Characterization of the Polysialylation Status in Ovaries of the Salmonid Fish and the Percid Fish .

In vertebrates, the carbohydrate polymer polysialic acid (polySia) is especially well known for its essential role during neuronal development, regulating the migration and proliferation of neural precursor cells, for instance. Nevertheless, sialic acid polymers seem to be regulatory elements in other physiological systems, such as the reproductive tract. Interestingly, trout fish eggs have polySia, but we know little of its cellular distribution and role during oogenesis. Therefore, we localized α2,8-linked -acetylneuraminic acid polymers in the ovaries of by immunohistochemistry and found that prevalent clusters of oogonia showed polySia signals on their surfaces. Remarkably, the genome of this salmonid fish contains two genes and one gene, that is, three polysialyltransferases. The expression analysis revealed that for , 60 times more mRNA was present than and . To compare polysialylation status regarding various polySiaT configurations, we performed a comparable analysis in . The genome of this perciform fish contains only one and no gene. Here, too, clusters of oogonia showed polysialylated cell surfaces, and we detected high mRNA values for . These results suggest that in teleosts, polySia is involved in the cellular processes of oogonia during oogenesis.