Elucidation of individual roles of the galactosyl|ransferase gene family using gene knockout mice

细胞与细胞之间的相互作用对于细胞生长和分化是重要的。通过细胞表面碳水化合物的相互作用是其中不可或缺的机制之一。我们通过建立β-1.4-半乳糖转移酶-I（β4GalT-I）基因敲除小鼠模型，研究了碳水化合物在体内的作用。β4GalTs基因家族由7个基因组成，每个基因都有自己的功能，我们对β4GalT-I基因敲除小鼠的糖链结构进行了详细的分析。通过测定β 1，4-连接上的Gal残基，估计了β4GalT-I基因对不同细胞类型碳水化合物生物合成的贡献。接下来，在β4GalT-I KO小鼠中分析了已知由β 4GalT和其他糖基转移酶合成的选择素的碳水化合物配体。并估算了β4GalT-I基因对它们生物合成的贡献。此外，还检测了β4GalT-I KO小鼠的炎症反应以及β4GalT-I缺乏的影响。此外，检查了β4GalT-I缺乏对皮肤伤口愈合的影响。我们的研究结果表明，β4GalT-I在选择素糖配体的生物合成中起重要作用，它们的缺乏导致β4GalT-I KO小鼠的炎症反应减少和伤口愈合延迟，而这些结果是使用混合遗传背景的β4GalT-I KO小鼠获得的，我们发现近交系背景的β4GalT-I KO小鼠在胚胎发育后期是致命的。由于在胚胎死亡前几天，胎盘而不是胚胎的生长迟缓是显著的，因此胎盘缺陷被认为是胚胎死亡的原因。由于致死率随遗传背景而变化的原因可能是其他β 4GalT的代偿活性，因此产生了另一个β4GalT基因缺陷的基因敲除小鼠。阐明这些p4 GalT基因的作用的研究正在进行中。

Cell-to-cell, interactions are important for cell growth and differentiation. The interaction through cell surface carbohydrates is one of indispensable mechanisms among them. We have been studying on the role of carbohydrates in vivo by generating a gene knockout mouse deficient in β-1.4-galactosyhransferase-I(β4GalT-I). β4GalTs are recently found to form the gene family consisting of 7 genes, which have their own roles.We analyzed carbohydrate structures of β4GalT-I KO mice in detail. Contribution of β4GalT-I gene to the biosynthesis of carbohydrates of various cell types was estimated by measuring Gal residues in the β1,4-linkage. Next, carbohydrate ligands of selectins, which are known to be synthesized by β4GalTs and other glycosyltransferases, were analyzed in β4GalT-I KO mice. Contribution of β4GalT-I gene to their biosynthesis was also estimated. Furthermore, Inflammatory responses of β4GalT-I KO mice and the effect of β4GalT-I deficiency were examined. In addition, the effect of β4GalT-I deficiency on skin wound healing was examined. Our results indicated that β4GalT-I plays an important role in the biosynthesis of carbohydrate ligands of selectins and their deficiency results in reduction of inflammatory responses and delayed wound healing in β4GalT-I KO mice.While these results were obtained using β4GalT-I KO mice on mixed genetic backgrounds, we found β4GalT-I KO mice on inbred background to be lethal during late embryogenesis. Since growth retardation of the placenta rather than the embryo was remarkable several days before its death, the defect of placenta was suggested to be a cause of the embryonic lethality. Since the reason of changeable lethality depending on genetic background might be a compensatory activity by other β4GalTs, gene knockout mice deficient in another β4GalT gene were generated. Studies on elucidating the role of these p4GalT genes are in progress.