Selectin Dependence of Allergic Skin Inflammation Is Diminished by Maternal Atopy

Allergic skin inflammation requires the influx of inflammatory cells into the skin. Extravasation of leukocytes into the skin requires interactions between endothelial selectins and their glycan ligands on the surface of leukocytes. Selectin-ligand formation requires the activity of several glycosyltransferases, including Fut7 In this report, we tested the importance of Fut7 for the development of allergic skin inflammation in the Stat6VT transgenic mouse model. We observed that Fut7 deficiency was protective but did not eliminate disease. Segregation of the data by gender of the parent that transmitted the Stat6VT transgene, but not by gender of the pups, which were analyzed for disease, revealed that the protective effects of Fut7 deficiency were significantly greater when dams were Stat6VT negative. In contrast, in mice from litters of Stat6VT+ dams, Fut7 deficiency resulted in only modest protection. These findings indicate that pups from atopic dams exhibit a greater propensity for allergic disease, similar to observations in humans, and that the effect of maternal atopy is due to enhanced selectin-independent mechanisms of leukocyte recruitment in their offspring. Together, these results demonstrate that Fut7 deficiency can be protective in a model of atopic dermatitis but that maternal atopy diminishes these protective effects, suggesting alternative pathways for leukocyte recruitment in the absence of Fut7 enzyme activity. These observations have implications for understanding how the environment in utero predisposes for the development of allergic disease.

Gut microbiota-mediated lysophosphatidylcholine generation promotes colitis in intestinal epithelium-specific Fut2 deficiency

BACKGROUND AND AIMS

Previous study disclosed Fucosyltransferase 2 (Fut2) gene as a IBD risk locus. This study aimed to explore the mechanism of Fut2 in IBD susceptibility and to propose a new strategy for the treatment of IBD.

METHODS

Intestinal epithelium-specific Fut2 knockout (Fut2△IEC) mice was used. Colitis was induced by dextran sulfate sodium (DSS). The composition and diversity of gut microbiota were assessed via 16S rRNA analysis and the metabolomic findings was obtained from mice feces via metabolite profiling. The fecal microbiota transplantation (FMT) experiment was performed to confirm the association of gut microbiota and LPC. WT mice were treated with Lysophosphatidylcholine (LPC) to verify its impact on colitis.

RESULTS

The expression of Fut2 and α-1,2-fucosylation in colonic tissues were decreased in patients with UC (UC vs. control, P = 0.036) and CD (CD vs. control, P = 0.031). When treated with DSS, in comparison to WT mice, more severe intestinal inflammation and destructive barrier functions in Fut2△IEC mice was noted. Lower gut microbiota diversity was observed in Fut2△IEC mice compared with WT mice (p < 0.001). When exposed to DSS, gut bacterial diversity and composition altered obviously in Fut2△IEC mice and the fecal concentration of LPC was increased. FMT experiment revealed that mice received the fecal microbiota from Fut2△IEC mice exhibited more severe colitis and higher fecal LPC concentration. Correlation analysis showed that the concentration of LPC was positively correlated with four bacteria-Escherichia, Bilophila, Enterorhabdus and Gordonibacter. Furthermore, LPC was proved to promote the release of pro-inflammatory cytokines and damage epithelial barrier in vitro and in vivo.

CONCLUSION

Fut2 and α-1,2-fucosylation in colon were decreased not only in CD but also in UC patients. Gut microbiota in Fut2△IEC mice is altered structurally and functionally, promoting generation of LPC which was proved to promote inflammation and damage epithelial barrier.

Intestinal α1-2-Fucosylation Contributes to Obesity and Steatohepatitis in Mice

BACKGROUND & AIMS

Fucosyltransferase 2 (Fut2)-mediated intestinal α1- 2-fucosylation is important for host-microbe interactions and has been associated with several diseases, but its role in obesity and hepatic steatohepatitis is not known. The aim of this study was to investigate the role of Fut2 in a Western-style diet-induced mouse model of obesity and steatohepatitis.

METHODS

Wild-type (WT) and Fut2-deficient littermate mice were used and features of the metabolic syndrome and steatohepatitis were assessed after 20 weeks of Western diet feeding.

RESULTS

Intestinal α1-2-fucosylation was suppressed in WT mice after Western diet feeding, and supplementation of α1-2-fucosylated glycans exacerbated obesity and steatohepatitis in these mice. Fut2-deficient mice were protected from Western diet-induced features of obesity and steatohepatitis despite an increased caloric intake. These mice have increased energy expenditure and thermogenesis, as evidenced by a higher core body temperature. Protection from obesity and steatohepatitis associated with Fut2 deficiency is transmissible to WT mice via microbiota exchange; phenotypic differences between Western diet-fed WT and Fut2-deficient mice were reduced with antibiotic treatment. Fut2 deficiency attenuated diet-induced bile acid accumulation by altered relative abundance of bacterial enzyme 7-α-hydroxysteroid dehydrogenases metabolizing bile acids and by increased fecal excretion of secondary bile acids. This also was associated with increased intestinal farnesoid X receptor/fibroblast growth factor 15 signaling, which inhibits hepatic synthesis of bile acids. Dietary supplementation of α1-2-fucosylated glycans abrogates the protective effects of Fut2 deficiency.

CONCLUSIONS

α1-2-fucosylation is an important host-derived regulator of intestinal microbiota and plays an important role for the pathogenesis of obesity and steatohepatitis in mice.

Expanding the molecular and clinical phenotypes of FUT8-CDG

Pathogenic variants in the Golgi localised alpha 1,6 fucosyltransferase, FUT8, cause a rare inherited metabolic disorder known as FUT8-CDG. To date, only three affected individuals have been reported presenting with a constellation of symptoms including intrauterine growth restriction, severe delays in growth and development, other neurological impairments, significantly shortened limbs, respiratory complications, and shortened lifespan. Here, we report an additional four unrelated affected individuals homozygous for novel pathogenic variants in FUT8. Analysis of serum N-glycans revealed a complete lack of core fucosylation, an important diagnostic biomarker of FUT8-CDG. Our data expands both the molecular and clinical phenotypes of FUT8-CDG and highlights the importance of identifying a reliable biomarker for confirming potentially pathogenic variants.

FUT1 deficiency elicits immune dysregulation and corneal opacity in steady state and under stress

Fucosylation is a biological process that plays a critical role in multiple cellular functions from cell adhesion to immune regulation. Fucosyltransferases (FUTs) mediate fucosylation, and dysregulation of genes encoding FUTs is associated with various diseases. FUT1 and its fucosylated products are expressed in the ocular surface and ocular adnexa; however, the role of FUT1 in the ocular surface health and disease is yet unclear. Here, we investigated the effects of FUT1 on the ocular surface in steady-state conditions with age and under desiccating stress using a Fut1 knockout (KO) mouse model. We found that corneal epithelial defects and stromal opacity developed in Fut1 KO mice. Also, inflammatory responses in the ocular surface and Th1 cell activation in ocular draining lymph nodes (DLNs) were upregulated. Desiccating stress further aggravated Th1 cell-mediated immune responses in DLNs, lacrimal gland, and ocular surface in Fut1 KO mice, leading to severe corneal epithelial disruption and opacity. Mixed lymphocyte reaction assays revealed that the activity of splenocytes to stimulate CD4 T-cell proliferation was increased in Fut1 KO mice. Together, these data demonstrate that FUT1 deficiency induces immune dysregulation in the ocular surface and corneal opacity in steady state and under desiccating stress.

Std fimbriae-fucose interaction increases Salmonella-induced intestinal inflammation and prolongs colonization

Expression of ABO and Lewis histo-blood group antigens by the gastrointestinal epithelium is governed by an α-1,2-fucosyltransferase enzyme encoded by the Fut2 gene. Alterations in mucin glycosylation have been associated with susceptibility to various bacterial and viral infections. Salmonella enterica serovar Typhimurium is a food-borne pathogen and a major cause of gastroenteritis. In order to determine the role of Fut2-dependent glycans in Salmonella-triggered intestinal inflammation, Fut2+/+ and Fut2-/- mice were orally infected with S. Typhimurium and bacterial colonization and intestinal inflammation were analyzed. Bacterial load in the intestine of Fut2-/- mice was significantly lower compared to Fut2+/+ mice. Analysis of histopathological changes revealed significantly lower levels of intestinal inflammation in Fut2-/- mice compared to Fut2+/+ mice and measurement of lipocalin-2 level in feces corroborated histopathological findings. Salmonella express fimbriae that assist in adherence of bacteria to host cells thereby facilitating their invasion. The std fimbrial operon of S. Typhimurium encodes the π-class Std fimbriae which bind terminal α(1,2)-fucose residues. An isogenic mutant of S. Typhimurium lacking Std fimbriae colonized Fut2+/+ and Fut2-/- mice to similar levels and resulted in similar intestinal inflammation. In vitro adhesion assays revealed that bacteria possessing Std fimbriae adhered significantly more to fucosylated cell lines or primary epithelial cells in comparison to cells lacking α(1,2)-fucose. Overall, these results indicate that Salmonella-triggered intestinal inflammation and colonization are dependent on Std-fucose interaction.

