Zona pellucida

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The zona pellucida (Latin meaning "transparent zone") is the specialized area surrounding mammalian oocytes (eggs). It is also known as an egg coat. The zona pellucida is essential for oocyte growth and fertilization.

Contents

Zona pellucida
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Human ovum: The zona pellucida is seen as a thick clear girdle surrounded by the cells of the corona radiata.
Identifiers
MeSH D015044
FMA 18674
Anatomical terminology

The zona pellucida is an extracellular matrix that surrounds the plasma membrane of the egg cell. It helps protect the egg, and has an essential role in fertilization by sperm. It is surrounded by the corona radiata. The corona is composed of cells that care for the egg when it is emitted from the ovary. [1]

Structure

The zona pellucida is a translucent matrix of cross-linked glycoprotein filaments that surrounds the mammalian oocyte and is 6.5–20 μm thick depending on the species. Its formation, which depends on a conserved zona pellucida-like (ZP) module that mediates the polymerization of egg coat components, [2] is critical to successful fertilization. [3] In non-mammals, it is called the vitelline membrane or vitelline envelope. [4]

Function

The thick membrane of the zona pellucida functions to only allow species-specific fertilization; to prevent polyspermy, and enable the acrosome reaction for the successful adhesion and penetration by the sperm cell. It also allows correct embryo development and size. The major glycoproteins of the egg coat responsible, are known as sperm-binding proteins. [5]

The zona pellucida binds spermatozoa, and is required to initiate the acrosome reaction. In mice, the zona glycoprotein (ZP3) is responsible for sperm binding, adhering to proteins on the sperm plasma membrane. During the acrosome reaction, a sperm cell releases the DNA contained in the acrosomal vesicle into the egg. In other species, the process is slightly different and more complicated. Several more zona proteins have been identified. [6] [7]

The four major sperm-binding proteins, or sperm-receptors, are ZP1, ZP2, ZP3, and ZP4. They bind to capacitated spermatozoa and induce the acrosome reaction. Successful fertilization depends on the ability of sperm to penetrate the extracellular matrix of the zona pellucida that surrounds the egg.[ citation needed ] In the mouse:

In humans, five days after fertilization, the blastocyst performs zona hatching; the zona pellucida degenerates and decomposes, to be replaced by the underlying layer of trophoblastic cells.[ citation needed ]

Immunocontraception

ZP module-containing glycoproteins ZP1, ZP2, ZP3 and ZP4 are targets for immunocontraception in mammals.[ citation needed ]

In non-mammals, the zona pellucida is called the vitelline membrane or envelope, and the vitelline envelope in insects, and plays an important role in preventing cross-breeding of different species, especially in species such as fish that fertilize outside of the body.[ citation needed ]

The zona pellucida is commonly used to control wildlife population problems by immunocontraception. When the zona pellucida of one animal species is injected into the bloodstream of another, it results in sterility of the second species due to immune response. This effect can be temporary or permanent, depending on the method used. In New Jersey, immunocontraception using porcine zona pellucida has been trialled for the control of deer. [8]

Additional images

Related Research Articles

<span class="mw-page-title-main">Spermatozoon</span> Motile sperm cell

A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote.

<span class="mw-page-title-main">Fertilisation</span> Union of gametes of opposite sexes during the process of sexual reproduction to form a zygote

Fertilisation or fertilization, also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a zygote and initiate its development into a new individual organism or offspring. While processes such as insemination or pollination, which happen before the fusion of gametes, are also sometimes informally referred to as fertilisation, these are technically separate processes. The cycle of fertilisation and development of new individuals is called sexual reproduction. During double fertilisation in angiosperms, the haploid male gamete combines with two haploid polar nuclei to form a triploid primary endosperm nucleus by the process of vegetative fertilisation.

<span class="mw-page-title-main">Acrosome reaction</span> Sperm-meets-egg process

For fertilization to happen between a sperm and egg cell, 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 acrosome reaction, which is the reaction that occurs in the acrosome of the sperm as it approaches the egg.

