scholarly journals Membrane Remodeling and Matrix Dispersal Intermediates During Mammalian Acrosomal Exocytosis

2021 ◽  
Vol 9 ◽  
Author(s):  
Miguel Ricardo Leung ◽  
Ravi Teja Ravi ◽  
Bart M. Gadella ◽  
Tzviya Zeev-Ben-Mordehai
Keyword(s):  
Plasma Membrane ◽  
Reproductive Tract ◽  
Morphological Changes ◽  
Female Reproductive Tract ◽  
Cell Integrity ◽  
Membrane Fission ◽  
Mammalian Sperm ◽  
Acrosomal Exocytosis ◽  
Plausible Mechanism ◽  
Structural Mechanisms

To become fertilization-competent, mammalian sperm must undergo a complex series of biochemical and morphological changes in the female reproductive tract. These changes, collectively called capacitation, culminate in the exocytosis of the acrosome, a large vesicle overlying the nucleus. Acrosomal exocytosis is not an all-or-nothing event but rather a regulated process in which vesicle cargo disperses gradually. However, the structural mechanisms underlying this controlled release remain undefined. In addition, unlike other exocytotic events, fusing membranes are shed as vesicles; the cell thus loses the entire anterior two-thirds of its plasma membrane and yet remains intact, while the remaining nonvesiculated plasma membrane becomes fusogenic. Precisely how cell integrity is maintained throughout this drastic vesiculation process is unclear, as is how it ultimately leads to the acquisition of fusion competence. Here, we use cryoelectron tomography to visualize these processes in unfixed, unstained, fully hydrated sperm. We show that paracrystalline structures within the acrosome disassemble during capacitation and acrosomal exocytosis, representing a plausible mechanism for gradual dispersal of the acrosomal matrix. We find that the architecture of the sperm head supports an atypical membrane fission–fusion pathway that maintains cell integrity. Finally, we detail how the acrosome reaction transforms both the micron-scale topography and the nanoscale protein landscape of the sperm surface, thus priming the sperm for fertilization.

scholarly journals Membrane remodeling and matrix dispersal intermediates during mammalian acrosomal exocytosis

2021 ◽  
Author(s):  
Miguel Ricardo Leung ◽  
Ravi Teja Ravi ◽  
Bart Gadella ◽  
Tzviya Zeev-Ben-Mordehai
Keyword(s):  
Plasma Membrane ◽  
Reproductive Tract ◽  
Electron Tomography ◽  
Morphological Changes ◽  
Female Reproductive Tract ◽  
Cell Integrity ◽  
Membrane Fission ◽  
Mammalian Sperm ◽  
Acrosomal Exocytosis ◽  
Structural Mechanisms

To become fertilization-competent, mammalian sperm must undergo a complex series of biochemical and morphological changes in the female reproductive tract. These changes, collectively called capacitation, culminate in the exocytosis of the acrosome, a large vesicle overlying the nucleus. Acrosomal exocytosis is not an all-or-nothing event, but rather a regulated process in which vesicle cargo disperses gradually. However, the structural mechanisms underlying this controlled release remain undefined. In addition, unlike other exocytotic events, fusing membranes are shed as vesicles; the cell thus loses the entire anterior two-thirds of its plasma membrane and yet remains intact while the remaining non-vesiculated plasma membrane becomes fusogenic. Precisely how cell integrity is maintained throughout this drastic vesiculation process is unclear, as is how it ultimately leads to the acquisition of fusion competence. Here, we use cryo-electron tomography to visualize these processes in unfixed, unstained, fully-hydrated sperm. We show that crystalline structures within the acrosome disassemble during capacitation and acrosomal exocytosis, representing a plausible mechanism for gradual dispersal of the acrosomal matrix. We find that the architecture of the sperm head supports an atypical membrane fission-fusion pathway that maintains cell integrity. Finally, we detail how the acrosome reaction transforms both the micron-scale topography and the nano-scale protein landscape of the sperm surface, thus priming the sperm for fertilization.

scholarly journals Role of actin cytoskeleton in mammalian sperm capacitation and the acrosome reaction

