171:
proteins that make up the zona pellucida, binds to a partner molecule (to the ÎČ1,4-galactosyl transferase receptors) on the sperm. This lock-and-key type mechanism is species-specific and prevents the sperm and egg of different species from fusing. The zona pellucida also releases Ca granules to prevent other sperm from binding. There is some evidence that this binding is what triggers the acrosome to release the enzymes that allow the sperm to fuse with the egg. A similar mechanism likely occurs in other mammals, but the diversity of zona proteins across species means that the relevant protein and receptor may differ.
147:, the site of fertilization, when the sperm penetrates the secondary oocyte. Prior events prepare for the acrosome reaction. The sperm cell undergoes a series of changes, including acquiring a "hyperactive motility pattern" where its flagellum produces vigorous whip-like movements propelling the sperm through the cervical canal and uterine cavity until it reaches the isthmus of the fallopian tube. Various mechanisms, including chemotaxis, aid the sperm in approaching the ovum in the ampulla of the fallopian tube. Once in close proximity, glycoproteins on the outer surface of the sperm bind with glycoproteins on the
20:
51:
39:, a sperm must first fuse with the plasma membrane and then penetrate the female egg cell to fertilize it. While the fusion of the sperm cell with the egg cell's plasma membrane is relatively straightforward, penetrating the egg's protective layers, such as the zona pellucida, presents a significant challenge. Therefore, sperm cells go through a process known as the
116:. Upon coming into contact with the zona pellucida, the acrosomal enzymes begin to dissolve, and the actin filament comes into contact with the zona pellucida. Once the two meet, a calcium influx occurs, causing a signaling cascade. The cortical granules inside the oocyte then fuse to the outer membrane, and a quick fast block reaction occurs.
154:
Sperm that fail to initiate the acrosome reaction prior to reaching to the zona pellucida are unable to penetrate the zona pellucida. Since the acrosome reaction has already occurred, sperm are then able to penetrate the zona pellucida due to mechanical action of the tail, not because of the acrosome
123:
A sperm penetration assay includes an acrosome reaction test that assesses how well a sperm can perform during the fertilization process. Sperm that are unable to go through the acrosome reaction properly will not be able to fertilize an egg. However, this problem only occurs in about 5% of men that
341:
For fluorescence microscopy, a smear of washed sperm cells is made, air-dried, permeabilized, and then stained. Such a slide is then viewed under the light of a wavelength that will cause the probe to fluoresce if it is bound to the acrosomal region. At least 200 cells are considered arbitrarily
46:
The acrosome is a membrane-bound organelle of Golgi apparatus origin, commonly located at the tip of the head of the mature spermatozoon, which contains a variety of enzymes and antigens required for fertilization. It was once called "apical body" because of its location, or "perforatorium" on the
345:
For assessment with flow cytometry, the washed cells are incubated with the chosen probe, possibly passed again, then sampled in a flow cytometer. After gating the cell population according to forward- and side-scatter, the resulting data can be analyzed (E.g. mean fluorescences compared). With
170:
Acrosin, once exposed, digests the zona pellucida and membrane of the oocyte, allowing for penetration to happen. Part of the sperm's cell membrane then fuses with the egg cell's membrane, and the contents of the head sink into the egg. In the mouse, it has been demonstrated that ZP3, one of the
182:
and once bound together, the sperm and the egg fuse together to form two pronuclei. These pronuclei supply the zygote with the genetic material necessary for the formation of an embryo. Additionally, once the fusion of the sperm and oocyte is complete, phospholipase C zeta is released from the
337:
such as FITC-PNA, FITC-PSA, FITC-ConA, or fluoresceinated antibody such as FITC-CD46. The antibodies/lectins have a high specificity for different parts of the acrosomal region, and will only bind to a specific site (acrosomal content/ inner/outer membrane). If bound to a fluorescent molecule,
243:
In mice, it has been well established as physiologically normal and common. Mouse sperm which have undergone fully spontaneous acrosome reaction are still able to fertilize eggs. Furthermore, the rate of spontaneous acrosome reaction is higher in more promiscuous species such as
66:
of the sperm's head, exposing the contents of the acrosome. The contents include surface antigens necessary for binding to the egg's cell membrane, and numerous enzymes which are responsible for breaking through the egg's tough coating and allowing fertilization to occur.
