The activation of the unique protein Catsper - provides which special property to human sperms?
Ans. B. Progressive motilitya. Spermatozoa leaving the testes are not fully mobile. They continue their maturation and acquire motility during their passage through the epididymis. Motility is obviously important in vivo, but fertilization occurs in vitro if an immotile spermatozoon from the head of the epididymis is microinjected directly into an ovum. The ability to move forward (progressive motility), which is acquired in the epididymis, involves activation of a unique protein called CatSper, which is localized to the principal piece of the sperm tail.b. This protein appears to be a Ca2+ ion channel that permits cAMP-generalized Ca2+ influx. In addition, spermatozoa express olfactory receptors, and ovaries produce odorant-like molecules. Recent evidence indicates that these molecules and their receptors interact, fostering movement of the spermatozoa toward the ovary (chemotaxis).c. Ejaculation of the spermatozoon involves contractions of the vas deferens mediated in part by P2X receptors, ligand gated cation channels that respond to ATP (see Chapter 7), and fertility is reduced in mice in which these receptors are knocked out.d. Once ejaculated into the female, the spermatozoa move up the uterus to the isthmus of the uterine tubes, where they slow down and undergo capacitation. This further maturation process involves two components: increasing the motility of the spermatozoa and facilitating their preparation for the acrosome reaction. However, the role of capacitation appears to be facilitatory rather than obligatory, because fertilization is readily produced in vitro. From the isthmuses the capacitated spermatozoa move rapidly to the tubal ampullas, where fertilization takes place.
Capacitation
Progressive motility
Glycolysis
Ovum wall penetration
Endocrinology and Reproduction