Reproduction ◽  
2005 ◽  
Vol 129 (3) ◽  
pp. 263-268 ◽  
Author(s):  
Haim Breitbart ◽  
Gili Cohen ◽  
Sara Rubinstein
Keyword(s):  
Plasma Membrane ◽  
Zona Pellucida ◽  
Acrosome Reaction ◽  
Reproductive Tract ◽  
Female Reproductive Tract ◽  
Mammalian Sperm ◽  
Acrosomal Membrane ◽  
Close Proximity ◽  
Sperm Plasma Membrane ◽  
To Come

In order to fertilize, the mammalian spermatozoa should reside in the female reproductive tract for several hours, during which they undergo a series of biochemical modifications collectively called capacitation. Only capacitated sperm can undergo the acrosome reaction after binding to the egg zona pellucida, a process which enables sperm to penetrate into the egg and fertilize it. Polymerization of globular (G)-actin to filamentous (F)-actin occurs during capacitation, depending on protein kinase A activation, protein tyrosine phosphorylation, and phospholipase D activation. F-actin formation is important for the translocation of phospholipase C from the cytosol to the sperm plasma membrane during capacitation. Prior to the occurrence of the acrosome reaction, the F-actin should undergo depolymerization, a necessary process which enables the outer acrosomal membrane and the overlying plasma membrane to come into close proximity and fuse. The binding of the capacitated sperm to the zona pellucida induces a fast increase in sperm intracellular calcium, activation of actin severing proteins which break down the actin fibers, and allows the acrosome reaction to take place.

scholarly journals Integration of Sperm Motility and Chemotaxis Screening with a Microchannel-Based Device

2010 ◽  
Vol 56 (8) ◽  
pp. 1270-1278 ◽  
Author(s):  
Lan Xie ◽  
Rui Ma ◽  
Chao Han ◽  
Kai Su ◽  
Qiufang Zhang ◽  
...  
Keyword(s):  
Sperm Motility ◽  
Reproductive Tract ◽  
Cumulus Cells ◽  
Female Reproductive Tract ◽  
Straight Channel ◽  
Vitro Fertilization ◽  
Mammalian Sperm ◽  
Reaction Capability ◽  
Mammalian Female

BACKGROUND Sperm screening is an essential step in in vitro fertilization (IVF) procedures. The swim-up method, an assay for sperm motility, is used clinically to select the ideal sperm for subsequent manipulation. However, additional parameters, including acrosome reaction capability, chemotaxis, and thermotaxis, are also important indicators of mammalian sperm health. To monitor both sperm motility and chemotaxis simultaneously during sperm screening, we designed and constructed a microdevice comprising a straight channel connected with a bibranch channel that mimics the mammalian female reproductive tract. METHODS The width and length of the straight channel were optimized to select the motile sperms. We selectively cultured cumulus cells in the bibranch channel to generate a chemoattractant-forming chemical gradient. Sperm chemotaxis was represented by the ratio of the sperm swimming toward different branches. RESULTS The percentage of motile sperms improved from 58.5% (3.8%) to 82.6% (2.9%) by a straight channel 7 mm in length and 1 mm in width. About 10% of sperms were found to be chemotactically responsive in our experiment, which is consistent with previous studies. CONCLUSIONS For the first time, we achieved the combined evaluation of both sperm motility and chemotaxis. The motile and chemotactically responsive sperms can easily be enriched on a lab-on-a-chip device to improve IVF outcome.

scholarly journals Inhibition of mouse fertilization in vivo by intra-oviductal injection of an anti-equatorin monoclonal antibody

Reproduction ◽  
2001 ◽  
pp. 649-655 ◽  
Author(s):  
K Yoshinaga ◽  
DK Saxena ◽  
T Oh-oka ◽  
I Tanii ◽  
K Toshimori
Keyword(s):  
Monoclonal Antibody ◽  
Reproductive Tract ◽  
Female Reproductive Tract ◽  
Pathological Changes ◽  
Histological Studies ◽  
Control Side ◽  
Mammalian Sperm ◽  
The Right ◽  
And Control

