Characteristics of bull sperm acrosome associated 1 proteins

⬢SPACA1 proteins are the sperm biomarkers for predicting bull AI-subfertility.⬢Distribution of SPACA1 proteins is arranged during epididymal sperm maturation.⬢Epididymal abilities to arrange their distribution showed individual differences.⬢They showed characteristics of the membrane raft-associated proteins.⬢Relation between bull AI-subfertility and epididymal dysfunctions was discussed. An atypical distribution of sperm acrosomal tyrosine-phosphorylated proteins [which include sperm acrosome associated 1 (SPACA1) proteins] may be related to the relatively lesser pregnancy rates when semen of some bulls are used for artificial insemination (AI). There may also be these associations with bull SPACA1 proteins that are translocated from the equatorial segment to the anterior part in the acrosomes during sperm maturation in the normally functioning epididymis. The aim of the present study, therefore, was assessment of the characteristics of bull SPACA1 proteins. Results from immunocytochemical evaluations indicate there were large variations in sperm percentages with typically distributed SPACA1 proteins in acrosomes of cauda epididymal sperm samples (7%–95%). These values were positively correlated with percentages of epididymal spermatozoa with typically distributed acrosomal tyrosine-phosphorylated proteins (r=0.8564, P