The fucose salvage pathway inhibits invadopodia formation and extracellular matrix degradation in melanoma cells

The fucose salvage pathway is a two-step process in which mammalian cells transform L-fucose into GDP-L-fucose, a universal fucose donor used by fucosyltransferases to modify glycans. Emerging evidence indicates the fucose salvage pathway and the fucosylation of proteins are altered during melanoma progression and metastasis. However the underlying mechanisms are not completely understood. Here, we report that the fucose salvage pathway inhibits invadopodia formation and extracellular matrix degradation by promoting α-1,2 fucosylation. Chemically or genetically increasing the fucose salvage pathway decreases invadopodium numbers and inhibits the proteolytic activity of invadopodia in WM793 melanoma cells. Inhibiting fucosylation by depleting fucokinase abrogates L-fucose-mediated inhibition of invadopodia, suggesting dependence on the fucose salvage pathway. The inhibition of invadopodium formation by L-fucose or ectopically expressed FUK could be rescued by treatment with α-1,2, but not α-1,3/α-1,4 fucosidase, implicating an α-1,2 fucose linkage-dependent anti-metastatic effect. The expression of FUT1, an α-1,2 fucosyltransferase, is remarkably down-regulated during melanoma progression, and the ectopic expression of FUT1 is sufficient to inhibit invadopodium formation and ECM degradation. Our findings indicate that the fucose salvage pathway can inhibit invadopodium formation, and consequently, invasiveness in melanoma via α-1,2 fucosylation. Re-activation of this pathway in melanoma could be useful for preventing melanoma invasion and metastasis.

A key role for Fut1-regulated angiogenesis and ICAM-1 expression in K/BxN arthritis

OBJECTIVES

Angiogenesis contributes to the pathogenesis of rheumatoid arthritis. Fucosyltransferases (Futs) are involved in angiogenesis and tumour growth. Here, we examined the role of Fut1 in angiogenesis and K/BxN serum transfer arthritis.

METHODS

We examined Fut1 expression in human dermal microvascular endothelial cells (HMVECs) by quantitative PCR. We performed a number of angiogenesis assays to determine the role of Fut1 using HMVECs, Fut1 null (Fut1(-/-)), and wild type (wt) endothelial cells (ECs) and mice. K/BxN serum transfer arthritis was performed to determine the contribution of Fut1-mediated angiogenesis in Fut1(-/-) and wt mice. A static adhesion assay was implemented with RAW264.7 (mouse macrophage cell line) and mouse ECs. Quantitative PCR, immunofluorescence and flow cytometry were performed with Fut1(-/-) and wt ECs for adhesion molecule expression.

RESULTS

Tumour necrosis factor-α induced Fut1 mRNA and protein expression in HMVECs. HMVECs transfected with Fut1 antisense oligodeoxynucleotide and Fut1(-/-) ECs formed significantly fewer tubes on Matrigel. Fut1(-/-) mice had reduced angiogenesis in Matrigel plug and sponge granuloma angiogenesis assays compared with wt mice. Fut1(-/-) mice were resistant to K/BxN serum transfer arthritis and had decreased angiogenesis and leucocyte ingress into inflamed joints. Adhesion of RAW264.7 cells to wt mouse ECs was significantly reduced when Fut1 was lacking. Fut1(-/-) ECs had decreased intercellular adhesion molecule-1 (ICAM-1) expression at mRNA and protein levels compared with wt ECs. ICAM-1 was also decreased in Fut1(-/-) arthritic ankle cryosections compared with wt ankles.

CONCLUSIONS

Fut1 plays an important role in regulating angiogenesis and ICAM-1 expression in inflammatory arthritis.

Mice lacking α1,3-fucosyltransferase 9 exhibit modulation of in vivo immune responses against pathogens

Carbohydrate structures, including Lewis X (Le^x), which is not synthesized in mutant mice that lack α1,3‐fucosyltransferase 9 (Fut9^−/−), are involved in cell–cell recognition and inflammation. However, immunological alteration in Fut9^−/− mice has not been studied. Thus, the inflammatory response of Fut9^−/− mice was examined using the highly neurovirulent mouse hepatitis virus (MHV) JHMV srr7 strain. Pathological study revealed that inflammation induced in the brains of Fut9^−/− mice after infection was more extensive compared with that of wild‐type mice, although viral titers obtained from the brains of mutant mice were lower than those of wild‐type mice. Furthermore, the reduction in cell numbers in the spleens of wild‐type mice after infection was not observed in the infected Fut9^−/− mice. Although there were no clear differences in the levels of cytokines examined in the brains between Fut9^−/− and wild‐type mice except for interferon‐β (IFN‐β) expression, some of those in the spleens, including interferon‐γ (IFN‐γ), interleukin‐6 (IL‐6), and monocyte chemoattractant protein‐1 (MCP‐1), showed higher levels in Fut9^−/− than in wild‐type mice. Furthermore, Fut9^−/− mice were refractory to the in vivo inoculation of endotoxin (LPS) compared with wild‐type mice. These results indicate that Le^x structures are involved in host responses against viral or bacterial challenges.

A novel role for inducible Fut2 in angiogenesis

RATIONALE

Angiogenesis plays an important role in wound healing and tumor growth. Fucosyltransferases synthesize fucosylated glycans and may play a major role in vascular biology.

OBJECTIVE

To examine the role of an alpha(1,2) fucosyltransferase (Fut2) in angiogenesis.

METHODS AND RESULTS

We found that Fut2 mRNA and protein expression is inducible in human dermal microvascular endothelial cells (HMVECs). After finding that Fut2 is inducible in HMVECs, we examined if Fut2 contributes to angiogenesis. We found that Fut2 null endothelial cell (EC) migration and tube formation were significantly less compared to wild type (wt) ECs. Angiogenesis was impaired in Fut2 null compared to wt mice in the mouse Matrigel plug and the sponge granuloma angiogenesis assays. To assess the characteristics of Fut2 null ECs in vivo, we performed Matrigel plug angiogenesis assays in wt mice using Fut2 null and wt mouse ECs. We found a significant decrease in Fut2 null EC incorporation in neoangiogenesis compared to wt ECs. ERK1/2 activation, fibroblast growth factor receptor2, and vascular endothelial growth factor expression were less in Fut2 null ECs, suggesting a possible mechanism of impaired angiogenesis when Fut2 is lacking.

CONCLUSIONS

These data suggest a novel role for Fut2 as a regulator of angiogenesis.

Notch signaling regulates late-stage epidermal differentiation and maintains postnatal hair cycle homeostasis

BACKGROUND

Notch signaling involves ligand-receptor interactions through direct cell-cell contact. Multiple Notch receptors and ligands are expressed in the epidermis and hair follicles during embryonic development and the adult stage. Although Notch signaling plays an important role in regulating differentiation of the epidermis and hair follicles, it remains unclear how Notch signaling participates in late-stage epidermal differentiation and postnatal hair cycle homeostasis.

METHODOLOGY AND PRINCIPAL FINDINGS

We applied Cre/loxP system to generate conditional gene targeted mice that allow inactivation of critical components of Notch signaling pathway in the skin. Rbpj, the core component of all four Notch receptors, and Pofut1, an essential factor for ligand-receptor interactions, were inactivated in hair follicle lineages and suprabasal layer of the epidermis using the Tgfb3-Cre mouse line. Rbpj conditional inactivation resulted in granular parakeratosis and reactive epidermal hyperplasia. Pofut1 conditional inactivation led to ultrastructural abnormalities in the granular layer and altered filaggrin processing in the epidermis, suggesting a perturbation of the granular layer differentiation. Disruption of Pofut1 in hair follicle lineages resulted in aberrant telogen morphology, a decrease of bulge stem cell markers, and a concomitant increase of K14-positive keratinocytes in the isthmus of mutant hair follicles. Pofut1-deficent hair follicles displayed a delay in anagen re-entry and dysregulation of proliferation and apoptosis during the hair cycle transition. Moreover, increased DNA double stand breaks were detected in Pofut1-deficent hair follicles, and real time PCR analyses on bulge keratinocytes isolated by FACS revealed an induction of DNA damage response and a paucity of DNA repair machinery in mutant bulge keratinocytes.

SIGNIFICANCE

our data reveal a role for Notch signaling in regulating late-stage epidermal differentiation. Notch signaling is required for postnatal hair cycle homeostasis by maintaining proper proliferation and differentiation of hair follicle stem cells.

Generation of glyco-engineered BY2 cell lines with decreased expression of plant-specific glycoepitopes

Plants are known to be efficient hosts for the production of mammalian therapeutic proteins. However, plants produce complex N-glycans bearing β1,2-xylose and core α1,3-fucose residues, which are absent in mammals. The immunogenicity and allergenicity of plant-specific Nglycans is a key concern in mammalian therapy. In this study, we amplified the sequences of 2 plant-specific glycosyltransferases from Nicotiana tabacum L. cv Bright Yellow 2 (BY2), which is a well-established cell line widely used for the expression of therapeutic proteins. The expression of the endogenous xylosyltranferase (XylT) and fucosyltransferase (FucT) was downregulated by using RNA interference (RNAi) strategy. The xylosylated and core fucosylated N-glycans were significantly, but not completely, reduced in the glycoengineered lines. However, these RNAi-treated cell lines were stable and viable and did not exhibit any obvious phenotype. Therefore, this study may provide an effective and promising strategy to produce recombinant glycoproteins in BY2 cells with humanized N-glycoforms to avoid potential immunogenicity.

