DEVELOPMENTAL EXPRESSION OF 2 RAT SIALYLTRANSFERASES THAT MODIFY THE NEURAL CELL-ADHESION MOLECULE, N-CAM

Polysialylation of the neural cell adhesion molecule (N-CAM) reduces t he efficacy of N-CAM-mediated hemophilic binding and is regulated both during development and in regions undergoing neurogenesis or remodeli ng in the adult. Hamster PST-1 (PST) and rat STX are two related sialy ltransferases that catalyze the polysialylation of N-CAM. We have isol ated a cDNA clone for the rat homologue of PST and compared its amino acid and nucleotide sequence to that of rat STX. This analysis reveale d regions of high sequence similarity corresponding to the enzymatic d omains of the two molecules. Other regions of lower similarity were us ed to generate specific probes for in situ hybridization. The distribu tion of PST and STX mRNAs, polysialic acid, and N-CAM were analyzed at three developmental stages. PST and STX mRNAs were expressed abundant ly throughout the nervous system at embryonic day 15 and postnatal day 4 and were coexpressed in most tissues examined. In the adult brain, STX expression was reduced relative to PST and expression of both mRNA s was restricted to subsets of cells in areas undergoing constant syna ptic rearrangement including hippocampus and olfactory system. The res ults suggest that both PST and STX participate in the polysialylation of N-CAM in vivo and that their expression levels are dynamically cont rolled during development and regeneration. (C) 1997 Elsevier Science B.V.