Presence of acetylated α-tubulin in human sperm nuclei: A contributor to sperm heterogeneity

The global rise in male infertility necessitates a constant search for underlying causes, diagnostics and corrective treatments. Sperm cells are irreplaceable cells for the process of reproduction. Intrauterine insemination (IUI) is a simple and non-invasive technique, most commonly used to overcome both unexplained and mild male-factor infertility. Even though spermatozoa may be classified as “normal” in terms of morphology, motility and concentration, they could be defective at the subcellular level. Protein lysine acetylation within human sperm, a major post-translational modification of tubulin, is suspected to be a cause of sperm abnormality but is not fully understood. An examination of α-tubulin and acetylated α-tubulin immunopresence, spatial distribution and co-localisation in normozoospermic and asthenozoospermic semen samples was conducted to determine if acetylated α-tubulin could be a biomarker of sperm heterogeneity to better predict sperm fertility potential for IUI outcome. Acetylated α-tubulin was present in both sperm subcompartments, tail and nucleus of normozoospermic samples. We found more immunopositivity for acetylated α-tubulin in the sperm tail and less in nucleus of asthenozoospermic compared to normozoospermic samples. Hence, the acetylated α-tubulin in sperm may contribute to sperm nuclei heterogeneity and serve as a novel molecular biomarker.