Cervical mucins carry alpha(1,2)fucosylated glycans that partly protect from experimental vaginal candidiasis

Cervical mucins are glycosylated proteins that form a protective cervical mucus. To understand the role of mucin glycans in Candida albicans infection, oligosaccharides from mouse cervical mucins were analyzed by liquid chromatography-mass spectrometry. Cervical mucins carry multiple alpha(1-2)fucosylated glycans, but alpha(1,2)fucosyltransferase Fut2-null mice are devoid of these epitopes. Epithelial cells in vaginal lavages from Fut2-null mice lacked Ulex europaeus agglutinin-1 (UEA-I) staining for alpha(1-2)fucosylated glycans. Hysterectomy to remove cervical mucus eliminated UEA-I and acid mucin staining in vaginal epithelial cells from wild type mice indicating the cervix as the source of UEA-I positive epithelial cells. To assess binding of alpha(1-2) fucosylated glycans on C. albicans infection, an in vitro adhesion assay was performed with vaginal epithelial cells from wild type and Fut2-null mice. Vaginal epithelial cells from Fut2-null mice were found to bind increased numbers of C. albicans compared to vaginal epithelial cells obtained from wild type mice. Hysterectomy lessened the difference between Fut2-null and wild type mice in binding of C. ablicans in vitro and susceptibility to experimental C. albicans vaginitis in vivo. We generated a recombinant fucosylated MUC1 glycanpolymer to test whether the relative protection of wild type mice compared to Fut2-null mice could be mimicked with exogenous mucin. While a small portion of the recombinant MUC1 epitopes displayed alpha(1-2)fucosylated glycans, the predominant epitopes were sialylated due to endogenous sialyltransferases in the cultured cells. Intravaginal instillation of recombinant MUC1 glycanpolymer partially reduced experimental yeast vaginitis suggesting that a large glycanpolymer, with different glycan epitopes, may affect fungal burden.

Loss of core fucosylation of low-density lipoprotein receptor-related protein-1 impairs its function, leading to the upregulation of serum levels of insulin-like growth factor-binding protein 3 in Fut8-/- mice

alpha1,6-Fucosyltransferase (Fut8) catalyzes the transfer of a fucose residue from GDP-fucose to the innermost N-acetylglucosamine residue of N-glycans. Here we report that the loss of core fucosylation impairs the function of low-density lipoprotein (LDL) receptor-related protein-1 (LRP-1), a multifunctional scavenger and signaling receptor, resulting in a reduction in the endocytosis of insulin like growth factor (IGF)-binding protein-3 (IGFBP-3) in the cells derived from Fut8-null (Fut8-/-) mice. The reduced endocytosis was restored by the re-introduction of Fut8. Serum levels of IGFBP-3 were markedly upregulated in Fut8-/- mice. These data clearly indicate that core fucosylation is crucial for the scavenging activity of LRP-1 in vivo.

Phenotype changes of Fut8 knockout mouse: core fucosylation is crucial for the function of growth factor receptor(s)

Alpha1,6-fucosyltransferase (Fut8) catalyzes the transfer of a fucose residue to N-linked oligosaccharides on glycoproteins by means of an alpha1,6-linkage to form core fucosylation in mammals. In mice, disruption of Fut8 induces severe growth retardation, early death during postnatal development, and emphysema-like changes in the lung. A marked dysregulation of TGF-beta1 receptor activation and signaling in Fut8-null mice lung results in overexpression of matrix metalloproteinases (MMPs), such as MMP12 and MMP13, and a down-regulation of extracellular matrix (ECM) proteins such as elastin, which contributes to the destructive emphysema-like phenotype observed in Fut8-null mice. Furthermore, therapeutic administration of exogenous TGF-beta1 rescued the null mice from the emphysema-like phenotype. On the other hand, absence of Fut8 on EGF or PDGF receptor results in down-regulation of the receptor-mediated signaling, which is a plausible factor that may be responsible for the growth retardation. Reintroduction of the Fut8 gene to Fut8-null cells potentially rescued these receptor-mediated signaling impaired in null cells. Collectively, these results suggest that core fucosylation is crucial for growth factor receptors such as TGF-beta1 and EGF receptor-mediated biological functions.

The threonine that carries fucose, but not fucose, is required for Cripto to facilitate Nodal signaling

Cripto is a membrane-bound co-receptor for Nodal, a member of the transforming growth factor-beta superfamily. Mouse embryos lacking either Cripto or Nodal have the same lethal phenotype at embryonic day 7.5. Previous studies suggest that O-fucosylation of the epidermal growth factor-like (EGF) repeat in Cripto is essential for the facilitation of Nodal signaling. Substitution of Ala for the Thr to which O-fucose is attached led to functional inactivation of both human and mouse Cripto. However, embryos null for protein O-fucosyltransferase 1, the enzyme that adds O-fucose to EGF repeats, do not exhibit a Cripto null phenotype and die at about embryonic day 9.5. This suggested that the loss of O-fucose from the EGF repeat may not have led to the inactivation of Cripto in previous studies. Here we investigate this hypothesis and show the following: 1) protein O-fucosyltransferase 1 is indeed the enzyme that adds O-fucose to Cripto; 2) Pofut1(-/-) embryonic stem cells behave the same as Pofut1(+/+) embryonic stem cells in a Nodal signaling assay; 3) Pofut1(-/-) and Pofut1(+/+) embryoid bodies are indistinguishable in their ability to differentiate into cardiomyocytes; and 4) none of 10 amino acid substitutions at Thr(72), including Ser which acquires O-fucose, rescues the activity of mouse Cripto in Nodal signaling assays. Therefore, the Thr to which O-fucose is linked in Cripto plays a key functional role, but O-fucose at Thr(72) is not required for Cripto to function in cell-based signaling assays or in vivo. By contrast, we show that O-fucose, and not the Thr to which it is attached, is required in the ligand-binding domain of Notch1 for Notch1 signaling.

Carbohydrate binding specificity of a fucose-specific lectin from Aspergillus oryzae: a novel probe for core fucose

The alpha1,6-fucosyl residue (core fucose) of glycoproteins is widely distributed in mammalian tissues and is altered under pathological conditions. A probe that specifically detects core fucose is important for understanding the role of this oligosaccharide structure. Aleuria aurantia lectin (AAL) and Lens culimaris agglutinin-A (LCA) have been often used as carbohydrate probes for core fucose in glycoproteins. Here we show, by using surface plasmon resonance (SPR) analysis, that Aspergillus oryzae l-fucose-specific lectin (AOL) has strongest preference for the alpha1,6-fucosylated chain among alpha1,2-, alpha1,3-, alpha1,4-, and alpha1,6-fucosylated pyridylaminated (PA)-sugar chains. These results suggest that AOL is a novel probe for detecting core fucose in glycoproteins on the surface of animal cells. A comparison of the carbohydrate-binding specificity of AOL, AAL, and LCA by SPR showed that the irreversible binding of AOL to the alpha1,2-fucosylated PA-sugar chain (H antigen) relative to the alpha1,6-fucosylated chain was weaker than that of AAL, and that the interactions of AOL and AAL with alpha1,6-fucosylated glycopeptide (FGP), which is considered more similar to in vivo glycoproteins than PA-sugar chains, were similar to their interactions with the alpha1,6-fucosylated PA-sugar chain. Furthermore, positive staining of AOL, but not AAL, was completely abolished in the cultured embryo fibroblast (MEF) cells obtained from alpha1,6-fucosyltransferase (Fut8) knock-out mice, as assessed by cytological staining. Taken together, these results suggest that AOL is more suitable for detecting core fucose than AAL or LCA.

Significant decrease in alpha1,3-linked fucose in association with increase in 6-sulfated N-acetylglucosamine in peripheral lymph node addressin of FucT-VII-deficient mice exhibiting diminished lymphocyte homing

Lymphocyte homing is mediated by binding of L-selectin on lymphocytes with L-selectin ligands present on high-endothelial venules (HEV) of peripheral and mesenteric lymph nodes. L-selectin ligands are specific O-linked carbohydrates, 6-sulfo sialyl Lewis X, composed of sialylated, fucosylated, and sulfated glycans. Abrogation of fucosyltransferase-VII (FucT-VII) results in almost complete loss of lymphocyte homing, but structural analysis of carbohydrates has not been carried out on FucT-VII null mice. To determine whether functional losses seen in FucT-VII null mice are caused by structural changes in carbohydrates, we elucidated the carbohydrate structure of GlyCAM-1, a major L-selectin counter-receptor. Our results show that most alpha1,3-fucosylated structures in 6-sulfo sialyl Lewis X are absent and 6-sulfo N-acetyllactosamine is increased in the mutant mice. Surprisingly, the amount of 6'-sulfated galactose (Gal) that bound to Sumbucus nigra agglutinin column was also increased. We found that structures of those oligosaccharides containing 6'-sulfated Gal are almost identical to those synthesized by keratan sulfate sulfotransferase (KSST). We then showed that overexpression of KSST suppresses the expression of sialyl Lewis X on Chinese hamster ovary (CHO) cells engineered to express sialyl Lewis X. Moreover, KSST expression in those cells suppressed lymphocyte rolling compared with mock-transfected CHO cells expressing 6-sulfo sialyl Lewis X. 6'-Sulfo sialyl Lewis X can neither be found in GlyCAM-1 from CHO cells expressing both KSST and FucT-VII nor be found in GlyCAM-1 from HEV of mice. These results combined together suggest that KSST competes with FucT-VII for the same acceptor substrate and downregulates the synthesis of L-selectin ligand by inhibiting alpha1,3-fucosylation.

Generation of soluble P- and E-selectins in vivo is dependent on expression of P-selectin glycoprotein ligand-1

BACKGROUND

Factors contributing to the generation of soluble P- and E-selectins remain unclear.

