Monday, April 04, 2005

Enter, Izumo

Let's face it, everything about the creation of a human self -- body and soul -- is astonishing, which is perhaps why vitality and soul were for so long explained as nonmaterial manifestations of the supernatural. But as we learn more and more about conception, embryogenesis and consciousness, the more we realize that even the most apparently miraculous aspects of self are susceptible of natural explanations.

Consider the fertilization of an egg by a sperm. One sperm of millions manages to penetrate an egg's outer coat, the zona pellucida. Instantly, the coat becomes impenetrable to other sperms. How does this marvel of selective admittance work?

In a recent issue of Nature, Japanese researchers working with mice announced the discovery of a protein -- named Izumo, after the Japanese shrine to marriage -- that seems to be an essential "key" to sperm egg-fusion. The precise protein on the egg's inner plasma membrane that Izumo binds to has yet to be determined, as is the nature of the subsequent chemical cascade that seals the zona pellucida to further entry.

Step by step, the marvelous story of a human beginning is unraveled -- not miraculous, to be sure, but the geometry of proteins.