Capacitation is the penultimate step in the maturation of mammalian spermatozoa and is required to render them competent to fertilize an oocyte. This step is a biochemical event; the sperm move normally and look mature prior to capacitation. In vivo, capacitation occurs after ejaculation, when the spermatozoa leave the vagina and enter the upper female reproductive tract. The uterus aids in the steps of capacitation by secreting sterol-binding albumin, lipoproteins, and proteolytic and glycosidasic enzymes such as heparin.

Hyperactivation is a type of sperm motility. Hyperactivated sperm motility is characterised by a high amplitude, asymmetrical beating pattern of the sperm tail (flagellum). This type of motility may aid in sperm penetration of the zona pellucida, which encloses the ovum.

<span class="mw-page-title-main">Acrosin</span> Mammalian protein found in Homo sapiens

Acrosin is a digestive enzyme that acts as a protease. In humans, acrosin is encoded by the ACR gene. Acrosin is released from the acrosome of spermatozoa as a consequence of the acrosome reaction. It aids in the penetration of the Zona Pellucida.

<span class="mw-page-title-main">Human fertilization</span> Union of a human egg and sperm

Human fertilization is the union of an egg and sperm, occurring primarily in the ampulla of the fallopian tube. The result of this union leads to the production of a fertilized egg called a zygote, initiating embryonic development. Scientists discovered the dynamics of human fertilization in the 19th century.

<span class="mw-page-title-main">Cortical reaction</span> Biological process that prevents polyspermy

The cortical reaction is a process initiated during fertilization that prevents polyspermy, the fusion of multiple sperm with one egg. In contrast to the fast block of polyspermy which immediately but temporarily blocks additional sperm from fertilizing the egg, the cortical reaction gradually establishes a permanent barrier to sperm entry and functions as the main part of the slow block of polyspermy in many animals.

The vitelline membrane or vitelline envelope is a structure surrounding the outer surface of the plasma membrane of an ovum or, in some animals, the extracellular yolk and the oolemma. It is composed mostly of protein fibers, with protein receptors needed for sperm binding which, in turn, are bound to sperm plasma membrane receptors. The species-specificity between these receptors contributes to prevention of breeding between different species. It is called zona pellucida in mammals. Between the vitelline membrane and zona pellucida is a fluid-filled perivitelline space.

Sialyl-Lewis <sup>X</sup> Chemical compound

Sialyl LewisX (sLeX), also known as cluster of differentiation 15s (CD15s) or stage-specific embryonic antigen 1 (SSEA-1), is a tetrasaccharide carbohydrate which is usually attached to O-glycans on the surface of cells. It is known to play a vital role in cell-to-cell recognition processes. It is also the means by which an egg attracts sperm; first, to stick to it, then bond with it and eventually form a zygote.

<span class="mw-page-title-main">ZP3</span> Protein-coding gene in the species Homo sapiens

Zona pellucida sperm-binding protein 3, also known as zona pellucida glycoprotein 3 (Zp-3) or the sperm receptor, is a ZP module-containing protein that in humans is encoded by the ZP3 gene. ZP3 is the glycoprotein in the zona pellucida most important for inducting the acrosome reaction of sperm cells at the beginning of fertilization.

Immunocontraception is the use of an animal's immune system to prevent it from fertilizing offspring. Contraceptives of this type are not currently approved for human use.

<span class="mw-page-title-main">ZP2</span> Protein-coding gene in the species Homo sapiens

Zona pellucida sperm-binding protein 2 is a protein that in humans is encoded by the ZP2 gene.

<span class="mw-page-title-main">ZP4</span> Protein-coding gene in the species Homo sapiens

Zona pellucida sperm-binding protein 4, ZP-4 or avilesine, named after its discoverer Manuel Avilés Sánchez is a protein that in humans is encoded by the ZP4 gene.

Vitellin is a protein found in the egg yolk. It is a phosphoprotein. Vitellin is a generic name for major of many yolk proteins.

