A comparison of human spermatozoa immunolabeling features using xenogenic reagents for centrosomal proteins.

The centrosome is an organelle essential to proper chromosomal migration and normal cell growth. In the human, the centrosome is comprised of two centrioles and the pericentriolar cytosol; its control of embryo cleavage processes derives from its role as a locus for spindle organisation. At fertilisation, it is the human sperm centrosome that is responsible for ordering these processes, as the oocyte appears not to contain working centrosomal structures. Abnormalities in fertilisation or early embryo cleavage could be related to impaired sperm centrosome structure or function in some cases. While potential future treatments of infertility due to a defective centrosome could involve use of a donor centrosome to restore normal cell development, such an approach would depend on accurate localisation of this organelle for subsequent transplantation. To locate centrosomal components in the heads and tails of human spermatozoa, labeling was performed on intact spermatozoa using antibodies of known specificity to highly-conserved centrosomal elements. Following general mapping of immunofluorescent signals, unlabeled sperm were dissected to form head/tail sperm fragments which were then separately tested. Distribution of centrosomal proteins in head and tail fragments was assayed for each separation method. Three reagents were compared: 1) rabbit anti-mitotic spindle protein (anti-MSP) antibody, 2) rabbit polyclonal centriole-specific antibodies, and 3) mouse monoclonal anti-MPM-2 (a centrosome phospoprotein) antibody. Of these, anti-MPM-2 antibody appeared to be the most reliable, labeling centrosomal elements in 63% (n = 1,386) of treated spermatozoa. Sequential utilization of n-butylamine to effect head/tail separation followed by anti-MPM-2 antibody labeling was a satisfactory method of centrosome localisation. Microextraction of centrosomes and pericentriolar matrix identified by this method awaits further testing.