A SEARCH FOR SEX-SPECIFIC ANTIGENS ON BOVINE SPERMATOZOA USING IMMUNOLOGICAL AND BIOCHEMICAL TECHNIQUES TO COMPARE THE PROTEIN PROFILES OF X-CHROMOSOME-BEARING AND Y-CHROMOSOME-BEARING SPERM POPULATIONS SEPARATED BY FLUORESCENCE-ACTIVATED CELL SORTING

Currently, the only successful method for separating X and Y chromosom e-bearing spermatozoa is fluorescence-activated cell sorting. Although effective, this technique is of limited usefulness to the animal bree ding industry as it cannot produce the large volumes of sexed spermato zoa needed for artificial insemination. An attractive alternative woul d be to identify an immunological marker confined to one sperm type an d, therefore, significant scientific effort has been expended in exami ning antibodies that appear to recognize approximately 50% of spermato zoa in an ejaculate. However, no sex-specific antigens have yet been i dentified from spermatozoa. Using the opportunity afforded by the deve lopment of sperm separation by fluorescence-activated cell sorting, we have made a thorough search for differences between X and Y chromosom e-bearing bull spermatozoa using both biochemical and immunological me thods. Techniques for radiolabelling surface membrane proteins, in con junction with SDS-PAGE, failed to show any differences between populat ions. Similarly, a wide range of monoclonal antibodies raised to ejacu lated, cauda epididymidal and testicular spermatozoa failed to disting uish between the X and Y chromosome-bearing spermatozoa. Only after an alysis by high resolution two-dimensional SDS-PAGE was an indication o btained that X-specific proteins occur. However, these proteins are no t associated with the surface membrane and further work is necessary t o confirm their association with the X chromosome and to characterize them more fully. Our inability to detect sex-specific differences in s perm surface antigenicity suggests that further work on this immunolog ical approach to semen sexing is unlikely to be profitable.