Characterization of tetraspanin protein CD81 in mouse spermatozoa and bovine gametes

Abstract

Sperm-egg interaction and fusion represent a key moment of fertilization. In mammals, it is not possible without the interaction of the tetraspanin superfamily proteins including CD81. A detailed immunohistochemical localization of CD81 was monitored in bovine oocytes during different maturation stages, as well as during early embryogenesis. In addition, characterization of CD81 was carried out in bovine and mouse sperm. In bovine eggs, CD81 was detected on the plasma membrane of the germinal vesicle, metaphase I and metaphase II oocytes. During fertilization, accumulation of CD81 molecules in the perivitelline space of fertilized oocytes, which appeared as vesicles associated with plasma membrane, was observed. In majority of bull-ejaculated sperm and caput, corpus and cauda epididymal sperm, as well as mouse cauda epididymal sperm, CD81 was found on the plasma membrane covering the apical acrosome. Although the process of capacitation did not influence the localization of CD81, it was lost from the surface of the acrosome-reacted spermatozoa in bull, in contrast to mouse sperm where there was a relocalization of the CD81 protein during acrosome reaction across the equatorial segment and later over the whole sperm head. The presented results highlight conservative unifying aspects of CD81 expression between cattle and mouse, together with mouse-specific traits in sperm CD81 behaviour, which emphasizes certain species-specific mechanisms of fertilization to be considered.

Expression and distribution of CD151 as a partner of alpha6 integrin in male germ cells

“…There is a remarkable consistence in our results among studied species when we describe CD151 protein expression in germ cells during their development and consequent maturation stages including the protein detection after the AR. From our previous finding on tetraspanins CD9 and CD81, their characteristic pattern to some extent differed between mouse, bull and human and retained its species specific uniqueness 12,13,35 . However, in mouse and human, CD9 location in the equatorial segment after the AR stands out 13 , similarly to our current results, CD151 is destined to this sperm primary fusogenic region.…”

“…During this event, many of the membrane proteins originally locked in the acrosome relocate to the plasma membrane and different sperm head compartments, mainly to the equatorial segment. This re-location process was previously describe for proteins that are key players of gamete fusion such as Izumo1 30,34 , CD46 and integrins 32 or tetraspanin CD81 and CD9 13,35 . Structural modelling of CD9 and CD81 interaction in human sperm 13 suggested the possible role for CD81 as a regulator of dynamic changes in sperm plasma membrane, whereas CD9 appeared to be involved in web stabilization and mediation of trans protein binding upon sperm-egg interactions 13 .…”

“…It is of relevance that namely CD81 and CD151 www.nature.com/scientificreports www.nature.com/scientificreports/ are reported to be a crosslink mediating indirect interaction of integrins with other tetraspanins 24,47 . These membrane cis protein interactions are of importance for "outside-in" signalization, reported from the somatic cells 48,49 as well as playing their role within female gametes 10,14,22 . However, CD151 is known to participate with the α6β1 integrin in the formation of a functional complex involved in human sperm-egg fusion 22 .…”

“…Tetraspanin CD9 expressed on mouse eggs is considered as an essential molecule for successful gamete fusion 7-9 as well as tetraspanin CD81 which is also involved in fertilization 10,11 . Our previous studies concerning species-specific traits of CD9 and CD81 in mouse, bull and porcine gametes during their functional maturation and fertilization, suggested the active participation of tetraspanins in these events [11][12][13][14] . With the ability of tetraspanins being part of signalling cascades involving cytoskeleton 5,15,16 they also play a crucial role in the organization of functional membrane protein cluster domains called a tetraspanin web, which were also described in oocyte and recently in sperm.…”

FGF10 enhances yak oocyte fertilization competence and subsequent blastocyst quality and regulates the levels of CD9, CD81, DNMT1, and DNMT3B

“…The expression of CD9, CD81, DNMT1, and DNMT3B promotes sperm–oocyte interactions (Antalíková et al ) and the maintenance or de novo methylation processes during fertilization (Uysal et al ). In our present study, the maturation rates of yak oocytes and total spermatozoa motility were improved by FGF10, and the levels of CD9, CD81, DNMT1, and DNMT3B in oocyte maturation and spermatozoa were also regulated by FGF10, which helped to sperm–oocyte fusion (Antalíková et al ; Jankovicova et al ; Y. H. Li et al ; Ohnami et al ; Uysal et al , ). The cleavage rate after IVF was highest in the group treated with 5 ng/ml FGF10 during both IVM and capacitation (Table ), which also showed the highest levels of CD9, CD81, DNMT1, and DNMT3B in mature COCs and capacitated sperms (Figures and ).…”