Recognition Mechanism of Egg and Sperm Based on Sugar Chains

What is it about?

Recognition between sperms and eggs is required for species maintenance in organisms. Eggs are covered in an egg extracellular matrix, which contains considerable amounts of glycoprotein. This matrix usually possesses a site that prevents the recognition of sperms, which protect the egg against an attack from foreign bodies such as bacteria. The sperm is induced by a component of the egg extracellular matrix and is attached to the latter. The sperm increases the [pH]i and [Ca2+]i on receiving a signal from the egg extracellular matrix and evokes exocytosis of the acrosomal vesicle at the tip of the sperm head (acrosome reaction). It then passes through the egg extracellular matrix and the vitelline membrane, and arrives at the egg cell membrane. Only the new sperm cell membrane, which is detached due to the exocytosis, can fuse with the egg cell membrane. A sugar chain is known to play an important role in the acrosome reaction and in the binding between the egg and the sperm.

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