291:
is higher in oocytes injected with spermatozoa that have undergone acrosome reaction (~40%) vs. those injected with nonreacted spermatozoa (~10%). The implantation rate is ~25% in when injected with both reacted and nonreacted spermatozoa. The
84:
In some lower animal species, a protuberance (the acrosomal process) forms at the apex of the sperm head, supported by a core of actin microfilaments. The membrane at the tip of the acrosomal process fuses with the egg's plasma membrane.
119:
Furthermore, the cortical granules inside the oocyte fuse with the outer membrane, initiating a rapid block reaction. This reaction alters a patch of pre-existing sperm plasma membrane, facilitating fusion with the egg plasma membrane.
845:
GĂłmez-Torres, MarĂa JosĂ©; GarcĂa, Eva MarĂa; Guerrero, Jaime; Medina, Sonia; Izquierdo-Rico, MarĂa JosĂ©; Gil-Izquierdo, Ăngel; Orduna, JesĂșs; SavirĂłn, MarĂa; GonzĂĄlez-Brusi, Leopoldo; Ten, Jorge; Bernabeu, Rafael (2015-11-09).
158:
The first stage is the penetration of corona radiata, by releasing hyaluronidase from the acrosome to digest cumulus cells surrounding the oocyte and exposing acrosin attached to the inner membrane of the sperm. The
75:
There are considerable species variations in the morphology and consequences of the acrosome reaction. In several species, the trigger for the acrosome reaction has been identified in a layer that surrounds the egg.
253:
In humans, on the other hand, it remains disputed where exactly the acrosome reaction is initiated in physiological fertilization, due to experimental constraints (for example, animal studies may make use of
342:
and classified as either acrosome intact (fluorescing bright green), or acrosome reacted (no probe present, or only on the equatorial region). It is then expressed as a percentage of the counted cells.
333:
can be used for assessing the shedding of the acrosome or "acrosome reaction" of a sperm sample. Flow cytometry and fluorescence microscopy are usually done after staining with a fluoresceinated
186:
Following penetration and fusion, if all is normally occurring, the process of egg-activation occurs facilitated by proteins like phospholipase C zeta, and the oocyte is said to have become
178:
on the sperm: without the reaction, sperm can still penetrate through the zona pellucida to the egg membrane, but cannot fuse. As seen in mouse studies, IZUMO1 binds to the oocyte protein
190:. This is thought to be induced by a specific protein phospholipase c zeta. It undergoes its secondary meiotic division, and the two haploid nuclei (paternal and maternal) fuse to form a
783:
Bosakova, Tereza; Tockstein, Antonin; Sebkova, Natasa; Simonik, Ondrej; Adamusova, Hana; Albrechtova, Jana; Albrecht, Tomas; Bosakova, Zuzana; Dvorakova-Hortova, Katerina (2018-12-12).
350:(PI) could also be included in order to exclude dead cells from the acrosome assessment, since many sperm cells will spontaneously lose their acrosome when they die.
217:
It is now known that in a certain sense, this phenomenon is physiologically normal across mammalian species. The acrosome reaction is induced by passage through the
202:
zygote, several changes to the egg's cell membranes render them impenetrable shortly after the first sperm enters the egg (such as the rapid loss of JUNO).
167:, and developed in the ovary with the egg and support it as it grows. The acrosome reaction must occur before the sperm cell reaches the zona pellucida.
265:
SAR rate in human sperm to sperm quality and fertilization rate, but the overall results are mixed, and do not seem to be clinically useful as of 2018.
338:
regions where these probes have bound can be visualised. Sperm cells with artificially induced acrosome reactions may serve as positive controls.
