| Research Abstract |
On the studies of sperm chemotaxis and activation in the ascidians Ciona 1) molecular structure of sperm-activating and -attracting factor (SAAF) originated from the eggs was determined using NMR and MS/MS methods. The factor is the novel steroid : (3R,4R,7R,25S)-3,4,7,26-tetrahydroxycholestane-3,26-disulfate. The steroid was synthesized and it was demonstrated that nanomolar concentration could activate and attract the ascidian sperm. 2) In the cell signaling for the sperm chemotaxis, it was demonstrated that stor-operated calcium channel plays key role for the phenomenon. Furthermore, a numerical studies showed that two different strategies cause sperm chemotaxis in the ascidians and siphonophores. 3) In the cell, signaling for the activation of ascidian sperm, It was demonstrated that calcium/calmodulin/calmoduline kinase system activates K^+ channel and resulting membrane hyperpolarization causes cAMP increase, resulting in the activation of sperm motility through phosphorylation of axonemal proteins. 4) On the studies of sperm activation in the Pacific hering Clupea pallasi, participation of reversed Na^+/Ca^<2+> exchanger was clarified. 5) On the cell signaling for the, initiation of sperm motility in the salmonid fish, cAMP-dependent protein kinase catalytic subunit was characterized. Furthermore, the 15kDa protein, which is known to be indispensable for the initiation of flagellar motility, was purified, and it's characterized. The acrosome reaction of spermatozoa was first found in amphioxus in the world, and participation of GTP-anchored protein in the acrosome reaction was also first found the mussel, Mytilus edulis.
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