The male seahorse synthesizes and secretes a novel C-type lectin into the brood pouch during early pregnancy.

The male seahorse incubates its young in a manner resembling that of a mammalian pregnancy. After the female deposits her eggs into the male's brood pouch they are fertilized and the embryos develop and grow for several weeks until they are able to withstand the external environmental conditions independently, at which point they are irreversibly released. Although the precise function of the brood pouch is not clear, it is probably related to providing a suitable protective and osmotic environment for the young. The aim of this project was to construct and characterize a cDNA library made from the tissue lining the pouch, in order to help understand the molecular mechanisms regulating its development and function. The library profile indicates expression of genes encoding proteins involved in metabolism and transport, as well as structural proteins, gene regulatory proteins, and other proteins whose function is unknown. However, a large portion of the library contained genes encoding C-type lectins (CTLs), of which three full-length proteins were identified and found to contain a signal peptide and a single C-lectin domain, possessing all the conserved structural elements. We have produced recombinant protein for one of these and raised antisera; we have shown, using Western analysis and 2D electrophoresis, that this protein is secreted in significant quantities into the pouch fluid specifically during early pregnancy. Preliminary functional studies indicate that this CTL causes erythrocyte agglutination and may help to repress bacterial growth.