Developmentally regulated oligosialylation pattern inebrafish embryogenesis
Date Issued
2008
Date
2008
Author(s)
CHANG, Lan-Yi
Abstract
The nine-carbon sugar, sialic acid, plays important roles as the recognition epitopes in cell-cell communications. Its regulated expression often reflects the status of a cell, and has been reported as stage-specific antigen for tumorigenesis or embryogenesis. In this thesis work, theiological functions of developmentally regulated sialylation, particularly in relation to the spatial and temporal regulated expression of α2-8 sialyltransferases (ST8sia) during the embryogenesis of Zebrafish, was investigated using a combination of chemical and mass spectrometry (MS) analyses. Glycomic survey mapping followed by advanced glycan sequencing were first performed across the different developmental stages of fertilized Zebrafish eggs. Among the unusual structures identified are the complex type N-glycans that carry β4-galactosylated sialyl Lewis X, the disialylated O-glycans, Fucα1-3GalNAcβ1-4NeuAc/NeuGcα2-3Galβ1-3GalNAc, and the oligosialylated glycolipids. The stage-specific, distinctive Neu5Ac/Neu5Gc sialylation patterns observed then prompted a more precise quantification of the respective oligosialylation by fluorescent chromatography after chemical derivatization. Interestingly, the oligosialic acids of glycoproteins were found to decrease whereas those of glycolipids increased along the embryogenesis. To determine if the observed profiles are due to the regulation of biosynthesis or catabolism, or both, the transcripts of all inferred Zebrafish ST8Sia genes responsible for the biosynthesis of oligosialylation were quantitatively mapped by real-time PCR, and the activity of endogenous sialidases were assayed, for each of the developmental stages. The presence of sialidases and an increased level of expression of all the ST8Sia genes led to a working model, which proposes that the oligosialic acids from glycoproteins are maternally inherited (synthesized before fertilization) and exocytosis out of the embryo into the perivitelline space where it undergoes catabolism, whereas oligosialic acids on the glycolipids are de novo synthesized by the increasingly expressed ST8Sia in the embryos. Furthermore, through whole mount in-situ hybridization, most of the ST8Sia genes were shown to be expressed in the nervous system during early embryogenesis, with different onset and locations. In summary, the precise MS and MS/MS-based glycomic profiles, together with detailed structural determination, quantitative analysis of the developmentally regulated oligosialylation pattern, and the spatial and temporal expression profiling of ST8Sia of Zebrafish, collectively provides new sialoglycobiology insights for neuroscientists at the molecular level and highlighted the significance and complicated regulation of oligosialylation in early neuronal development.
Subjects
sialic acid
oligosialylation
Zebrafish
glycomic
developmental
mass spectrometry
File(s)![Thumbnail Image]()
Loading...
Name
ntu-97-D93b46006-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):4402db1e56b5d1bbff4ec1d13cd07eb3