RESULTS

This work demonstrates that mice lacking P-selectin glycoprotein ligand-1 (Psgl-1(-/-)) are deficient in soluble P-selectin (sP-sel), which is due to a defective binding interaction between PSGL-1 and P-sel, because mice lacking alpha(1,3)-fucosyltransferase-VII are also deficient in sP-sel. Psgl-1(-/-) mice are also deficient in soluble E-selectin (sE-sel) indicating that leukocyte interactions with endothelial cells lead to the generation of sE-sel. The generation of sE-sel requires an interaction between PSGL-1 and P-sel, as deficiency of sE-sel is observed in both Psgl-1(-/-) and P-sel(-/-) mice. Bone marrow transplantation from Psgl-1(-/-) to Psgl-1(+/+) mice leads to deficiency of sP-sel and sE-sel in recipient mice, establishing the importance of bone marrow-derived PSGL-1 toward the generation of sP-sel and sE-sel. Bone marrow transplantation from P-sel(-/-) to P-sel1(+/+) mice does not lead to a significant reduction in sP-sel, confirming the importance of the endothelium toward the liberation of sP-sel.

CONCLUSION

sP-sel and sE-sel reflect an interaction between leukocyte PSGL-1 and endothelial P-sel.

Crystal structure of mammalian α1,6-fucosyltransferase, FUT8

Mammalian alpha1,6-fucosyltransferase (FUT8) catalyses the transfer of a fucose residue from a donor substrate, guanosine 5'-diphosphate-beta-L-fucose to the reducing terminal N-acetylglucosamine (GlcNAc) of the core structure of an asparagine-linked oligosaccharide. Alpha1,6-fucosylation, also referred to as core fucosylation, plays an essential role in various pathophysiological events. Our group reported that FUT8 null mice showed severe growth retardation and emphysema-like lung-destruction as a result of the dysfunction of epidermal growth factor and transforming growth factor-beta receptors. To elucidate the molecular basis of FUT8 with respect to pathophysiology, the crystal structure of human FUT8 was determined at 2.6 A resolution. The overall structure of FUT8 was found to consist of three domains: an N-terminal coiled-coil domain, a catalytic domain, and a C-terminal SH3 domain. The catalytic region appears to be similar to GT-B glycosyltransferases rather than GT-A. The C-terminal part of the catalytic domain of FUT8 includes a Rossmann fold with three regions that are conserved in alpha1,6-, alpha1,2-, and protein O-fucosyltransferases. The SH3 domain of FUT8 is similar to other SH3 domain-containing proteins, although the significance of this domain remains to be elucidated. The present findings of FUT8 suggest that the conserved residues in the three conserved regions participate in the Rossmann fold and act as the donor binding site, or in catalysis, thus playing key roles in the fucose-transferring reaction.

Fucosylation of N-glycans regulates the secretion of hepatic glycoproteins into bile ducts

Fucosylated alpha-fetoprotein (AFP) is a highly specific tumor marker for hepatocellular carcinoma (HCC). However, the molecular mechanism by which serum level of fucosylated AFP increases in patients with HCC remains largely unknown. Here, we report that the fucosylation of glycoproteins could be a possible signal for secretion into bile ducts in the liver. We compared oligosaccharide structures on glycoproteins in human bile with those in serum by several types of lectin blot analyses. Enhanced binding of biliary glycoproteins to lectins that recognize a fucose residue was observed over a wide range of molecular weights compared with serum glycoproteins. A structural analysis of oligosaccharides by two-dimensional mapping high performance liquid chromatography and matrix-assisted laser desorption ionization time-of flight mass spectrometry confirmed the increases in the fucosylation of biliary glycoproteins. Purification followed by structural analysis on alpha1-antitrypsin, alpha1-acid glycoprotein and haptoglobin, which are synthesized in the liver, showed higher fucosylation in bile than in serum. To find direct evidence for fucosylation and sorting signal into bile ducts, we used alpha1-6 fucosyltransferase (Fut8)-deficient mice because fucosylation of glycoproteins produced in mouse liver was mainly an alpha1-6 linkage. Interestingly, the levels of alpha1-antitrypsin and alpha1-acid glycoprotein were quite low in bile of Fut8-deficient mice as compared with wild-type mice. An immunohistochemical study showed dramatic changes in the localization of these glycoproteins in the liver of Fut8-deficient mice. Taken together, these results suggest that fucosylation is a possible signal for the secretion of glycoproteins into bile ducts in the liver. A disruption in this system might involve an increase in fucosylated AFP in the serum of patients with HCC.

Abrogation of Functional Selectin-Ligand Expression Reduces Migration of Pathogenic CD8+T Cells into Heart

CD8+ T cells are involved in autoimmune and infectious myocarditis and cardiac allograft rejection. The role of selectins in cardiac recruitment of CD8+ T cells is not understood. In this study, the contribution of T cell selectin ligands to effector CD8+ T cell recruitment into the heart was examined using a model of myocarditis, which depends on transfer of OVA peptide-specific CD8+ T cells (OT-I) into mice (CMy-mOva) that express OVA in the heart. alpha-(1,3)-Fucosyltransferase (FucT)-VII-deficient OT-I cells displayed over a 95% reduction in their ability to interact with P-selectin under flow conditions in vitro, compared with wild-type OT-I cells. Interaction of FucT-VII-deficient OT-I cells with E-selectin was reduced approximately 50%. FucT-VII-deficient OT-I cells were also less efficiently recruited into a dermal site of Ag and adjuvant injection. Significantly, FucT-VII-deficient OT-I cells were also impaired in their ability to migrate into CMy-mOva hearts, compared with wild-type OT-I cells. Transfer of FucT-VII-deficient T cells caused less severe early myocarditis and myocyte damage than transfer of wild-type T cells. Combined FucT-IV/VII-deficient OT-I cells displayed a more profound reduction in E-selectin interactions in vitro compared with FucT-VII-deficient T cells, and the FucT-IV/VII-deficient T cells also showed less early recruitment and pathogenicity in the CMy-mOva myocarditis model. These results identify a prominent role for selectin ligands in contributing to effector CD8+ T cell recruitment into the myocardium and indicate that selectin-dependent T cell recruitment is relevant to other tissues besides the skin.

L-Selectin Facilitation of Metastasis Involves Temporal Induction of Fut7-Dependent Ligands at Sites of Tumor Cell Arrest

Hematogenous carcinoma metastasis is supported by aggregated platelets and leukocytes, forming tumor cell emboli. Early tumor cell-platelet interactions can be mediated by P-selectin binding to tumor cell surface ligands and this process is blocked by heparin. We previously showed that L-selectin deficiency also attenuates experimental metastasis. However, the mechanisms and timing of L-selectin action remained unknown. Here, we study how L-selectin facilitates establishment of pulmonary metastatic foci in syngeneic mice by using experimental metastasis to time events following entry of tumor cells into the bloodstream. Although L-selectin deficiency did not affect platelet aggregation or initial tumor cell embolization, the association of leukocytes with tumor cells was reduced and tumor cell survival was diminished 24 hours later. Temporal inhibition of L-selectin by a function-blocking antibody reduced metastasis. Moreover, although selectin blockade by heparin 6 to 18 hours after tumor cell injection was synergistic with P-selectin deficiency in reducing metastasis, there was no further effect in L-selectin-deficient animals. Thus, heparin apparently works at these time points primarily by blocking L-selectin. Endogenous L-selectin ligands were concomitantly induced adjacent to established intravascular tumor cell emboli in a similar time window when leukocytes were also present. Metastasis was attenuated in mice missing these induced endogenous L-selectin ligands due to fucosyltransferase-7 deficiency. Thus, L-selectin facilitation of metastasis progression involves leukocyte-endothelial interactions at sites of intravascular arrest supported by local induction of L-selectin ligands via fucosyltransferase-7. These data provide the first explanation for how leukocyte L-selectin facilitates tumor metastasis.

Selectin Ligand-Independent Priming and Maintenance of T Cell Immunity during Airborne Tuberculosis

Immunity to Mycobacterium tuberculosis infection is critically dependent on the timely priming of T effector lymphocytes and their efficient recruitment to the site of mycobacterial implantation in the lung. E-, P-, and L-selectin counterreceptors control lymphocyte homing to lymph nodes and leukocyte trafficking to peripheral sites of acute inflammation, their adhesive function depending on fucosylation by fucosyltransferases (FucT) IV and VII. To address the relative importance of differentially glycosylated selectin counterreceptors for priming of T cell effector functions in a model of mycobacteria-induced granulomatous pulmonary inflammation, we used aerosol-borne M. tuberculosis to infect FucT-IV-/-, FucT-VII-/-, FucT-IV-/-/FucT-VII-/-, or wild-type control mice. In lymph nodes, infected FucT-IV-/-/FucT-VII-/- and, to a lesser extent, FucT-VII-/- mice had severely reduced numbers of T cells and reduced Ag-specific effector responses. By contrast, recruitment of activated T cells into the lungs was similar in all four groups of mice during infection and expression of T cell, and macrophage effector functions were only delayed in lungs of FucT-IV-/-/FucT-VII-/- mice. Importantly, lungs from all groups expressed CXCL13, CCL21, and CCL19 and displayed organized follicular neolymphoid structures after infection with M. tuberculosis, which suggests that the lung served as a selectin ligand-independent priming site for immune responses to mycobacterial infection. All FucT-deficient strains were fully capable of restricting M. tuberculosis growth in infected organs until at least 150 days postinfection. Our observations indicate that leukocyte recruitment functions dictated by FucT-IV and FucT-VII-dependent selectin ligand activities are not critical for inducing or maintaining T cell effector responses at levels necessary to control pulmonary tuberculosis.

