What is a Zona Pellucida?

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The Zona Pellucida is a glycoprotein (ZP3) membrane surrounding the plasma membrane of an oocyte. Glyco proteins are proteins attached to the poly-peptide (short polymers of amino acids linked by peptide bonds) side chains. Simply, glycoprotein is a conjugated protein having a carbohydrate component. Plasma membrane is a biological cell membrane that separates the interior of all cells from the outside environment. Oocyte is a female reproductive cell. Zona Pellucida binds sperm and is vital for the acrosome reaction, which helps a sperm penetrate the egg cell during fertilization. Acrosome is a specialized organelle found on sperm cells. It wraps around the head of the sperm and contains enzymes designed to help the sperm penetrate the egg by breaking down the proteins in the egg’s cell wall. In the process of acrosome reaction, the sperm cell fuses with the egg, releases the enzymes, enters the egg to complete fertilization.

What is the role of Zona Pellucida?

An egg cell, like all animal cells, is surrounded by a plasma membrane, which protects the intracellular components and regulates the materials that go in and out of the cell. The Zona Pellucida is located just outside the egg cell’s plasma membrane and is important part of it. It is composed of 3 glyco proteins, ZP1, ZP2 and ZP3. The role of each of them is as follows.

•  ZP3 allows for species specific sperm binding, avoiding the sperm of a dissimilar species from fertilizing the egg.
•  ZP3 is mainly imperative for animals that have external fertilization, for instance fish.
•  ZP2 mediates sperm binding.
•  ZP1 is crucial for the structural integrity of the Zona Pellucida.

What is the process of Fertilization?

During fertilization, the Zona Pellucida binds the sperm by sticking to proteins on its plasma membrane. When this occurs, the acrosome, an organelle on the tip of the sperm’s head, opens and releases enzymes (biological catalysts) and antigens (molecule recognized by the immune system) facilitating it to break through the touch plasma membrane of the oocyte. When a sperm experiences the acrosome reaction and breaks through the egg’s plasma membrane, fertilization happens. After fertilization, the Zona Pellucida dies and shed in a phenomenon called “Zona hatching”. The Zona Pellucida is also essential for egg cell death in ceases when there is no fertilization.

What is the responsibility of Zona Pellucida in Immuno contraception?

•  Glyco proteins in ZP1, 2, 3 and 4 are targets for immuno contraception in the human.
•  In non-mammalian animals, the Zona Pellucida called the vitellina layer, palys a major role in preventing cross-breeding of various species, particularly in species that fertilize outside the body like fish.
•  Zona Pellucida is commonly used to control wildlife population problems by immuno contraception. When Zona Pellucida of one animal is injected into the blood stream of another, it results in sterility of the second species due to immune response. This effect is temporary or permanent depending on the method used. In New Jersey, Porcine Zona Pellucida, the Zona Pellucida extracted from the ovaries of pigs, is used to keep deer populations low. And this process is generally referred to as “spray-vac”.

Why Male infertility occurs?

Male infertility is sometimes due to sperm that fail to undergo the acrosome reaction. On the contrary, in some species, some release the fillings of their acrosome before reaching the egg, removing their own chance of fertilizing the egg, but increasing the motility of the other sperm. Premature acrosome reaction is most common in species in which females have many sexual partners, which results in high contest for the sperm.

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