Widespread gene conversion of alpha-2-fucosyltransferase genes in mammals

Expression Analysis and the Roles of the Sec1 Gene in Regulating the Composition of Mouse Gut Microbiota

The Sec1 gene encodes galactose 2-L-fucosyltransferase, whereas expression during development of the Sec1 gene mouse and its effect on the composition of the gut microbiota have rarely been reported. In this study, we examined Sec1 gene expression during mouse development, constructed Sec1 knockout mice, and sequenced their gut microbial composition. It was found that Sec1 was expressed at different stages of mouse development. Sec1 knockout mice have significantly higher intraperitoneal fat accumulation and body weight than wild-type mice. Analysis of gut microbial composition in Sec1 knockout mice revealed that at the phylum level, Bacteroidetes accounted for 68.8%and 68.3% of gut microbial composition in the Sec1-/- and Sec1+/+ groups, respectively, and Firmicutes accounted for 27.1% and 19.7%, respectively; while Firmicutes/Bacteroidetes were significantly higher in Sec1-/- mice than in Sec1+/+ mice (39.4% vs. 28.8%). In verucomicrobia, it was significantly higher in Sec1-/- mice than in Sec1+/+ group mice. At the family level, the dominant bacteria Prevotellaceae, Akkermansiaceae, Bacteroidaceae, and Lacilltobacaceae were found to be significantly reduced in the gut of Sec1-/- mice among Sec1+/+ gut microbes, while Lachnospiraceae, Ruminococcaceae, Rikenellaceae, Helicobacteraceae, and Tannerellaceae were significantly increased. Indicator prediction also revealed the dominant bacteria Akkermansiaceae and Lactobacillaceae in Sec1+/+ gut microorganisms, while the dominant bacteria Rikenellaceae, Marinifilaceae, ClostridialesvadinBB60aceae, Erysipelotrichaceae, Saccharimonadaceae, Clostridiaceae1, and Christensenellaceae in Sec1-/- group. This study revealed that the Sec1 gene was expressed in different tissues at different time periods in mice, and Sec1 knockout mice had significant weight gain, significant abdominal fat accumulation, and significant changes in gut microbial flora abundance and metabolic function, providing a theoretical basis and data support for the study of Sec1 gene function and effects on gut microbiota-related diseases.

Role of tumor cell sialylation in pancreatic cancer progression

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest malignancies and is currently the third leading cause of cancer death. The aggressiveness of PDAC stems from late diagnosis, early metastasis, and poor efficacy of current chemotherapies. Thus, there is an urgent need for effective biomarkers for early detection of PDAC and development of new therapeutic strategies. It has long been known that cellular glycosylation is dysregulated in pancreatic cancer cells, however, tumor-associated glycans and their cognate glycosylating enzymes have received insufficient attention as potential clinical targets. Aberrant glycosylation affects a broad range of pathways that underpin tumor initiation, metastatic progression, and resistance to cancer treatment. One of the prevalent alterations in the cancer glycome is an enrichment in a select group of sialylated glycans including sialylated, branched N-glycans, sialyl Lewis antigens, and sialylated forms of truncated O-glycans such as the sialyl Tn antigen. These modifications affect the activity of numerous cell surface receptors, which collectively impart malignant characteristics typified by enhanced cell proliferation, migration, invasion and apoptosis-resistance. Additionally, sialic acids on tumor cells engage inhibitory Siglec receptors on immune cells to dampen anti-tumor immunity, further promoting cancer progression. The goal of this review is to summarize the predominant changes in sialylation occurring in pancreatic cancer, the biological functions of sialylated glycoproteins in cancer pathogenesis, and the emerging strategies for targeting sialoglycans and Siglec receptors in cancer therapeutics.

Possible Link Between the ABO Blood Group of Bioprosthesis Recipients and Specific Types of Structural Degeneration