The zona pellucida-like domain is a large protein region of about 260 amino acids. It has been recognised in a variety of receptor-like eukaryotic glycoproteins. All of these molecules are mosaic proteins with a large extracellular region composed of various domains, often followed by either a transmembrane region and a very short cytoplasmic region or by a GPI-anchor.

Oocyteactivation is a series of processes that occur in the oocyte during fertilization.

<span class="mw-page-title-main">Cortical granule</span>

Cortical granules are regulatory secretory organelles found within oocytes and are most associated with polyspermy prevention after the event of fertilization. Cortical granules are found among all mammals, many vertebrates, and some invertebrates. Within the oocyte, cortical granules are located along the cortex, the region furthest from the cell's center. Following fertilization, a signaling pathway induces the cortical granules to fuse with the oocyte's cell membrane and release their contents into the oocyte's extracellular matrix. This exocytosis of cortical granules is known as the cortical reaction. In mammals, the oocyte's extracellular matrix includes a surrounding layer of perivitelline space, zona pellucida, and finally cumulus cells. Experimental evidence has demonstrated that the released contents of the cortical granules modify the oocyte's extracellular matrix, particularly the zona pellucida. This alteration of the zona pellucida components is known as the zona reaction. The cortical reaction does not occur in all mammals, suggesting the likelihood of other functional purposes for cortical granules. In addition to modifying the oocyte's extracellular matrix and establishing a block to polyspermy, the exocytosis of cortical granules may also contribute towards protection and support of the developing embryo during preimplantation. Once the cortical granules complete their functions, the oocyte does not replenish them.

Zona pellucida sperm-binding protein 1 is a protein that cross-links ZP2 and ZP3. Aberrant ZP1 results in sequestration of ZP3 in the cytoplasm, thereby preventing the formation of the zona pellucida around the oocyte.

Paul Michael Wassarman is an American biologist who has been Professor in the Dept. of Cell, Developmental, and Regenerative Biology at the Icahn School of Medicine at Mount Sinai since 1996. His laboratory identified and characterised proteins that make up the zona pellucida (ZP) of mammalian eggs and determined their role in fertilisation.

References

  1. Gilbert, Scott (2013). Developmental Biology. Sinauer Associates Inc. p. 123. ISBN   9781605351926.
  2. Jovine L, Qi H, Williams Z, Litscher E, de Sanctis D, Wassarman PM (2002). "The ZP domain is a conserved module for polymerization of extracellular proteins". Nat. Cell Biol. 4 (6): 457–461. doi:10.1038/ncb802. PMID   12021773. S2CID   11575790.
  3. Gupta, SK; et al. (September 2012). "Mammalian zona pellucida glycoproteins: structure and function during fertilization". Cell and Tissue Research. 349 (3): 665–78. doi:10.1007/s00441-011-1319-y. PMID   22298023. S2CID   16174953.
  4. Monné, M; Jovine, L (October 2011). "A structural view of egg coat architecture and function in fertilization". Biology of Reproduction. 85 (4): 661–9. doi: 10.1095/biolreprod.111.092098 . hdl: 11563/21648 . PMID   21715714.
  5. Gupta, SK; Bansal, P; Ganguly, A; Bhandari, B; Chakrabarti, K (December 2009). "Human zona pellucida glycoproteins: functional relevance during fertilization". Journal of Reproductive Immunology. 83 (1–2): 50–5. doi: 10.1016/j.jri.2009.07.008 . PMID   19850354.
  6. Conner, SJ; Hughes, DC (2003). "Analysis of fish ZP1/ZPB homologous genes--evidence for both genome duplication and species-specific amplification models of evolution". Reproduction. 126 (3): 347–52. doi: 10.1530/rep.0.1260347 . PMID   12968942.
  7. Conner, S.J.; Lefièvre, L; Hughes, DC; Barratt, CL (2005). "Cracking the egg: Increased complexity in the zona pellucida". Human Reproduction. 20 (5): 1148–52. doi: 10.1093/humrep/deh835 . PMID   15760956.
  8. "Community-Based Deer Management". New Jersey Department of Environmental Protection. 24 September 2014. Retrieved 8 July 2015.

Further reading