T-cell P/E-selectin ligand α(1,3)fucosylation is not required for graft-vs-host disease induction

OBJECTIVE

Recognition of E- and P-selectins on vascular endothelium by their leukocyte glycoprotein counterreceptor P-selectin glycoprotein ligand-1 (PSGL-1) initiates and sustains leukocyte rolling, culminating in extravasation of lymphocytes from blood into organs. PSGL-1 is rendered functional by terminal glycosylation steps, which occur mainly in activated Th1 but not Th2 cells. alpha(1,3)Fucosyltransferases IV and VII control this glycosylation pathway. Mice lacking these transferases (Fuc-TIV(-/-)/Fuc-TVII(-/-)) lack functional E- and P-selectin ligands. We hypothesized that Fuc-TIV(-/-)/Fuc-TVII(-/-) donor T cells might have reduced capacity to roll on vessels of inflamed target tissues and mediate graft-vs-host disease (GVHD).

MATERIALS AND METHODS

We compared the ability of Fuc-TIV(-/-)/Fuc-TVII(-/-) and wild-type (WT) C57BL/6 (B6) spleen cells (SPCs) to produce GVHD in lethally irradiated major histocompatibility complex (MHC) haplotype-mismatched B6D2F1 recipients. Clinical GVHD, GVHD pathology in target organs, memory phenotype conversion, proliferation of donor T cells, and tissue and serum cytokine expression were examined.

RESULTS

Surprisingly, clinical GVHD was not reduced in lethally irradiated mice receiving full haplotype MHC mismatched or matched Fuc-TIV(-/-)/Fuc-TVII(-/-) SPCs compared to those receiving WT SPCs. GVHD pathology in target organs, memory phenotype conversion, and proliferation of donor T cells were similar in both groups. However, reduced interferon-gamma was detected in liver and lung, and serum levels of tumor necrosis factor-alpha were higher in mice receiving Fuc-TIV(-/-)/Fuc-TVII(-/-) SPCs compared with WT SPCs.

CONCLUSIONS

These results suggest that donor T cells, including Th1, are capable of trafficking to GVHD target tissues independently of P- and E- selectin ligand in conditioned hosts.

Dysregulation of TGF-beta1 receptor activation leads to abnormal lung development and emphysema-like phenotype in core fucose-deficient mice

The core fucosylation (alpha1,6-fucosylation) of glycoproteins is widely distributed in mammalian tissues, and is altered under pathological conditions. To investigate physiological functions of the core fucose, we generated alpha1,6-fucosyltransferase (Fut8)-null mice and found that disruption of Fut8 induces severe growth retardation and death during postnatal development. Histopathological analysis revealed that Fut8(-/-) mice showed emphysema-like changes in the lung, verified by a physiological compliance analysis. Biochemical studies indicated that lungs from Fut8(-/-) mice exhibit a marked overexpression of matrix metalloproteinases (MMPs), such as MMP-12 and MMP-13, highly associated with lung-destructive phenotypes, and a down-regulation of extracellular matrix (ECM) proteins such as elastin, as well as retarded alveolar epithelia cell differentiation. These changes should be consistent with a deficiency in TGF-beta1 signaling, a pleiotropic factor that controls ECM homeostasis by down-regulating MMP expression and inducing ECM protein components. In fact, Fut8(-/-) mice have a marked dysregulation of TGF-beta1 receptor activation and signaling, as assessed by TGF-beta1 binding assays and Smad2 phosphorylation analysis. We also show that these TGF-beta1 receptor defects found in Fut8(-/-) cells can be rescued by reintroducing Fut8 into Fut8(-/-) cells. Furthermore, exogenous TGF-beta1 potentially rescued emphysema-like phenotype and concomitantly reduced MMP expression in Fut8(-/-) lung. We propose that the lack of core fucosylation of TGF-beta1 receptors is crucial for a developmental and progressive/destructive emphysema, suggesting that perturbation of this function could underlie certain cases of human emphysema.

Efficient Recruitment of Lymphocytes in Inflamed Brain Venules Requires Expression of Cutaneous Lymphocyte Antigen and Fucosyltransferase-VII

Lymphocyte migration into the brain represents a critical event in the pathogenesis of multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). However, the mechanisms controlling the recruitment of lymphocytes to the CNS via inflamed brain venules are poorly understood, and therapeutic approaches to inhibit this process are consequently few. In this study, we demonstrate for the first time that human and murine Th1 lymphocytes preferentially adhere to murine inflamed brain venules in an experimental model that mimics early inflammation during EAE. A virtually complete inhibition of rolling and arrest of Th1 cells in inflamed brain venules was observed with a blocking anti-P-selectin glycoprotein ligand 1 Ab and anti-E- and P-selectin Abs. Th1 lymphocytes produced from fucosyltransferase (FucT)-IV(-/-) mice efficiently tethered and rolled, whereas in contrast, primary adhesion of Th1 lymphocytes obtained from FucT-VII(-/-) or Fuc-VII(-/-)FucT-IV(-/-) mice was drastically reduced, indicating that FucT-VII is critical for the recruitment of Th1 cells in inflamed brain microcirculation. Importantly, we show that Abs directed against cutaneous lymphocyte Ag (CLA), a FucT-VII-dependent carbohydrate modification of P-selectin glycoprotein ligand 1, blocked rolling of Th1 cells. By exploiting a system that allowed us to obtain Th1 and Th2 cells with skin- vs gut-homing (CLA(+) vs integrin beta(7)(+)) phenotypes, we observed that induced expression of CLA on Th cells determined a striking increase of rolling efficiency in inflamed brain venules. These observations allow us to conclude that efficient recruitment of activated lymphocytes to the brain in the contexts mimicking EAE is controlled by FucT-VII and its cognate cell surface Ag CLA.

Increased susceptibility of secretor factor gene Fut2-null mice to experimental vaginal candidiasis

Fut2-LacZ-null mice, which are a model of the human ABO and Lewis nonsecretor group, display increased susceptibility to experimental yeast vaginitis, indicating a role for alpha(1,2)fucosylated cervical glycans in mucosal defense. However, the lack of significant effect of competitive inhibition by exogenous neoglycoproteins in this study emphasizes the complexity of Candida-epithelial cell adhesion events.

Normal embryonic and germ cell development in mice lacking alpha 1,3-fucosyltransferase IX (Fut9) which show disappearance of stage-specific embryonic antigen 1

Stage-specific embryonic antigen 1 (SSEA-1), an antigenic epitope defined as a Lewis x carbohydrate structure, is expressed during the 8-cell to blastocyst stages in mouse embryos and in primordial germ cells, undifferentiated embryonic stem cells, and embryonic carcinoma cells. For many years, SSEA-1 has been implicated in the development of mouse embryos as a functional carbohydrate epitope in cell-to-cell interaction during morula compaction. In a previous study, alpha 1,3-fucosyltransferase IX (Fut9) exhibited very strong activity for the synthesis of Lewis x compared to other alpha 1,3-fucosyltransferases in an in vitro substrate specificity assay. Fut4 and Fut9 transcripts were expressed in mouse embryos. The Fut9 transcript was detected in embryonic-day-13.5 gonads containing primordial germ cells, but the Fut4 transcript was not. In order to identify the role of SSEA-1 and determine the key enzyme for SSEA-1 synthesis in vivo, we have generated Fut9-deficient (Fut9(-/-)) mice. Fut9(-/-) mice develop normally, with no gross phenotypic abnormalities, and are fertile. Immunohistochemical analysis revealed an absence of SSEA-1 expression in early embryos and primordial germ cells of Fut9(-/-) mice. Therefore, we conclude that expression of the SSEA-1 epitope in the developing mouse embryo is not essential for embryogenesis in vivo.

Tissue-specific loss of fucosylated glycolipids in mice with targeted deletion of alpha(1,2)fucosyltransferase genes

Glycolipids in epithelial tissues of the gastrointestinal tract act as receptors for enteric bacteria and are implicated in the activation of the intestinal immune system. To clarify the genes involved in the fucosylation of the major glycolipids, substrate glycolipids and fucosylated products were measured in tissues of wild-type and mutant mice lacking alpha(1,2)fucosyltransferase genes FUT1 or FUT2. Quantitative determination was performed by TLC-immunostaining for GA1 (Gg4Cer), FGA1 (fucosyl GA1), GM1 (II3NeuAc-Gg4Cer), FGM1 (fucosyl GM1), and Forssman glycolipids. Both FGM1 and FGA1 completely disappeared from the antrum, cecum, and colon of FUT2-null mice, but not those of FUT1-null and wild-type mice. Precursor glycolipids, GM1 and GA1, accumulated in tissues of FUT2-null mice, indicating that the FUT2-encoded enzyme preferentially participates in the fucosylation of GA1 and GM1 in these tissues. Female reproductive organs were similarly found to utilize FUT2 for the fucosylation of glycolipids FGA1 (uterus and cervix), and FGM1 (ovary), due to their absence in FUT2-null mice. In FUT1-null mice FGA1 was lost from the pancreas, but was present in wild-type and FUT2-null mice, indicating that FUT1 is essential for fucosylation of GA1 in the pancreas. Ulex europaeus agglutinin-I lectin histochemistry for alpha(1,2)fucose residues confirmed the absence of alpha(1,2)fucose residues from the apical surface of pancreatic acinar glands of FUT1-null mice. Ileum, epididymis, and testis retained specific fucosylated glycolipids, irrespective of targeted deletion of either gene, indicating either compensation for or redundancy of the alpha(1,2)fucosyltransferase genes in these tissues.

