Zona pellucida
Encyclopedia
The zona pellucida is a glycoprotein
membrane surrounding the plasma membrane of an oocyte
. It is a vital constitutive part of the latter, external but of essential importance to it. The zona pellucida first appears in multilaminar primary oocytes.
This structure binds spermatozoa, and is required to initiate the acrosome reaction
.
In the mouse (the best characterised mammalian system) the zona glycoprotein, ZP3
, is responsible for sperm binding, adhering to protein
s on the sperm plasma membrane (GalT). ZP3 is then involved in the induction of the acrosome reaction, whereby a spermatozoon releases the contents of the acrosomal vesicle
. The exact characterisation of what occurs in other species has become more complicated as further zona proteins have been identified.
In humans, five days after the fertilization, the blastocyst
performs zona hatching
; the zona pellucida degenerates and decomposes to be replaced by the underlying layer of trophoblast
ic cells.
The zona pellucida is essential for oocyte
death and fertilization.
In some older texts, it has also been called zona striata and stratum lucidum (not to be confused with the stratum lucidum
of the skin).
in the human.
In non-mammalian animals, the zona pellucida (called vitelline layer) plays an important role in preventing cross-breeding of different species, especially in species that fertilize outside of the body (e.g. fish
).
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
, Porcine zona pellucida
is used to keep deer
populations low, and this process is commonly referred to as "spay-vac".
and ZP4
bind to capacitated spermatozoa and induce the acrosome reaction
.Successful fertilization depends on the ability of sperm to penetrate extracellular matrix surrounding eggs.
In the mouse:
Data with native human protein is not currently available.
Glycoprotein
Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...
membrane surrounding the plasma membrane of an oocyte
Oocyte
An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell which undergoes a mitotic...
. It is a vital constitutive part of the latter, external but of essential importance to it. The zona pellucida first appears in multilaminar primary oocytes.
This structure binds spermatozoa, and is required to initiate the acrosome reaction
Acrosome reaction
During fertilization, a sperm must first fuse with the plasma membrane and then penetrate the female egg in order to fertilize it. Fusing to the egg usually causes little problem, whereas penetrating through the egg's hard shell can present more of a problem to the sperm...
.
In the mouse (the best characterised mammalian system) the zona glycoprotein, ZP3
ZP3
Zona pellucida sperm-binding protein 3, also known as zona pellucida glycoprotein 3 or the sperm receptor, is a protein that in humans is encoded by the ZP3 gene...
, is responsible for sperm binding, adhering to protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s on the sperm plasma membrane (GalT). ZP3 is then involved in the induction of the acrosome reaction, whereby a spermatozoon releases the contents of the acrosomal vesicle
Acrosome
The acrosome is an organelle that develops over the anterior half of the head in the spermatozoa of many animals. It is a cap-like structure derived from the Golgi apparatus. Acrosome formation is completed during testicular maturation. In Eutherian mammals the acrosome contains digestive enzymes...
. The exact characterisation of what occurs in other species has become more complicated as further zona proteins have been identified.
In humans, five days after the fertilization, the blastocyst
Blastocyst
The blastocyst is a structure formed in the early embryogenesis of mammals, after the formation of the morula. It is a specifically mammalian example of a blastula. It possesses an inner cell mass , or embryoblast, which subsequently forms the embryo, and an outer layer of cells, or trophoblast,...
performs zona hatching
Zona hatching
Zona hatching is a phenomenon occurring during prenatal development. Prior to this event, the predecessor of the embryo, in the form of a blastocyst, is surrounded by a glycoprotein sphere called the zona pellucida. To be able to perform implantation on the uterine wall, the blastocyst first needs...
; the zona pellucida degenerates and decomposes to be replaced by the underlying layer of trophoblast
Trophoblast
Trophoblasts are cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta. They are formed during the first stage of pregnancy and are the first cells to differentiate from the fertilized egg...
ic cells.
The zona pellucida is essential for oocyte
Oocyte
An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell which undergoes a mitotic...
death and fertilization.
In some older texts, it has also been called zona striata and stratum lucidum (not to be confused with the stratum lucidum
Stratum lucidum
The stratum lucidum is a thin, clear layer of dead skin cells in the epidermis named for its translucent appearance under a microscope...
of the skin).
Immunocontraception
Glycoproteins in ZP1, 2, 3 and 4 are targets for immunocontraceptionImmunocontraception
Immunocontraception is a birth control method that uses the body's immune response to prevent pregnancy.-In humans:Experiments are undergoing to test the effectiveness of an immunocontraceptive vaccine that inhibits the fusing of spermatozoa to the zona pellucida. This vaccine is currently being...
in the human.
In non-mammalian animals, the zona pellucida (called vitelline layer) plays an important role in preventing cross-breeding of different species, especially in species that fertilize outside of the body (e.g. fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
).
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
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
, Porcine zona pellucida
Porcine zona pellucida
Porcine zona pellucida is a form of zona pellucida extracted from the ovaries of pigs, often referred to by the initials PZP.The zona pellucida is a thick membrane that surrounds the unfertilized eggs of mammals. In order for an egg to be fertilized, sperm must first bind to, and then penetrate the...
is used to keep deer
Deer
Deer are the ruminant mammals forming the family Cervidae. Species in the Cervidae family include white-tailed deer, elk, moose, red deer, reindeer, fallow deer, roe deer and chital. Male deer of all species and female reindeer grow and shed new antlers each year...
populations low, and this process is commonly referred to as "spay-vac".
Zona pellucida glycoproteins
There are four major zona pellucida glycoproteins, termed ZP1-4. ZP1, ZP3ZP3
Zona pellucida sperm-binding protein 3, also known as zona pellucida glycoprotein 3 or the sperm receptor, is a protein that in humans is encoded by the ZP3 gene...
and ZP4
ZP4
Zona pellucida sperm-binding protein 4 is a protein that in humans is encoded by the ZP4 gene.- Function :The zona pellucida is an extracellular matrix that surrounds the oocyte and early embryo. It is composed primarily of three or four glycoproteins with various functions during fertilization and...
bind to capacitated spermatozoa and induce the acrosome reaction
Acrosome reaction
During fertilization, a sperm must first fuse with the plasma membrane and then penetrate the female egg in order to fertilize it. Fusing to the egg usually causes little problem, whereas penetrating through the egg's hard shell can present more of a problem to the sperm...
.Successful fertilization depends on the ability of sperm to penetrate extracellular matrix surrounding eggs.
In the mouse:
- ZP3ZP3Zona pellucida sperm-binding protein 3, also known as zona pellucida glycoprotein 3 or the sperm receptor, is a protein that in humans is encoded by the ZP3 gene...
allows species-specific sperm binding - ZP2 mediates subsequent sperm binding
- ZP1 cross-links ZP2 and ZP3.
Data with native human protein is not currently available.
Further reading
- Bagnell C (2005). "Animal Reproduction". Rutgers University Department of Animal Sciences.