The monoclonal antibody mMN9 recognizes an antigenic molecule, equatorin, which is localized at the equatorial segment of the mammalian sperm acrosome. Our previous results using an IVF system indicated that mMN9 blocked sperm-oocyte fusion. Antibody-containing and control solutions were injected directly into the right and left oviductal ampullae, respectively, of anaesthetized female mice to assess the effect of mMN9 on fertilization in vivo. After hCG treatment, the females were mated, and their oviductal eggs and implanted embryos were examined. mMN9 was retained in the oviductal lumen at 20 h after injection. The rates of fertilization and concomitant pregnancy were significantly lower than in the control side (P < 0.05). In addition, histological studies showed no evidence of pathological changes in the female reproductive tract after the injections. These results indicate that mMN9 inhibits mouse fertilization significantly under in vivo conditions and that this injection method should be useful for studying the effects of antibodies and agents on fertilization in vivo.

scholarly journals Role of spermine in mammalian sperm capacitation and acrosome reaction

1991 ◽  
Vol 278 (1) ◽  
pp. 25-28 ◽  
Author(s):  
S Rubinstein ◽  
H Breitbart
Keyword(s):  
Binding Sites ◽  
Acrosome Reaction ◽  
Reproductive Tract ◽  
Female Reproductive Tract ◽  
Sperm Capacitation ◽  
Amino Groups ◽  
Binding Properties ◽  
Mammalian Sperm ◽  
Energy Dependent

The binding properties of seminal polyamines to ram spermatozoa and their possible role in sperm capacitation and the acrosome reaction were studied. Binding and release of [14C]spermine from ram spermatozoa occurred at a rate faster than in somatic cells and were not energy-dependent. Release of bound spermine was further facilitated by heparin, a constituent of the female reproductive tract which was reported to induce capacitation and the acrosome reaction. High- and low-affinity polyamine-binding sites were identified, of which the high-affinity site was specific to polyamines with three or more amino groups. We also found that spermine inhibited the acrosome reaction and propose that it is the major seminal decapacitating factor. Since precise timing of capacitation and the acrosome reaction are critical for successful fertilization, it is suggested that the role of seminal spermine is to prevent premature capacitation and the acrosome reaction.

scholarly journals Effect of flagellar beating pattern on sperm rheotaxis and boundary-dependent navigation

2020 ◽  
Author(s):  
Meisam Zaferani ◽  
Farhad Javi ◽  
Amir Mokhtare ◽  
Alireza Abbaspourrad
Keyword(s):  
Reproductive Tract ◽  
Complex Structure ◽  
Clinical Importance ◽  
Microfluidic System ◽  
Female Reproductive Tract ◽  
Circular Motion ◽  
Sperm Cells ◽  
Progressive Motility ◽  
Mammalian Sperm ◽  
Correct Path

AbstractThe study of navigational mechanisms used by mammalian sperm inside a microenvironment yields better understanding of sperm locomotion during the insemination process, which aids in the design of tools for overcoming infertility. Near- and far-field hydrodynamic interactions with nearby boundaries and rheotaxis are known to be some of the steering strategies that keep sperm on the correct path toward the egg. However, it is not known how the beating patterns of sperm may influence these navigational strategies. In this study, we investigate the effect of flagellar beating pattern on navigation of sperm cells both theoretically and experimentally using a two-step approach. We first isolate bovine sperm based on their rheotactic behavior in a zone with quiescent medium using a microfluidic system. This step ensures that the swimmers are able to navigate upstream and have motilities higher than a selected value, even though they feature various flagellar beating patterns. We then explore the flagellar beating pattern of these isolated sperm and their subsequent influence on boundary-dependent navigation. Our findings indicate that rheotaxis enables sperm to navigate upstream even in the presence of circular motion in their motility, whereas boundary-dependent navigation is more sensitive to the circular motion and selects for progressive motility. This finding may explain the clinical importance of progressive motility in semen samples for fertility, as the flow of mucus may not be sufficiently strong to orient the sperm cells throughout the process of insemination.SignificanceFinding the egg and moving toward it while traversing the complex structure of the female reproductive tract is necessary for mammalian sperm. Previous studies have shown how sperm use navigational steering mechanisms that are based on swimming upstream (i.e. rheotaxis) and along the boundaries of the female reproductive tract. We demonstrate that the performance of theses navigational mechanisms is associated with the primary characteristics of sperm motility. In fact, sperm rheotaxis is more sensitive to the motility and thus average velocity of sperm while navigation via rigid boundaries is more sensitive to the flagellar beating pattern and selects for symmetric beating. Our results can be expanded to other autonomous microswimmers and their subsequent navigation mechanisms.

