Presence of polysialic acid and HNK-1 carbohydrate on brain glycoproteins from beta-1,4-galactosyltransferase-knockout mice.

Polysialic acid and HNK-1 carbohydrate are expressed on Gal beta 1-->4GlcNAc outer chains of N-linked sugar chain of neural cell recognition molecules at certain developmental stages and involved in neural tissue formation. Targeted inactivation of the mouse beta-1,4-galactosyltransferase (beta-1,4-GalT) gene resulted in short life of the mice which supposedly do not have such carbohydrate antigens but have no defects in neural tissue formation. Analysis of the mutant mouse brain glycoproteins revealed that polysialic acid and HNK-1 carbohydrate are normally expressed in an age-dependent manner. In support of this, protein bands reacted with Ricinus communis agglutinin-I, which interacts with oligosaccharides terminated with the Gal beta 1-->4GlcNAc group, and beta-1,4-GalT activity toward GlcNAc beta-S-pNP were detected in the mutant mouse brain, indicating that brain contains another functional beta-1,4-GalT important for the expression of the carbohydrate antigens.