The Functional Glycomics Gateway (http://www.functionalglycomics.org/fg/) は新たな糖鎖の機能や解析方法などを掲載しているホームページであり、Nature Publishing Groupと Consortium for Functional Glycomicsが共同して作製している。
この中で、一月に２報ずつNature Publishing Groupが論文を抽出し、Featured Articlesとしてその内容と糖鎖研究に与えるインパクトについて掲載しています。
今回、分子生理研究部門の
Ishii A, Ikeda T, Hitoshi S, Fujimoto I, Torii T, Sakuma K, Nakakita S, Hase S, Ikenaka K. Developmental changes in the expression of glycogenes and the content of N-glycans in the mouse cerebral cortex. Glycobiology. 2007 Mar;17(3):261-76.
が取り上げられました。
Brain development: Changing cortex, changing glycans
A new approach to glycosylation profiling uncovers the glycan changes in the developing mouse cortex.
By how much does cell surface glycosylation differ between organs and between different stages of development? Finding an answer to this question is a primary goal of glycomics, and at the same time it is a complex experimental task. Firstly, glycosylation profiling through the quantification of glycosyltransferase gene expression levels is difficult because these are often poorly expressed genes. In a previous study, researchers measured the differences between transferase mRNA amounts in murine tissues using a glycogene chip derived from a commercially available cDNA microarray. A new study by Ishii et al. in Glycobiology describes a different cDNA array design. Similar to the earlier study, the authors quantified the amount of glycans present on the cells by chemical analysis. Using this and their new array together, Ishii et al. were now able to detect changes in glycosylation during the development of the mouse cortex.
Ishii et al. compared the cerebral cortices from mice at 5 different time points during embryonal and neonatal development. While conducting their analysis, they realized that the previously created cDNA glycochip was not sufficiently sensitive for the fluorometrical determination of expression levels; furthermore, some glycogenes were missing on this chip. The authors therefore designed a new glycogene macroarray from mouse and homologous human sequences and monitored transferase expression by autoradiography. Ishii et al. found that during development, glycogene expression in the mouse cortex changed by as much as 4-fold; among the genes whose expression changed, α2,8 sialyltransferase II reached its maximum in the cortex of the newborn mouse, after which it decreased to almost nothing by 12 weeks after birth.
Structural analysis by high pressure liquid chromatography allowed the identification of 70% of the total N linked sugar chains. Lewis X glycans - which contain a terminal α1-3 fucose - increased 2-fold during development; interestingly, mice lacking the corresponding fucosyltransferase were only recently shown to have severe behavioral impairments. Futhermore, Ishii et al. observed that the abundance of various N-glycans containing a high number of mannose residues changed drastically in the examined period of time. This result lends support to the hypothesis that this type of N-glycans participates in the formation of synapses during cortex development. Combining expression quantification and N-glycan analysis, the authors were able to construct a pathway of enzymes participating in N glycan formation in the mouse brain.
In summary, by using genetic and chemical analysis in parallel, the study of Ishii et al. uncovers glycosylation changes during development. Further refinement of the genetic profiling described in this study might increase the resolution of the expression screening, thus allowing the analysis of cell subpopulation glycosylation in specific organs. Using refined tools and performing data meta-analysis may more and more reveal the physiological relevance of the changes in glycosylation during development.
Mirko von Elstermann
Functional Glycomics Gateway
Ishii A. et al.
Developmental changes in the expression of glycogenes and the content of N-glycans in the mouse cerebral cortex
Glycobiology 17, 261 - 276 (2007).
http://glycob.oxfordjournals.org/cgi/content/abstract/17/3/261 |
