KGT: O-linked glycan expression during Drosophila development

Mucin-type O-linked glycosylation is an evolutionarily conserved protein modification that is essential for viability in Drosophila melanogaster. However, the exact role of O-glycans and the identity of the crucial apoproteins modified with O-linked N-acetylgalactosamine (O-GalNAc) remain unknown. In an effort to elucidate the O-linked glycans expressed during Drosophila development, we have employed fluorescent confocal microscopy using a battery of lectins and an antibody specific for the GalNAca–Ser/Thr structure (Tn antigen). Confocal microscopy provides high-resolution images of thediversityof glycans expressed inmanydeveloping organ systems. Inparticular,O-glycansarehighlyexpressedon a number of ectodermally derived tissues such as the salivary glands, developing gut, and the tracheal system, suggesting a role for O-glycans in cell polarity and tube formation common to these organs. Additionally, O-glycans are found in the developing nervous system and within subregions of developing tissues known to be active in cell signaling events. This study provides us with temporal and spatial information regarding O-glycan expression as well as a set of reagents for the isolation of glycoproteins from specific developmental stages and organ systems. This information will aid us in identifying the in vivo substrates of the UDP– GalNAc: polypeptide N-acetylgalactosaminyltranferases, in a continuing effort to define the biological role of O-linked glycoproteins during development. Key words: development/Drosophila/glycosylation/lectins/ pgan