scholarly journals Activation of sperm in the female reproductive tract in mammals

2020 ◽  
Vol 76 (09) ◽  
pp. 6445-2020
Author(s):  
ALEKSANDRA KRAWCZYK ◽  
JADWIGA JAWORSKA-ADAMU
Keyword(s):  
Plasma Membrane ◽  
Acrosome Reaction ◽  
Reproductive Tract ◽  
Female Reproductive Tract ◽  
Perivitelline Space ◽  
Male Gametes ◽  
Activation Mechanisms ◽  
Sperm Plasma Membrane ◽  
Controlled Reproduction ◽  
Two Stages

The formation of a new diploidal organism is preceded by a series of mutual interactions of haploidal gametes. This process is very complicated and requires the prior activation of reproductive cells. Male gametes eventually mature in the female reproductive tract, acquiring mobility and fertilization. This process takes place in two stages. Sperms are first capacitated. This phenomenon is reversible and leads to structural, cytophysiological and biochemical changes in the sperm plasma membrane as well as to the sperm hyperactivation. Then, due to the contact with the zona pellucida of the oocyte, the irreversible acrosome reaction occurs. This process involves the fusion of the sperm plasma membrane with the outer membrane of the acrosome, the release of enzymes and exposure of the inner acrosome membrane. This enables sperm to penetrate towards the perivitelline space and oolemma. Contact with the oocyte initiates a series of interactions leading to egg activation and the fusion of gametes. Each of these stages involves many different factors that result in the recognition, attraction and adhesion of reproductive cells. Knowledge about the activation mechanisms can improve the effectiveness of supported and controlled reproduction techniques.

scholarly journals Structure and Function of Caltrin (Calcium Transport Inhibitor) Proteins

2017 ◽  
Vol 10 ◽  
pp. 117862641774582
Author(s):  
Ernesto Javier Grasso ◽  
Carlos Enrique Coronel
Keyword(s):  
Intracellular Signaling ◽  
Calcium Transport ◽  
Molecular Mechanisms ◽  
Reproductive Tract ◽  
Structural Features ◽  
Female Reproductive Tract ◽  
Sperm Cells ◽  
Transport Inhibitor ◽  
Acrosomal Exocytosis ◽  
And Function

Caltrin (calcium transport inhibitor) is a family of small and basic proteins of the mammalian seminal plasma which bind to sperm cells during ejaculation and inhibit the extracellular Ca2+ uptake, preventing the premature acrosomal exocytosis and hyperactivation when sperm cells ascend through the female reproductive tract. The binding of caltrin proteins to specific areas of the sperm surface suggests the existence of caltrin receptors, or precise protein-phospholipid arrangements in the sperm membrane, distributed in the regions where Ca2+ influx may take place. However, the molecular mechanisms of recognition and interaction between caltrin and spermatozoa have not been elucidated. Therefore, the aim of this article is to describe in depth the known structural features and functional properties of caltrin proteins, to find out how they may possibly interact with the sperm membranes to control the intracellular signaling that trigger physiological events required for fertilization.

Effects of ovarian steroids and pregnancy on adrenergic nerves of uterus and oviduct

1981 ◽  
Vol 240 (5) ◽  
pp. C165-C174 ◽  
Author(s):  
J. M. Marshall
Keyword(s):  
Reproductive Tract ◽  
Morphological Changes ◽  
Model System ◽  
Female Reproductive Tract ◽  
Neuroendocrine Regulation ◽  
Nerve Terminals ◽  
Ovarian Steroids ◽  
Adrenergic Neurons ◽  
Per Se ◽  
Muscle Cell Membrane

This review concerns the influence of ovarian steroids and of pregnancy on norepinephrine (NE) metabolism in the adrenergic neurons of the female reproductive tract and speculates on the physiological consequences of this influence. Estrogen and progesterone affect not only the NE content of these nerves but also the turnover of NE, the activity of its synthetic enzyme, and releases of NE from nerve terminals. During pregnancy additional factors including stretch-induced hypertrophy come into play and cause degeneration of the nerves in the uterine corpus. This degeneration makes the muscle supersensitive to NE and may also induce morphological changes in the muscle cell membrane. As a result there may be a withdrawal of neural inhibitory influences on the corpus, allowing spontaneous myogenic contractions to intensify. Although the physiological significance of the steroid-transmitter interactions are still unclear, these nerves per se are of interest because they represent a model system for the study of neuroendocrine regulation in the peripheral nervous system.

