Immunodetection of Tau microtubule-associated protein in human sperm and testis

primary antibody was omitted. The slides were observed, and images were acquired with a confocal LSM710 microscope and an Axioplan microscope (both from Zeiss, Göttingen, Germany). Tau immunostaining was detected in all smeared spermatozoa (Figure 1a). The Tau protein was located in the sperm midpiece. In testicular tissue, Tau immunoreactivity was observed in both spermatocytes and spermatids (Figure 1b). In spermatocytes, cytoplasmic f luorescent dots were located all around the nucleus (Figure 1c). In elongated spermatids, the immunolabeled zone was situated behind the nucleus (Figure 1d). No staining was observed in spermatozoa or in tissue sections of control samples lacking primary antibody (Figure 1e and 1f). Over the last decades, few researchers have studied the presence of Tau protein in the reproductive tract. Two eminent, early studies reported the presence of Tau protein in the rodent and bovine testis.4,5 In human germ cells and spermatozoa, Tau may be involved in the regulation of microtubule proteins. The spermatozoon’s main microtubule-organizing centre is the centrosome complex. It has a role in sperm and zygote aster formation, and the development of the bipolar mitotic apparatus.7 Dysfunction of the centrosome complex will result in developmental abnormalities after fertilization. The epithelium of seminiferous tubules has a vast network of microtubules (particularly within the manchette, the axoneme, and the mitotic and meiotic spindles of germ cells).8 The presence of Tau in human testicular tissue suggests that this protein has a role in meiotic division in male germ cells and during their extension to spermatozoa. As has been suggested in the context of tauopathies,9 the aggregation, hyperphosphorylation and/or ubiquination of Tau might impair sperm microtubule function and transport. In summary, this study reports the immunoexpression of Tau microtubule-associated protein in human sperm and testis. We hypothesize that Tau is involved in the development of sperm in a man and thus may represent an additional parameter for sperm function in male fertility.