated streptavidin, and then signal intensity was detected using a microarray scanner. Both MPS and NMPS microarrays reacted with all the lectins and revealed that the expression of (i) O-glycans with NeuNAcα2-3Galβ1,3(±NeuNAcα2-6)GalNAc, Galβ1,3GalNAc and GalNAcα1,3(l-Fucα1,2)Galβ1,3/4GlcNAcβ1 was not season dependent; (ii) O-linked glycans terminating with GalNAc, asialo N-linked glycans terminating with Galβ1,4GlcNAc, GlcNAc, as well as α1,6 and α1,2-linked fucosylated oligosaccharides was predominant in MPS; (iii) high mannose- and biantennary complex types N-glycans terminating with α2,6 sialic acids and terminal galactose were lower in MPS. Overall, this innovative cell microarray method was able to identify specific glycosylation changes that occur on buffalo bull sperm surface during the mating and non-mating periods.