Generation of Arabidopsis thaliana plants with complex N-glycans lacking beta1,2-linked xylose and core alpha1,3-linked fucose

The plant glycosyltransferases, beta1,2-xylosyltransferase (XylT) and core alpha1,3-fucosyltransferase (FucT), are responsible for the transfer of beta1,2-linked xylose and core alpha1,3-linked fucose residues to glycoprotein N-glycans. These glycan epitopes are not present in humans and thus may cause immunological responses, which represent a limitation for the therapeutic use of recombinant mammalian glycoproteins produced in transgenic plants. Here we report the genetic modification of the N-glycosylation pathway in Arabidopsis thaliana plants. Knockout plants were generated with complete deficiency of XylT and FucT. These plants lack antigenic protein-bound N-glycans and instead synthesise predominantly structures with two terminal betaN-acetylglucosamine residues (GlcNAc(2)Man(3)GlcNAc(2)).

Two prevalent h alleles in para-Bombay haplotypes among 250,000 Taiwanese

Alpha(1,2)-fucosyltransferase catalyzes the transfer of fucose to the C-2 position of galactose on type II precursor substrate Gal beta1-4GlcNAc beta1-R. It plays an important biological role in the formation of H antigen, a precursor oligosaccharide for both A and B antigens on red blood cells. Aberration of alpha(1,2)-fucosyltransferase activity by gene mutations results in decreased synthesis of H antigen, leading to the para-Bombay phenotype. In this study, we collected about 250,000 blood samples in Taiwan during 5 yr and identified the subjects with para-Bombay phenotype. Then we analyzed the sequence of the alpha(1,2)-fucosyltransferase gene by direct sequencing and gene cloning methods, using the blood samples of 30 para-Bombay individuals and 30 control subjects who were randomly selected. The goals of this study were to search for new h alleles, to determine the h allele frequencies, and to test whether the sporadic theory is applicable in Taiwan. Six different h alleles (ha, 547-548 AG-del; hb, 880-881 TT-del; hc, R220C; hd, R220H; he, F174L; and hf, N327T) were observed. Two h alleles, he and hf, were newly discovered in Taiwan. The he allele has a nucleotide 522C>A point mutation, predicting the amino acid 174 substitution of Phe to Leu; the hf allele has missense mutation of nucleotide 980A>C, predicting the amino acid 327 substitution of Asn to Thr. Frequencies of the 6 alleles are ha 46.67%, hb 38.33%, hc 5.00%, hd 1.67%, he 3.33%, and hf 5.00%, respectively. These findings in the Taiwanese population confirm previous observations in other populations that the Bombay and para-Bombay phenotypes are due to diverse, sporadic, nonfunctional alleles, predominantly ha and hb, leading to H deficiency of red blood cells. In contrast to previous reports of non-prevalent associations of h alleles with para-Bombay phenotype, our results suggest a regional allele preference associated with para-Bombay individuals in Taiwan.

Molecular genetic analysis of para-Bombay phenotypes in Chinese: a novel non-functional FUT1 allele is identified

BACKGROUND AND OBJECTIVES

The para-Bombay phenotype (also known as H-deficient secretor) is characterized by a lack of ABH antigens on red cells, but ABH substances are found in saliva. Molecular genetic analysis was performed for five Chinese individuals serologically typed as para-Bombay.

MATERIALS AND METHODS

ABO genotyping and mutational analysis of both FUT1 (or H) and FUT2 (or Se) loci were performed for these individuals using the polymerase chain reaction, single-strand conformation polymorphism analysis and direct DNA sequencing.

RESULTS

The ABO genotypes of these para-Bombay individuals correlated with the types of ABH substances found in the saliva. Their FUT1 genotypes were h1h2 (three individuals), h2h2 (one individual) and h2h6 (one individual). Alleles h1 (547-552delAG) and h2 (880-882delTT) were known frameshift mutations, while h6 (522C > A) was a missense mutation (Phe174Leu) not previously reported. These three mutations were rare sequence variations, each with an allele frequency of less than 0.005. Phe174 might be functionally important because this residue is conserved from mouse to human. Their FUT2 genotypes were Se357se357,385 for the h2h6 individual and Se357Se357) for the others. Both FUT2 alleles were known: one functional (Se357) and one weakly functional (se357,385). That they carried at least one copy of a functional FUT2 allele was consistent with their secretor status. As FUT1 and FUT2 are adjacent on 19q13.3, there are three possible haplotypes in these para-Bombay individuals: h1-Se357; h2-Se357; and h6-se357,385.

CONCLUSIONS

A novel non-functional FUT1 allele (522C > A, or Phe174Leu) was identified in a para-Bombay individual and on a se357,385 haplotype background.

Pathophysiological contributions of fucosyltransferases in renal ischemia reperfusion injury

Ischemia reperfusion injury (IRI) is a major cause of delayed graft function. Recent studies have shown that selectins play an important role in IRI. Selectins bind to sialylated and fucosylated sLe(x) receptors, and two enzymes, fucosyltransferase IV (FucT-IV) and VII (FucT-VII), are important in the function of these receptors. We hypothesized that fucosyltransferase (FucT) enzymes were important pathophysiologic mediators of renal IRI. We therefore evaluated renal IRI in mice deficient in FucT-IV, FucT-VII, and both FucT-IV and FucT-VII and compared their renal function, tubular injury, selectin ligand expression, and neutrophil infiltration to those in wild-type control mice. Bilateral 30-min renal IRI was performed, and the results demonstrated that mice deficient in both FucT-IV/FucT-VII were significantly protected from renal IRI at 24 and 48 h compared with wild-type control mice. FucT-IV-deficient mice showed only modest protection from renal injury at 24 h. However, FucT-VII-deficient mice had similar injury as wild-type mice. Histological analysis of kidney tissue postischemia revealed that mice deficient in both FucT-IV and FucT-VII had significantly reduced tubular injury compared with wild-type mice. Selectin ligand expression increased postischemia in wild-type, but not FucT-IV/FucT-VII-deficient, mice. Neutrophil infiltration in postischemic kidneys of FucT-IV/FucT-VII-deficient mice was also attenuated. These data demonstrate that fucosyltransferases are important in the pathogenesis of renal IRI and are potential therapeutic targets.

Fuc-TVII is required for T helper 1 and T cytotoxic 1 lymphocyte selectin ligand expression and recruitment in inflammation, and together with Fuc-TIV regulates naive T cell trafficking to lymph nodes

To determine how the alpha(1,3)fucosyltransferases Fuc-TIV and Fuc-TVII, and the selectin ligands they control may contribute to the adaptive immune response, contact hypersensitivity (CHS) was characterized in mice deficient in either or both enzymes. We find a substantial CHS deficiency in Fuc-TVII(-/-) mice, and a complete deficiency in Fuc-TIV(-/-)/Fuc-TVII(-/-) mice. These defects are not accounted for by alterations in the number or function of epidermal Langerhans cells required for cutaneous antigen processing and presentation. By contrast, defective CHS in Fuc-TVII(-/-) mice or Fuc-TIV(-/-)/Fuc-TVII(-/-) mice is attributed in part to prominent, or nearly complete deficiencies, respectively, in the complement of naive T lymphocytes available in lymph nodes for antigen-dependent activation, expansion, differentiation, and dissemination. Fuc-TVII deficiency also deletes expression of E- and P-selectin ligands by Th1 and T cytotoxic 1 (Tc1) lymphocytes, annuls T cell trafficking to inflamed cutaneous sites in vivo, and thereby controls an essential component of the efferent phase of the cutaneous immune response. These observations indicate that collaborative contributions of Fuc-TIV and Fuc-TVII to L-selectin ligand synthesis, and to lymphocyte recruitment, are requisite components of the primary cellular immune response, and assign an essential role to Fuc-TVII in control of E- and P-selectin ligand expression by Th1 and Tc1 lymphocytes.

Molecular analysis of plasma alpha 1,3-fucosyltransferase deficiency and development of the methods for its genotyping

Four patients with mental illness were found to be deficient in plasma alpha1,3-fucosyltransferase for the first time in Japan [Exp Clin Immunogenet 1999;16:125-130]. Complete sequencing of FUT6 genes in these individuals revealed the presence of two point mutations, i.e., G739 to A (Glu-->247 to Lys) and C945 to A (Tyr-->315 to stop). In addition to two reported alleles having G739 to A (pf1) and G739 to A and C945 to A (pf3), a new mutated allele having C945 to A (pf2) was found to be present and all the individuals who lack alpha1,3-fucosyltransferase activity in plasma were found to possess pf genes homozygously (pf/pf). In order to detect such lethal mutations in FUT6 genes easily, PCR-RFLP methods have also been developed and applied for the screening of FUT6 deficiency in a large number of samples which resulted in the demonstration of three additional FUT6-deficient individuals. The absence of alpha1,3-fucosylated molecules on alpha(1)-acid glycoprotein in plasma from all the 7 individuals was confirmed to result from the plasma alpha1,3-fucosyltransferase deficiency.

