The project is to study the possible role of the redundant nuclear envelope (RNE) in the calcium-dependent regulation of sperm movement. This structure is found in the headpiece of mammalian sperm and appears to be the excess vestments of the nuclear envelope after compaction of the nucleus during sperm development. Although the RNE has been considered by many to be merely a waste product, preliminary evidence suggests it is a calcium storage site which releases calcium to hyperactivate sperm in the female oviduct. This idea is supported by the close proximity of the envelope to the flagellar base and the mitochondrion in the sperm head where the signal for flagellar beating arises. In addition, immunofluorescence light microscopy has revealed that inositol triphosphate (IP3) receptors are found in the region of the RNE. When activated, IP3 receptors in other cell systems normally cause release of calcium from intracellular stores. Two specific objectives are proposed for this project to substantiate this function of the RNE. As the first objective, immunogold electron microscopy will be used to demonstrate unequivocally that IP3 receptors are located on the membranes of the RNE. As the second objective, well characterized pharmacological agents will be employed to cause intracellular calcium release in order to analyze the role of internal calcium, presumably from the RNE, in control of sperm activation.
