Interférence de la protéine Binder of SPerm dans l'interaction spermatozoïde-ovocyte
Informations sur le document
| Langue | French |
| Nombre de pages | 103 |
| Format | |
| Taille | 1.87 MB |
- interaction spermatozoïde-ovocyte
- protéine Binder of SPerm
- fertilisation in vitro
Résumé
I.Main Heading
Sperm-Egg Interaction
The Binder of SPerm (BSP) protein family is implicated in capacitation through biochemical changes in the sperm membrane. In vitro fertilization (IVF) results show that epididymal sperm can be used for fertilization, but fewer epididymal sperm can fertilize oocytes compared to ejaculated sperm. This research study aimed to further functionally characterize the mouse BSPH1 protein through investigating the implication of BSPH1 in sperm-egg interaction.
BSPH1 Localization and Effects on Sperm
BSPH1 Protein was localized to the capacitated sperm head and mid-piece, suggesting a role for this protein beyond its involvement in capacitation. Murine BSPH1 protein has several features similar to bovine seminal vesicles, such as binding to choline phospholipids and inducing cholesterol efflux.
BSPH1 Effects on Oocytes
Pre-incubation of oocytes with recombinant BSPH1 (rec-BSPH1) protein inhibited in vitro fertilization in a dose-dependent manner. Immunofluorescence experiments did not reveal any specific receptors for rec-BSPH1 on the egg surface.
BSA Synergistic Effect
Co-incubation of eggs with BSA and rec-BSPH1 prior to fertilization could induce cholesterol efflux from the egg membrane followed by premature membrane reorganization and compromised sperm-egg interaction. BSPH1 binding to the egg membrane could lead to premature oocyte membrane disorganization.
Sperm Capacitation
Immuno-neutralization of native, sperm-bound BSPH1 using anti-rec-BSPH1 antibodies interrupted downstream signaling triggers for hyperactivation and the acrosome reaction due to obstructed interactions between BSPH1 and cholesterol and players involved in Ca2+ influx over the sperm membrane.
Conclusion
BSPH1 plays a role in sperm-egg interaction and fertilization. Immuno-neutralization of native, sperm-bound BSPH1 affects sperm capacitation and fertilizing ability in vitro.
1. Epididymal milieu and sperm maturation
The epididymis is a long and convoluted post-testicular tubule directing semen into the vas deferens. This duct is constructed of highly specified segments including the initial segment (IS), the caput, the corpus and the cauda epididymidis, with slight species-specific variations. These epididymal segments are further partitioned into sub-segment regions through connective tissue. Segment-specific functions are evidenced by the expression of distinct sets of genes in the different subdivisions [1-3].
2. Structure and function of BSPHs
BSP proteins are mostly acidic and rather small, with molecular weights ranging from 15 to 30 kDa. Depending on the species, between one and six forms of the protein are expressed. They are composed of an N-terminal domain, two fibronectin type II domains (Fn2-A and Fn2-B) and a 7-amino acid linker that is shared among all BSP family members (Figure 3). Some BSPs also have a short, variable C-terminal domain [69]. The Fn2 domains are thought to be responsible for the functional roles of BSP proteins. Two disulfide bonds are found in each domain; thus, each BSP protein contains eight cysteine residues in its primary structure [80].
2.1. Effects of BSPs on sperm in the male and female reproductive tract
Following spermiogenesis, sperm are subjected to maturation events while transiting through the epididymis, where they acquire fertilizing ability and are stored prior to ejaculation. During epididymal transit, maturation events occur; these molecular events allow sperm to acquire motility and lead to considerable modifications to the sperm plasma membrane. These changes render them competent to undergo capacitation and later fertilization events once they reach the female reproductive tract, as well as allow them to remain protected during the rest of their journey to the site of fertilization.
2.2. Effects of BSPs on sperm in a cryopreservation environment
There are also detrimental effects attributable to the long-term exposure of sperm to seminal plasma, and the removal of seminal plasma prior to cryopreservation can enable sperm to tolerate potential cryo-damages [123]. Some data from cryopreservation experiments suggest that the quantity of BSP1 proteins bound to the acrosome of ejaculated sperm is an indicator of the sensitivity of bovine sperm to cryostorage [124].