A transgenic mouse line with alpha-1,3/4-fucosyl-transferase cDNA: production and characteristics

A Novel Human Gal-3-O-Sulfotransferase

Based on sequence homology with the previously cloned human cerebroside sulfotransferase (CST) cDNA, a novel sulfotransferase was cloned by screening a human fetal brain cDNA library. The novel sulfotransferase gene was present on human chromosome 11q13; the location was different from human CST and from that of the recently cloned human beta-Gal 3'-sulfotransferase (GP3ST). The isolated cDNA contained an open reading frame that encoded a predicted protein of 431 amino acid residues with type II transmembrane topology. The amino acid sequence showed 33% identity with that of human CST and 38% with that of human GP3ST. The recombinant enzyme expressed in Chinese hamster ovary cells catalyzed transfer of sulfate to position 3 of non-reducing beta-galactosyl residues in Galbeta1-4GlcNAc. Type 2 chains served as good acceptors, whereas type 1 chains served as poor acceptors, and intermediate activity was found toward Galbeta1-3GalNAc. Therefore, the substrate specificity was different from that of GP3ST. CST activity was not detected in the newly cloned enzyme. Northern blotting analysis showed that the sulfotransferase mRNA was strongly expressed in the thyroid and moderately expressed in the brain, heart, kidney, and spinal cord. Co-transfection of the enzyme cDNA and fucosyltransferase III into COS-7 cells resulted in expression of (SO(4)-3)Galbeta1-4(Fucalpha1-3)GlcNAc and a small amount of (SO(4)-3)Galbeta1-3(Fucalpha1-4)GlcNAc. These results indicated that the newly cloned enzyme is a novel Gal-3-O-sulfotransferase and is involved in biosynthesis of the (SO(4)-3)Galbeta1-4(Fucalpha1-3)GlcNAc structure.

Creating and maintaining the gastrointestinal ecosystem: what we know and need to know from gnotobiology

Studying the cross talk between nonpathogenic organisms and their mammalian hosts represents an experimental challenge because these interactions are typically subtle and the microbial societies that associate with mammalian hosts are very complex and dynamic. A large, functionally stable, climax community of microbes is maintained in the murine and human gastrointestinal tracts. This open ecosystem exhibits not only regional differences in the composition of its microbiota but also regional differences in the differentiation programs of its epithelial cells and in the spatial distribution of its component immune cells. A key experimental strategy for determining whether "nonpathogenic" microorganisms actively create their own regional habitats in this ecosystem is to define cellular function in germ-free animals and then evaluate the effects of adding single or several microbial species. This review focuses on how gnotobiotics-the study of germ-free animals-has been and needs to be used to examine how the gastrointestinal ecosystem is created and maintained. Areas discussed include the generation of simplified ecosystems by using genetically manipulatable microbes and hosts to determine whether components of the microbiota actively regulate epithelial differentiation to create niches for themselves and for other organisms; the ways in which gnotobiology can help reveal collaborative interactions among the microbiota, epithelium, and mucosal immune system; and the ways in which gnotobiology is and will be useful for identifying host and microbial factors that define the continuum between nonpathogenic and pathogenic. A series of tests of microbial contributions to several pathologic states, using germ-free and ex-germ-free mice, are proposed.

Distribution of the CD15 epitope in the mammalian developing lung is opposite in mouse compared with human

The distribution of the expression of the CD15 epitope was characterized by immunohistochemistry in the developing mouse and human lung on embryonic days E9.5-E19 and gestational weeks GW7-GW25, respectively. In the earliest stages in the mouse, the tracheal epithelial cells expressed CD15 on their apical and lateral cell membranes and, in the more proximal regions, also showed a faint cytoplasmatic CD15 expression. Only very few epithelial cells in the bronchial bud regions expressed CD15 on their apical surfaces. In later stages (E12-E17), cells in the proximal parts of the bronchi and bronchioli expressed CD15 on their apical, but also on their lateral membranes, and increasing numbers of cells expressed CD15 cytoplasmatically. Cells in the distal, presumably proliferating, areas of the bud regions were CD15 negative. This distribution pattern of CD15 was consistent until the latest embryonic stages. These results are completely opposite to those found in human developing lung where up to GW20 bronchial and bronchiolar bud regions were CD15 positive, while in the proximal parts of the airways the vast majority of cells were CD15 negative. After GW20, CD15 immunoreactivity in the bud regions vanished and was completely absent on GW25. This difference between human and mouse adds further evidence to profound species differences in the expression of CD15 in various organs, e.g., in the cerebellum or the retina, and should be taken into account when considering functional roles of CD15 and also when relating results from a (transgenic) mouse model to the respective human organ system.