1161:
236:
However, the physiological role of truly spontaneous acrosomal reaction, occurring well before this point in the female reproductive tract, or
438:
1196:
956:"Human sperm acrosome function assays are predictive of fertilization rate in vitro: a retrospective cohort study and meta-analysis"
112:; their role in fertilization is not yet clear. The acrosomal reaction is initiated when sperm comes into contact with the oocyte's
1016:
Gianaroli, Luca; Magli, M. Cristina; Ferraretti, Anna P; Crippa, Andor; Lappi, Michela; Capitani, Serena; Baccetti, Baccio (2010).
96:, a significant portion of the exposed acrosomal content contains a protein that temporarily holds the sperm on the egg's surface.
1018:"Birefringence characteristics in sperm heads allow for the selection of reacted spermatozoa for intracytoplasmic sperm injection"
280:
131:, premature acrosome reactions have been found to cause increased motility in aggregates of spermatozoa promoting fertilization.
848:"Metabolites involved in cellular communication among human cumulus-oocyte-complex and sperm during in vitro fertilization"
62:
of the egg, which is necessary for initiating the acrosome reaction, the membrane surrounding the acrosome fuses with the
364:
174:
More recent scientific evidence demonstrates that the acrosomal reaction is necessary to expose a protein called
1153:
299:
The acrosome reaction can be stimulated in vitro by substances a sperm cell may encounter naturally, such as
330:
230:
1100:"Comparative flow cytometric analysis of the human sperm acrosome reaction using CD46 antibody and lectins"
210:
Spermatozoa can initiate the acrosomal reaction well in advance of reaching the zona pellucida, as well as
284:
270:
124:
have the test done. This test is rather expensive and provides limited information on a man's fertility.
226:
1169:
731:
548:
658:"Acrosome-reacted mouse spermatozoa recovered from the perivitelline space can fertilize other eggs"
537:"Acrosome-reacted mouse spermatozoa recovered from the perivitelline space can fertilize other eggs"
246:
43:
reaction, which is the reaction that occurs in the acrosome of the sperm as it approaches the egg.
1191:
656:
Inoue, Naokazu; Satouh, Yuhkoh; Ikawa, Masahito; Okabe, Masaru; Yanagimachi, Ryuzo (2011-12-13).
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in an appropriate culture medium. This is referred to as spontaneous acrosome reaction (SAR).
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Sebkova, Natasa; Ded, Lukas; Vesela, Katerina; Dvorakova-Hortova, Katerina (2014-02-01).
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785:"New Insight into Sperm Capacitation: A Novel Mechanism of 17ÎČ-Estradiol Signalling"
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483:
300:
222:
50:
93:
718:
Bianchi, Enrica; Doe, Brendan; Goulding, David; Wright, Gavin J. (2014-04-24).
662:
Proceedings of the
National Academy of Sciences of the United States of America
468:
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1058:
972:
864:
599:
Ikawa, Masahito; Inoue, Naokazu; Benham, Adam M.; Okabe, Masaru (2010-04-01).
195:
128:
981:
932:
873:
810:
751:
720:"Juno is the egg Izumo receptor and is essential for mammalian fertilisation"
683:
624:
482:
Moore, Harry; DvorĂĄkovĂĄ, Katerina; Jenkins, Nicholas; Breed, William (2002).
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907:"Progress of sperm IZUMO1 relocation during spontaneous acrosome reaction"
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40:
36:
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109:
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assumption that it might assist the spermatozoon boring into the egg.
616:
601:"Fertilization: a sperm's journey to and interaction with the oocyte"
334:
311:
191:
175:
1098:
Carver-Ward, J. A; Moran-Verbeek, I. M; Hollanders, J. M. G (1997).
49:
32:
18:
954:
Xu, Fang; Guo, Ganggang; Zhu, Wenbing; Fan, Liqing (2018-08-24).
1057:
Miyazaki, R; Fukuda, M; Takeuchi, H; Itoh, S; Takada, M (2009).
535:
Inoue, N; Satouh, Y; Ikawa, M; Okabe, M; Yanagimachi, R (2011).
369:
445:. universities of Fribourg, Lausanne and Bern. Archived from
390:"Sperm acrosome reaction: its site and role in fertilization"
163:
are embedded in a gel-like substance made primarily of
388:
Hirohashi, Noritaka; Yanagimachi, Ryuzo (2018-07-01).
