Cell surface glycosylation diversity of embryonic thymic tissues

In the thymus, glycosylation status of many cell surface molecules changes during the thymocyte maturation and selection processes. In this study, we evaluated the glycosylation changes and possible relationships with programmed cell death in the thymic tissues from mouse embryos at the days 14 (E14), 15 (E15), 16 (E16), 17 (E17) and 18 (E18) of embryonic development. In order to determine glycosylation changes we used three different plant Lectins: peanut agglutinin (PNA), Moackia amurensis leucoagglutinin (MAL or MAAI) and Sombucus nigra agglutinin (SNA), which recognize core disaccharide galactose (1-3) N-acetylgalactosamine [Gal beta(1 -> 3)GalNAc], siatic acid linked (2 -> 3) to galactose [SA alpha(2 -> 3)Gal] and siatic acid linked to galactose [SA)alpha(2 -> 6)Gal] structures, respectively. Our lectin histochemistry and lectin blotting studies indicated that glycosylation pattern was modified in thymocytes at the embryonic developmental. stages analyzed. The immature cortical thymocytes were labeled by PNA, whereas medullary thymocytes were positive for MAL and SNA binding. Many medullary thymocytes exhibited alpha(2 -> 6)-linked siatic acid on their surface and this increased throughout the gestational stages. In the lectin blotting studies, different protein bands of various molecular weights were identified in thymocytes. Two of them were putatively identified as CD43 and CD45 glycoproteins. In addition, TUNEL (deoxynucleotdyltransferase-mediated dUDP nick end labeling) indicated that only PNA-positive cortical thymocytes were deleted in all embryonic stages. These results indicate that the glycosylation pattern was modified in thymocytes at all embryonic developmental stages, and these modifications can affect the T cell deletion, probably via the galectin-1 molecule in the embryonic thymus. (C) 2007 Elsevier GmbH. All. rights reserved.