50 BOVINE SPERM DEATH KINETICS: TEMPORAL CHANGES IN PRODUCTION OF REACTIVE OXYGEN SPECIES AND PLASMA MEMBRANE INJURY OF DAIRY AND BEEF FROZEN–THAWED SEMEN

2015 ◽  
Vol 27 (1) ◽  
pp. 118
Author(s):  
M. Ahmad ◽  
N. Ahmad ◽  
M. Anzar
Keyword(s):  
Reactive Oxygen Species ◽  
Hydrogen Peroxide ◽  
Plasma Membrane ◽  
Reproductive Tract ◽  
Superoxide Radical ◽  
Reactive Oxygen ◽  
Female Reproductive Tract ◽  
Oxygen Species ◽  
Live Sperm ◽  
Over Time

The extent of changes in sperm structure and function affect the success of fertilization ultimately during the pathway to ovum in the female reproductive tract. The success of AI with frozen-thawed semen varies in dairy and beef breeds of bovine because of differed alterations in sperm during transport in female tract after insemination. To our knowledge, no report is available comparing the changes in dairy and beef sperm leading to death in female tract. Therefore, this study was aimed to investigate the changes in motility, generation of reactive oxygen species (superoxide and hydrogen peroxide), and their relation to sperm death [asymmetry (apoptosis) and rupture of plasma membrane] of dairy and beef frozen-thawed semen during incubation at 37°C for 24 h. This incubation was aimed to mimic the environment of female reproductive tract. Frozen dairy semen (n = 4 bulls) was procured from a Canadian breeding station, whereas beef semen was collected from breeding beef bulls (n = 3; 5 replicates), diluted with Tris-based extender (composition was same as used in dairy semen), cooled to +4°C over 90 min, and cryopreserved by programmable freezer using standard rate as used in dairy semen. Two straws per replicate were thawed at 37°C from both types of semen, pooled separately, and incubated at 37°C for 24 h in capped tubes. Each pooled semen sample was evaluated for motility with CASA, superoxide (O2–, and hydrogen peroxide (H2O2) radical using HE/YoPRO and H2DCFDA/PI assay, respectively, and asymmetry of plasma membrane using YoPRO/PI assay through flow cytometric analysis at 0, 2, 4, 6, 12, and 24 h of incubation. The MIXED procedure of SAS (SAS Institute Inc., Cary, NC, USA) was used to analyse the data as 2 × 6 factorial model for 2 types of semen (dairy and beef) and 6 time points using time as repeated measure. A threshold limit of 30% was considered for motility and live sperm to get optimum fertility. Sperm motility remained higher (P < 0.05) than threshold limit till 6 h in dairy (50.95 ± 2.62%) and 2 h in beef semen (30.28 ± 6.95%). Dairy semen possessed more (P < 0.05) nonapoptotic sperm without O2– (HE–/YoPRO–) till 6 h of incubation than beef semen. The increase in apoptotic sperm containing superoxide radical (HE+/YoPRO+) over time was more (P < 0.05) in beef semen till 6 h of incubation. The rise in dead sperm containing H2O2 (H2DCFDA+/PI+) was recorded more in beef than in dairy semen until 6 h of incubation. Live sperm without apoptosis (YoPRO–/PI–) were higher until 24 h in dairy (49.36 ± 4.56%) compared with beef semen (24.89 ± 3.85%), whereas viable sperm with apoptosis (YoPRO+/PI–) were found similar in both types of semen over time. In conclusion, dairy frozen-thawed semen possessed more live sperm without reactive oxygen species (superoxide and hydrogen peroxide) until 6 h of incubation than did beef semen. The decrease in superoxide radical was more in dairy than in beef semen. Dead and apoptotic sperm increased more in beef frozen-thawed semen over time during incubation. This inference suggests performing the insemination late near ovulation with beef frozen-thawed semen because of less viable life than dairy semen.

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