The role of sperm proteasomes during sperm aster formation and early zygote development: implications for fertilization failure in humans

Abstract

BACKGROUND Sperm aster organization during bovine and human fertilization requires a paternally-derived centriole that must first disengage from the sperm tail connecting-piece. We investigated the participation of the 26S proteasome in this process. METHODS Proteasome localization and enzymatic activity were studied in normal and pathological human spermatozoa by immunocytochemistry and enzyme-substrate assays. The role of proteasomes during bovine zygote development was investigated using a pharmacological proteasome-inhibitor, MG132, and with anti-proteasome antibodies delivered by Streptolysin O-permeabilization or with the Chariot reagent. Human zygotes discarded after ICSI failures (n = 28) were also examined. RESULTS Proteasomes were localized in the sperm acrosome and connecting-piece, as well as in the pronuclei of bovine and human zygotes. Proteasomal enzymatic activities were decreased in defective human spermatozoa. Disrupted sperm aster formation and pronuclear development were found after pharmacological and immunological block of proteasomes in human/bovine spermatozoa and oocytes, as well as in 28 discarded human post-ICSI fertilization failures. CONCLUSIONS Specific proteasome inhibition disrupts sperm aster formation and pronuclear development/apposition in bovine and human zygotes. Human spermatozoa with defective centriolar/pericentriolar structures have decreased proteasomal enzymatic activity. Release of a functional sperm centriole that acts as a zygote microtubule-organizing center probably relies on selective proteasomal proteolysis. These findings suggest an important role of sperm proteasomes in zygotic development.

Genome wide identification of promoter binding sites for H4K12ac in human sperm and its relevance for early embryonic development

“…This is in agreement with mRNA fingerprints differing substantially between normospermic and teratozoospermic men. 26,27 These findings support the idea that aberrant histone modifications may be associated with impaired expression of developmentally important mRNA transcripts in teratozoospermic men, the fertilization capacity. The routine ejaculate diagnostic provides evidence of the variability between healthy individuals, although those men exhibit all normal sperm parameters, according to the WHO guidelines.…”

Proteomic comparison of detergent-extracted sperm proteins from bulls with different fertility indexes

“…Immunofluorescence assays localised proteasome in the acrosomal region in all species studied (Rawe et al 2008). Although some discrepancies across species are reported, all studies report an implication of proteasome in events related to the acrosomal reaction (Morales et al 2003, Sutovsky et al 2004, Rawe et al 2008. Proteasomes have also been detected at the connecting piece between head and tail in bovine and human sperm (Wojcik et al 2000, Rawe et al 2008.…”

“…Proteasome activity has been detected in sperm from many mammals, including bovine and human (Pizarro et al 2004). Immunofluorescence assays localised proteasome in the acrosomal region in all species studied (Rawe et al 2008). Although some discrepancies across species are reported, all studies report an implication of proteasome in events related to the acrosomal reaction (Morales et al 2003, Sutovsky et al 2004, Rawe et al 2008.…”

“…Although some discrepancies across species are reported, all studies report an implication of proteasome in events related to the acrosomal reaction (Morales et al 2003, Sutovsky et al 2004, Rawe et al 2008. Proteasomes have also been detected at the connecting piece between head and tail in bovine and human sperm (Wojcik et al 2000, Rawe et al 2008. It has been suggested that they play different roles during the post-fertilisation disassembly of the sperm tail connecting piece, sperm aster formation, pronuclear development and apposition (Rawe et al 2008).…”

Sperm macrocephaly syndrome in a patient without AURKC mutations and with a history of recurrent miscarriage

“…This is likely related to the absence of multi-tailed spermatozoa: although macro-cephalic, mono-centriolar spermatozoa allow the formation of a single meiotic aster, and consequently even if a sper-matozoon is dysomic or diploid, two pronuclei are seen in the zygotes ( Rawe et al, 2008). The spontaneous miscar-riage that always followed conception was the unavoidable consequence of a severe sperm aneuploidy.…”