Background Pigs/bovines share common antigens with humans: α-Gal, present in all pigs/bovines close to the human B-antigen; and AH-histo-blood-group antigen, identical to human AH-antigen and present only in some animals. We investigate the possible impact of patients' ABO blood group on bioprosthesis structural valve degeneration (SVD) through calcification/pannus/tears/perforations for patients ≤60 years at implantation. Methods and Results This was a single-center study (Paris, France) that included all degenerative bioprostheses explanted between 1985 and 1998, mostly porcine bioprostheses (Carpentier-Edwards second/third porcine bioprostheses) and some bovine bioprostheses. For the period 1998 to 2014, only porcine bioprostheses with longevity ≥13 years were included (total follow-up ≥29 years). Except for blood groups, important predictive factors for SVD were prospectively collected (age at implantation/longevity/number/site/sex/SVD types) and analyzed using logistic regression. All variables were available for 500 explanted porcine bioprostheses. By multivariate analyses, the A group was associated with an increased risk of: tears (odds ratio[OR], 1.61; P=0.026); pannus (OR, 1.5; P=0.054), pannus with tears (OR, 1.73; P=0.037), and tendency for lower risk of: calcifications (OR, 0.63; P=0.087) or isolated calcification (OR, 0.67; P=0.17). A-antigen was associated with lower risk of perforations (OR 0.56; P=0.087). B-group patients had an increased risk of: perforations (OR, 1.73; P=0.043); having a pannus that was calcified (OR, 3.0, P=0.025). B-antigen was associated with a propensity for calcifications in general (OR, 1.34; P=0.25). Conclusions Patient's ABO blood group is associated with specific SVD types. We hypothesize that carbohydrate antigens, which may or may not be common to patient and animal bioprosthetic tissue, will determine a patient's specific immunoreactivity with respect to xenograft tissue and thus bioprosthesis outcome in terms of SVD.

Fucosyltransferase gene expression in goat endometrium during the estrous cycle and early pregnancy

Regulation of the expression of the alpha(1,2)fucosyltransferase (FUT) genes and their enzymatic products, including the H-type 1 antigen (HT1), on the luminal surface of the uterus is believed to be critical for establishment of pregnancy in mammals. The FUT1 gene is a marker for conception rates in dairy cows and HT1 is a marker for uterine receptivity in rodents. To determine the spatiotemporal expression patterns of FUT1 and FUT2 genes in goats, endometrial tissues were obtained on six days spanning the estrous cycle (Days 5, 11, 13, 15, 17 and 19) and seven days spanning early pregnancy (Days 5, 11, 13, 15, 17, 19 and 25). In all data, we found no effect of status (cyclic or pregnant; P > 0.1) and pooled data where appropriate. We cloned FUT1 cDNA from goat endometrium and made probes from it for Northern and slot blot analyses. The analyses indicated that FUT1 gene expression was high until Day 13, and then declined. In situ hybridization revealed a change in the cell-specificity of FUT1 gene expression over the estrous cycle and early pregnancy. In situ hybridization signal intensity scores indicated that FUT1 expression by uterine epithelium was high on Day 5, moderate on Day 11, and minimal on subsequent days. In situ hybridization signals in uterine glandular epithelial cells remained high from Day 5 to Day 13, with weaker signals thereafter. Quantitative reverse transcription-PCR (RT-qPCR) assays were used for quantitation of FUT1 and FUT2 mRNAs. Quantitative RT-qPCR data were generated from endometrium collected from cyclic and pregnant animals on Days 5, 11 and 17. Relative levels of FUT1 mRNA were high on Days 5 and 11, but then fell 5-fold by Day 17 (P < 0.01). FUT2 mRNA concentrations were below the accurate detectable limit of the assay. High levels of HT1 were observed on the apical surface of uterine luminal epithelia on Days 5, 15, 17 and 19, with much lower levels on Days 11 and 13. Thus, data suggests that FUT1 is the primary enzyme responsible for the high levels of HT1 antigen present on the uterine luminal epithelium between Days 5 and 11 of the estrous cycle and early pregnancy. But changes in the expression of the FUT1 gene does not directly correlate to HT1 staining, which increased from Day 13-15. Future studies are required to understand the regulation of the HT1 antigen on the luminal surface of endometrium.

Recipients with blood group A associated with longer survival rates in cardiac valvular bioprostheses

Background

Pigs/bovines share with humans some of the antigens present on cardiac valves. Two such antigens are: the major xenogenic Ag, “Gal” present in all pig/bovine very close to human B-antigen of ABO-blood-group system; the minor Ag, pig histo-blood-group AH-antigen identical to human AH-antigen and present by some animals. We hypothesize that these antigens may modify the immunogenicity of the bioprosthesis and also its longevity. ABO distribution may vary between patients with low (<6 years) and high (≥15 years) bioprostheses longevity.

Methods

Single-centre registry study (Paris, France) including all degenerative porcine bioprostheses (mostly Carpentier-Edwards 2nd/3rd generation heart valves) explanted between 1985 and 1998 and some bovine bioprostheses. For period 1998–2014, all porcine bioprostheses with longevity ≥13 years (follow-up ≥29 years). Important predictive factors for bioprosthesis longevity: number, site of implantation, age were collected. Blood group and other variables were entered into an ordinal logistic regression analysis model predicting valve longevity, categorized as low (<6 years), medium (6–14.9 years), and high (≥15 years).

