Poly-ubiquitinated proteins and proteasomes distribution in human spermatogenesis and severe teratozoospermia

MC BRANZINI,; C WÓJCIK,; H CHEMES,; V RAWE

Washington DC, USA

Congreso; Congreso Anual de la ASRM; 2007

ASRM: American Society of Reproductive Medicine

Objective: The purpose of spermatogenesis is to generate a large number of competent sperm for fertilization. To attain specialized functions and appropriate morphology, most of spermatid cytoplasm is eliminated and chromatin suffers rearrangements. The proteasome-ubiquitin system is known to be involved in the nuclear histone-TP- protamine transition but its significance in normal and abnormal human spermatogenesis is poorly understood. We analyzed the distribution of proteasomes and poly-ubiquitinated proteins (pUP) in normal human ejaculated sperm and testicular spermatogenic cells from fertile individuals and ejaculated sperm from a patient with severe teratozoospermia previously diagnosed with chromatin immaturity by electron microcopy. Materials and methods: Normal and abnormal spermatozoa and immature spermatogenic cells were analyzed using immunocytochemistry and transmission electron microscopy. Monoclonal and polyclonal antibodies reactive against the ab proteasomes, p31 (proteasome regulatory core) and FK1 (polyubiquitinated proteins) were used. Cells were examined under epifluorescence and electron microscope. Images were edited with Adobe Photoshop 7.0. Results: We found fluctuations of pUP and proteasome expression levels during spermatogenesis. In the nuclei of human spermatids, pUP co-localized with proteasomes (p31). In mature testicular sperm p31 is associated with the acrosome and the connecting piece. ab proteasomes localized to the nuclei and cytoplasm of immature spermatogenic cells but drifs away from the nucleus during elongation-compaction and is subsequently lost with the residual body at spermiation. In normal ejaculated spermatozoa, pUP appeared only associated to the mitochondrial sheath. Conversely, in the teratozoospermic patient, a significant percentage of ejaculated spermatozoa (p<0.05) displayed an important nuclear pUP signal. Conclusions: Our results show that pUP are present at different stages of germ cell maturation and are degraded by the ubiquitin-proteasome system during chromatin remodeling events (histone-TP-protamin transition) that result in chromatin condensation. Their elevated presence inside abnormal teratozoospermic sperm nuclei, provides preliminary indications that human sperm poly-ubiquitination plays a role in teratozoospermia and negatively correlates with normal nuclear condensation. The accumulation of 19S subunits in the acrosome and connecting piece is linked to essential maturation and fertilization events.