221:
cells, mediated by the hormones they secrete (such as
258:
with fluorescent sperm, while human studies cannot).
1059:"Flow Cytometry to Evaluate Acrosome-Reacted Sperm"
261:Studies have been done with the intent of linking
484:"Exceptional sperm cooperation in the wood mouse"
250:, which face a high level of sperm competition.
541:Proceedings of the National Academy of Sciences
139:The acrosomal reaction typically occurs in the
530:
528:
346:this technique, a probe for viability such as
1104:Journal of Assisted Reproduction and Genetics
8:
1011:
1009:
307:, as well as the more commonly used calcium
198:and minimize the possibility of producing a
789:International Journal of Molecular Sciences
469:"Your path to fertility: Acrosome Reaction"
104:In mammals, the acrosome reaction releases
1152:at the U.S. National Library of Medicine
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960:Reproductive Biology and Endocrinology
852:Reproductive Biology and Endocrinology
23:Acrosome reaction on a sea urchin cell
840:
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605:The Journal of Clinical Investigation
7:
713:
711:
594:
592:
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296:per cycle follows the same trend.
14:
1035:10.1016/j.fertnstert.2008.10.024
281:intracytoplasmic sperm injection
127:In other cases, such as in the
88:In some echinoderms, including
1166:Essentials of Human Physiology
129:wood mouse Apodemus sylvaticus
1:
206:Spontaneous acrosome reaction
240:, is a separate phenomenon.
58:As the sperm approaches the
365:Hamster zona-free ovum test
1213:
1197:Animal reproductive system
439:"Chapter 4, Fertilization"
1177:Animation at stanford.edu
1162:"Section 5/5ch8/s5ch8_21"
1076:10.3109/01485019008987613
973:10.1186/s12958-018-0398-y
865:10.1186/s12958-015-0118-9
1154:Medical Subject Headings
71:Variations among species
1022:Fertility and Sterility
675:10.1073/pnas.1116965108
562:10.1073/pnas.1116965108
394:Biology of Reproduction
331:fluorescence microscopy
16:Sperm-meets-egg process
437:Swiss Virtual Campus.
55:
24:
1063:Archives of Andrology
407:10.1093/biolre/ioy045
53:
22:
802:10.3390/ijms19124011
31:to happen between a
924:10.1530/REP-13-0193
744:10.1038/nature13203
736:2014Natur.508..483B
668:(50): 20008â20011.
553:2011PNAS..10820008I
503:10.1038/nature00832
449:on 18 February 2019
247:Apodemus sylvaticus
1116:10.1007/BF02765780
56:
54:Acrosomal Reaction
25:
1160:Nosek, Thomas M.
1150:Acrosome+reaction
730:(7497): 483â487.
360:Cortical reaction
289:implantation rate
155:reaction itself.
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1168:. Archived from
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443:Human Embryology
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348:propidium iodide
305:follicular fluid
219:cumulus oophorus
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64:plasma membrane
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1172:on 2016-03-24.
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1170:the original
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451:. Retrieved
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453:18 February
283:(ICSI) for
279:When using
135:The process
94:sea urchins
80:Echinoderms
1186:Categories
376:References
318:Assessment
196:polyspermy
1192:Andrology
982:1477-7827
966:(1): 81.
933:1741-7899
874:1477-7827
811:1422-0067
752:0028-0836
684:0027-8424
625:0021-9738
416:1529-7268
309:ionophore
188:activated
1044:19064263
1000:30143014
941:24277869
892:26553294
829:30545117
770:24739963
702:22084105
643:20364096
581:22084105
511:12110888
424:29462288
354:See also
272:in vitro
263:in vitro
238:in vitro
212:in vitro
200:triploid
90:starfish
41:acrosome
37:egg cell
1134:9048242
1125:3454831
1085:2285347
991:6109296
883:4640411
858:: 123.
820:6321110
761:3998876
732:Bibcode
693:3250175
634:2846064
572:3250175
549:Bibcode
519:4413444
471:. 2007.
183:sperm.
143:of the
141:ampulla
110:acrosin
100:Mammals
1156:(MeSH)
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724:Nature
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