Identification of two functionally deficient plasma alpha 3-fucosyltransferase (FUT6) alleles

One Indonesian individual without detectable plasma alpha3-fucosyltransferase activity was identified with three point mutations, 730C>G (L244V), 907C>G (R303G), and 370C>T (P124S), in the coding region of one FUT6 allele. Another individual, expressing weak plasma alpha3-fucosyltransferase activity, had the 907C>G together with the 370C>T mutation, but did not have the 730C>G mutation. PCR-RFLP analyses of complete families confirmed the segregation of these alleles and illustrated the existence and inheritance of the [370C>T; 907C>G] mutated allele in three additional families. Altogether, this allele was found heterozygously in nine Indonesian and two Swedish individuals, all with detectable plasma alpha3-fucosyltransferase activities. The FUT6 allele with the three mutations (370C>T; 730C>G; 907C>G) was identified heterozygously in only two Indonesian individuals, both having the inactivating 739G>A mutation in the other allele and both lacking plasma alpha3-fucosyltransferase activity. Enzyme studies made on transiently transfected COS-7 cells demonstrated that the combination of the 370C>T, 730C>G and 907C>G mutations decreased the V(max) by more than 80%, but caused no obvious change of the apparent K(m) values for GDP-fucose and Gal-N-acetyllactosamine. In comparison, chimeric constructs with the isolated 730C>G or 907C>G mutations decreased the V(max) values by about two thirds and one third, respectively.

Synthesis of mono- and di-fucosylated type I Lewis blood group antigens by Helicobacter pylori

The identification of Helicobacter pylori isolates that expresses exclusively type I Lewis antigens is necessary to determine the biosynthetic pathway of these antigens. Fast-atom bombardment MS provides evidence that the H. pylori isolate UA1111 expresses predominantly Leb, with H type I and Lea in lesser amounts. Cloning and expression of the H. pylori fucosyltransferases (FucTs) allow comparisons with previously identified H. pylori enzymes and determination of the enzyme specificities. Although all FucTs, one alpha(1,2) FucT and two alpha(1,3/4) FucTs, appear to be functional in this isolate, their activities are lower and enzyme specificities are different to other H. pylori FucTs previously characterized. Studies of the cloned enzyme activities and mutational analysis indicate that Lea acts as the substrate for the synthesis of Leb. This is different from the human Leb biosynthetic pathway, but analogous to the biosynthetic pathway utilized by H. pylori for the production of Ley.

Mechanisms of NSAID-induced gastrointestinal injury defined using mutant mice

BACKGROUND & AIMS

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used agents that have a high incidence of gastrointestinal side effects resulting in significant morbidity and mortality. Leukocytes have been implicated in NSAID-induced injury, but the mechanisms are unclear. We established a murine model of NSAID-induced gastrointestinal damage to assess the roles of candidate gene products in the pathogenesis of this injury.

METHODS

Indomethacin-induced gastrointestinal injury was assessed in wild-type and several mutant murine lines. Leukocyte involvement was assessed by neutrophil depletion, impairment of recruitment (resulting from targeted disruption of fucosyltransferase VII [FTVII]), and the absence of mature T and B cells with the use of Rag 2(-/-) mice. Activation and oxygen free radicals were assessed using gp91(phox-/-) mice that exhibit normal leukocyte recruitment but are deficient in myeloid cell activation and oxygen free radical generation.

RESULTS

Impairment of leukocyte recruitment (FTVII(/-)) and neutrophil depletion resulted in more than a 50% reduction in NSAID-induced injury. However, mice deficient in mature T and B cells had NSAID-induced damage comparable to control mice. Leukocyte activation was required for NSAID-induced damage because the gp91(phox-/-) mice were less susceptible to NSAID injury than wild-type mice.

CONCLUSIONS

In this murine model system, FTVII-dependent leukocyte recruitment, leukocyte activation via gp91(phox), and neutrophils are required for NSAID-induced gastrointestinal injury, whereas T and B cells are not essential.

Reduced phagocytic activity of polymorphonuclear leukocytes in alpha(1,3) fucosyltransferase VII-deficient mice

Deficiencies in adhesion molecules or their counter-receptors in humans may have severe consequences as exemplified by leukocyte adhesion deficiency (LAD) I or II syndromes. Because such diseases occur with great rarity, animal models are valuable for studying the role of particular adhesion molecules and their natural ligands in immunity. We studied selected immune parameters and general health in mice with a defect in the sialyl-Lewis X antigen (selectin ligand) caused by disruption of the gene encoding alpha(1,3)fucosyltransferase VII (Fuc-TVII). Leukocytes from Fuc-TVII -/- and control mice were tested for adherence to cellophane membranes or polymer particles in vivo and phagocytic activity in vitro. While no difference in adherence was found, the number of neutrophil granulocytes in exudate induced by intraperitoneal injection of polymer beads was reduced in knock-out mice. Moreover, the phagocytic activity in Fuc-TVII -/- mice was significantly reduced. These animals have splenomegaly due to increased hematopoiesis and reduced weight but do not exhibit clinical signs of immunodeficiency. In conclusion, the lack of Fuc-TVII activity leads to several morphological and functional abnormalities without an impact on survival rate.

Molecular genetics of H

BACKGROUND AND OBJECTIVES

Formal genetics of ABO, H-h and Se-se systems illustrate that these three systems are genetically independent

MATERIALS AND METHODS

Population analysis of phenotypes and family segregation of the ABH related genetic markers

RESULTS

Inactivating mutations of FUT1 and FUT2 are compatible with a structural gene model assuming that FUT1 and FUT2 genes encode for two distinct enzymes, one encoding for the H antigen expressed in red cells (FUT1) and the other encoding for the H gene expressed in saliva (FUT2)

CONCLUSION

Most inactivating mutations of FUT1 and FUT2 genes are located in the coding region of the genes and are nonprevalent sporadic mutations of relative recent appearance.

Molecular characterization of secretor type alpha(1, 2)-fucosyltransferase gene deficiency in the Philippine population

We analyzed the seven mutations which are responsible for the deficiency of the secretor type alpha(1,2)-fucosyltransferase gene product, Se enzyme, in the Philippine population. One hundred and one unrelated Filipinos in Taiwan were studied. A new mutation, a 3-base pair deletion from nt 688 through 690, was found in two (0. 1%) of 202 chromosomes. The frequencies of six other mutated alleles were as follows: 71/202 (35.2%) were cDNA 385 A-->T missensed mutation (se2), 28/202 (13.9%) were C571T nonsense mutation (se3), 16/202 (7.9%) were G849A nonsense mutation (se4), 4/202 (1.9%) were G428A nonsense mutation (se1), and 81/202 (40.1%) were wild-type allele (Se). No C628T nonsense mutations (se5) or fusion genes of pseudogene and FUT2 gene (se 6) were found in this population. For the molecular basis of phenotype Le(a+ b-): eight cases had se2/se2, six cases had se2/se3, two cases had se3/se4, one case was homozygous of se4, one case was se3/se1, and two cases were se2/se7. For the Le(a+ b+) phenotype: four cases had se2/se2, two cases had se2/se3, one case was se3/se3, and one case was se2/se4. For the Le(a- b+) phenotype: 16 cases were Se/Se, 21 cases were Se/se2, six cases were Se/se3, five cases were Se/se4, and two cases had Se/se1. Our results suggest that the genotypes of the alpha(1, 2)-fucosyltransferase gene in phenotypes Le(a+ b+) and Le(a+ b-) are the same. Other factors that play important roles may cause the differences between these two phenotypes. Several hotspot mutations in the alpha(1,2)-fucosyltransferase gene are responsible for the nonsecretor phenotype.

Plasma alpha1,3-fucosyltransferase deficiency in schizophrenia

Levels of plasma alpha1,3-fucosyltransferase (alpha1,3FT) were assayed in 44 patients with schizophrenia and in 50 healthy controls. Significantly reduced enzyme activities were observed in patients (p < 0.05) and 4 unrelated patients were found, for the first time in Japan, to be deficient in the enzyme activity. Two point mutations in the coding region of the FUT6 gene encoding plasma alpha1,3FT that were responsible for the inactivation of the enzyme activity were detected in those patients. Genotyping of the Le gene (FUT3) in these patients demonstrated that 2 of them were also FUT3 deficient and were grouped as Lewis- individuals whereas the rest were Lewis+.

Missense mutation of FUT1 and deletion of FUT2 are responsible for Indian Bombay phenotype of ABO blood group system

The Bombay phenotype fails to express the ABH antigens of ABO blood group system on red blood cells and in secretions because of a lack in activities of the H gene (FUT1)- and Secretor gene (FUT2)-encoded alpha (1,2)fucosyltransferases. In this study, we have examined the FUT1 and the FUT2 from three unrelated Indian individuals with the Bombay phenotype. These three individuals were found to be homozygous for a T725G mutation in the coding region of the FUT1, which inactivated the enzyme activity. In addition, we did not detect any hybridized band corresponding to the FUT2 by Southern blot analysis using the catalytic domain of the FUT2 as a probe, indicating that the three individuals were homozygous for a gene deletion in the FUT2. These results suggest that the T725G mutation of FUT1 and the gene deletion of FUT2 are responsible for the classical Indian Bombay phenotype.

Wide variety of point mutations in the H gene of Bombay and para-Bombay individuals that inactivate H enzyme

The H genes, encoding an alpha1,2fucosyltransferase, which defines blood groups with the H structure, of four Bombay and 13 para-Bombay Japanese individuals were analyzed for mutations. Four Bombay individuals were homologous for the same null H allele, which is inactivated by a single nonsense mutation at position 695 from G to A (G695A), resulting in termination of H gene translation. The allele inactivated by the G695A was designated h1. The other 13 para-Bombay individuals possessed a trace amount of H antigens on erythrocytes regardless of their secretor status. Sequence analysis of their H genes showed four additional inactivated H gene alleles, h2, h3, h4, and h5. The h2 allele possesed a single base deletion at position 990 G (990-del). The h3 and h4 alleles possessed a single missense mutation, T721C, which changes Tyr 241 to His, and G442T, which changes Asp148 to Tyr, respectively. The h5 allele possessed two missense mutations, T460C (Tyr154to His) and G1042A (Glu348to Lys). The h2, h3, h4, and h5 enzymes directed by these alleles were not fully inactivated by the deletion and the missense mutations expressing some residual enzyme activity resulting in synthesis of H antigen on erythrocytes. Thirteen para-Bombay individuals whose erythrocytes retained a trace amount of H antigen were determined to be heterozygous or homozygous for at least one of h2, h3, h4, or h5 alleles. This clarified that the levels (null to trace amount) of H antigen expression on erythrocytes of Bombay and para-Bombay individuals are determined solely by H enzyme activity. These mutations found in the Japanese H alleles differ from a nonsense mutation found in the Indonesian population. To determine the roles of the H, Se, and Le genes in the expression of H antigen in secretions and Lewis blood group antigen on erythrocytes, the Lewis and secretor genes were also examined in these Bombay and para-Bombay individuals. The Lewis blood group phenotype, Le(alpha- b+), was determined by the combinatorial activity of two fucosyltransferases, the Lewis enzyme and the secretor enzyme, and the secretor status was solely determined by the secretor enzyme activity, not by H enzyme activity. Bombay individuals were confirmed to be homozygous for the inactivated H and Se genes. As expected from the very low frequency of Bombay and para-Bombay individuals in the population, ie, approximately one in two or 300,000, the H gene mutations were found to be very variable, unlike the cases of the point mutations in the other glycosyltransferase genes; the ABO genes, the Lewis gene, and the secretor gene.

Serologic characteristics of H-deficient phenotypes among Chinese in Hong Kong

BACKGROUND

The occasional presence of H-deficient red cells among both referred and donor blood samples prompted the mass screening of donated blood in Hong Kong for H-deficient phenotypes; 96 percent of the donors tested are Chinese from the southern province of Kwongtung.

STUDY DESIGN AND METHODS

Donor blood was screened for H-deficient red cells with the use of Ulex europaeus. Lewis phenotyping was carried out on all H-deficient individuals, and saliva testing was performed on most such individuals. The thermal amplitude and potency of their anti-H and anti-HI in the serum were also estimated.

RESULTS

Between 1984 and 1993, 28 H-deficient blood donors were identified; 16 H-deficient patient samples were also identified, and family studies revealed an additional 7 H-deficient subjects. The H-deficient red cells did not react with anti-H lectin, the levels of ABH substances in saliva were normal or near-normal, normal levels of A or B transferase were found in plasma, minute quantities of A or B (in persons who were genetically group A or B) were detected on the red cells, and anti-H or anti-HI was detected in the serum (about 66.7% of which reacted at 37 degrees C). Atypical anti-A or anti-B was demonstrated in 81.8 percent of the cases.

CONCLUSION

The H-deficient phenotype among the Hong Kong Chinese seems to represent a homogeneous group. Despite the presence of normal quantities of ABH substance in the saliva, anti-H or anti-HI that was active at 37 degrees C was detected in most cases. The incidence of the H-deficient phenotype was 1 in 15,620.

Molecular basis for secretor type alpha(1,2)-fucosyltransferase gene deficiency in a Japanese population: a fusion gene generated by unequal crossover responsible for the enzyme deficiency

About 20%-25% of Caucasian individuals are nonsecretors who fail to express soluble A, B, H, and Lewis b histo-blood group antigens in secretory organs and secretory fluids because of the absence of the Secretor gene (FUT2)-encoded alpha(1,2)-fucosyltransferase (Se enzyme) activity. Recently, the FUT2 and a pseudogene have been isolated, and an Se enzyme-deficient allele (se) caused by a nonsense mutation (G428A, se1) in Caucasians has also been reported. Although we were unable to find the se1 allele, we have found a missense mutation (A385T, se2) and two nonsense mutations (C571T, se3 and C628T, se4) in the Japanese Se enzyme-deficient alleles. In addition, we have found a fusion gene, which consisted of the 5'-region of the pseudogene and the 3'-region of the functional FUT2, as a Se enzyme-deficient allele (se5). The DNA sequence analysis of the fusion gene indicated that the crossover region corresponded to regions between bases 253 and 313 of the pseudogene and between bases 211 and 271 of the FUT2. This finding suggested that the fusion gene was generated by homologous but unequal crossover. A population study on 141 randomly selected Japanese has indicated that the se2 is a common Se enzyme-deficient allele in the Japanese population. The results suggest that Se enzyme-deficient alleles are race specific.

A missense mutation in the FUT6 gene results in total absence of alpha3-fucosylation of human alpha1-acid glycoprotein

The major alpha3-fucosyltransferase activity in human plasma is encoded by the gene for fucosyltransferase VI (FUT6). A missense mutation (Gly-739 --> Ala) in this gene is responsible for deficiency of enzyme activity in plasma. To examine whether this fucosyltransferase is the sole enzyme responsible for the alpha3-fucosylation of serum glycoproteins in the liver, we studied the fucosylation of three glycoproteins in sera of individuals with or without inactivated FUT3 and/or FUT6 gene(s) but with a functional FUT5 gene. alpha1-Acid glycoprotein was used as the principal reporter protein for liver alpha3-fucosyltransferase activity, because of its high fucose content. In all individuals with the FUT6 missense mutation Gly-739 --> Ala in double dose, no fucosylation of alpha1-acid glycoprotein was found. This alpha1-acid glycoprotein was not intrinsically resistant to fucosylation, since it was susceptible to in vitro fucosylation using an alpha3/4-fucosyltransferase isolated from human milk. The same result was found for alpha1-antichymotrypsin and alpha1-protease inhibitor. On the other hand in all individuals with alpha3-fucosyltransferase activity in plasma, alpha3-fucosylated glycoforms of the glycoproteins studied were found. The degree of fucosylation of alpha1-acid glycoprotein was correlated with alpha3-fucosyltransferase activity (Rs = 0.82). These data indicate that the product of FUT6, but not of FUT3 or of FUT5, is responsible for the alpha3-fucosylation of glycoproteins produced in liver and suggest that this organ is a major source of alpha3-fucosyltransferase activity in plasma.

Molecular genetics of H, Se, Lewis and other fucosyltransferase genes

Seven human fucosyltransferase genes have been cloned and registered in the Genome Data Base (GDB) as FUT1 to FUT7. According to their acceptor specificity, two main groups of enzymes can be distinguished. The alpha-2-fucosyltransferases: FUT1 (H) of red cells and vascular endothelium and FUT2 (Se) of exocrine secretions. The alpha-3-fucosyltransferases: FUT3 (Lewis) of exocrine secretions; FUT4 (myeloid) of white cells and brain; FUT5 whose tissue distribution has not been defined as yet; FUT6 (plasma) present in plasma, renal proximal tubules and hepatocytes; FUT7 (leukocyte) found in neutrophils. A high DNA sequence homology has been detected among the genes within each of these two groups, while no homology has been detected between the genes of the two groups. Point mutations responsible of inactivating genetic polymorphisms have been found for FUT1, FUT2, FUT3 and FUT6, while FUT4 and FUT7 seem to be genetically monomorphic. FUT4 has been detected in all tissues of 5 to 10 weeks old human embryos suggesting that it may play a role in development. FUT7 is a candidate for the control of the synthesis of the receptors of selectin mediated cell adhesion.

Molecular basis for H blood group deficiency in Bombay (Oh) and para-Bombay individuals

The penultimate step in the biosynthesis of the human ABO blood group oligosaccharide antigens is catalyzed by alpha-(1,2)-fucosyltransferase(s) (GDP-L-fucose: beta-D-galactoside 2-alpha-L-fucosyltransferase, EC 2.4.1.69), whose expression is determined by the H and Secretor (SE) blood group loci (also known as FUT1 and FUT2, respectively). These enzymes construct Fuc alpha 1-->2Gal beta-linkages, known as H determinants, which are essential precursors to the A and B antigens. Erythrocytes from individuals with the rare Bombay and para-Bombay blood group phenotypes are deficient in H determinants, and thus A and B determinants, as a consequence of apparent homozygosity for null alleles at the H locus. We report a molecular analysis of a human alpha-(1,2)-fucosyltransferase gene, thought to correspond to the H blood group locus, in a Bombay pedigree and a para-Bombay pedigree. We find inactivating point mutations in the coding regions of both alleles of this gene in each H-deficient individual. These results define the molecular basis for H blood group antigen deficiency in Bombay and para-Bombay phenotypes, provide compelling evidence that this gene represents the human H blood group locus, and strongly support a hypothesis that the H and SE loci represent distinct alpha-(1,2)-fucosyltransferase genes. Candidate sequences for the human SE locus are identified by low-stringency Southern blot hybridization analyses, using a probe derived from the H alpha-(1,2)-fucosyltransferase gene.