Findings

Longevity and ABO-blood group were obtained for 483 explanted porcine bioprostheses. Mean longevity was 10.2 ± 3.9 years [0–28] and significantly higher for A-patients than others (P = 0.009). Using multivariate analysis, group A was a strong predictive factor of longevity (OR 2.09; P < 0.001). For the 64 explanted bovine bioprosthesis with low/medium longevity, the association, with A-group was even more significant.

Interpretation

Patients of A-group but not B have a higher longevity of their bioprostheses. Future graft-host phenotyping and matching may give rise to a new generation of long-lasting bioprosthesis for implantation in humans, especially for the younger population.

Fund

None.

Fucosylation in cancer biology and its clinical applications

Fucosylation is the process of transferring fucose from GDP-fucose to their substrates, which includes certain proteins, N- and O-linked glycans in glycoprotein or glycolipids, by fucosyltransferases in all mammalian cells. Fucosylated glycans play vital role in selectin-mediated leukocyte extravasation, lymphocyte homing, and pathogen-host interactions, whereas fucosylated proteins are essential for signaling transduction in numerous ontogenic events. Aberrant fucosylation due to the availability of high energy donor GDP-fucose, abnormal expression of FUTs and/or α-fucosidase, and the availability of their substrates leads to different fucosylated glycan or protein structures. Accumulating evidence demonstrates that aberrant fucosylation plays important role in all aspects of cancer biology. In this review, we will summarize the current knowledge about fucosylation in different physiological and pathological processes with a focus on their roles not only in cancer cell proliferation, invasion, and metastasis but also in tumor immune surveillance. Furthermore, the clinical potential and applications of fucosylation in cancer diagnosis and treatment will also be discussed.

Multiple homologous genes knockout (KO) by CRISPR/Cas9 system in rabbit

The CRISPR/Cas9 system is a highly efficient and convenient genome editing tool, which has been widely used for single or multiple gene mutation in a variety of organisms. Disruption of multiple homologous genes, which have similar DNA sequences and gene function, is required for the study of the desired phenotype. In this study, to test whether the CRISPR/Cas9 system works on the mutation of multiple homologous genes, a single guide RNA (sgRNA) targeting three fucosyltransferases encoding genes (FUT1, FUT2 and SEC1) was designed. As expected, triple gene mutation of FUT1, FUT2 and SEC1 could be achieved simultaneously via a sgRNA mediated CRISPR/Cas9 system. Besides, significantly reduced serum fucosyltransferases enzymes activity was also determined in those triple gene mutation rabbits. Thus, we provide the first evidence that multiple homologous genes knockout (KO) could be achieved efficiently by a sgRNA mediated CRISPR/Cas9 system in mammals, which could facilitate the genotype to phenotype studies of homologous genes in future.

Fucosylated Antigens in Cancer: An Alliance toward Tumor Progression, Metastasis, and Resistance to Chemotherapy

Aberrant glycosylation of tumor cells is recognized as a universal hallmark of cancer pathogenesis. Overexpression of fucosylated epitopes, such as type I (H1, Lewis^a, Lewis^b, and sialyl Lewis^a) and type II (H2, Lewis^x, Lewis^y, and sialyl Lewis^x) Lewis antigens, frequently occurs on the cancer cell surface and is mainly attributed to upregulated expression of pertinent fucosyltransferases (FUTs). Nevertheless, the impact of fucose-containing moieties on tumor cell biology is not fully elucidated yet. Here, we review the relevance of tumor-overexpressed FUTs and their respective synthesized Lewis determinants in critical aspects associated with cancer progression, such as increased cell survival and proliferation, tissue invasion and metastasis, epithelial to mesenchymal transition, epithelial and immune cell interaction, angiogenesis, multidrug resistance, and cancer stemness. Furthermore, we discuss the potential use of enhanced levels of fucosylation as glycan biomarkers for early prognosis, diagnosis, and disease monitoring in cancer patients.

An overview of the lagomorph immune system and its genetic diversity

Our knowledge of the lagomorph immune system remains largely based upon studies of the European rabbit (Oryctolagus cuniculus), a major model for studies of immunology. Two important and devastating viral diseases, rabbit hemorrhagic disease and myxomatosis, are affecting European rabbit populations. In this context, we discuss the genetic diversity of the European rabbit immune system and extend to available information about other lagomorphs. Regarding innate immunity, we review the most recent advances in identifying interleukins, chemokines and chemokine receptors, Toll-like receptors, antiviral proteins (RIG-I and Trim5), and the genes encoding fucosyltransferases that are utilized by rabbit hemorrhagic disease virus as a portal for invading host respiratory and gut epithelial cells. Evolutionary studies showed that several genes of innate immunity are evolving by strong natural selection. Studies of the leporid CCR5 gene revealed a very dramatic change unique in mammals at the second extracellular loop of CCR5 resulting from a gene conversion event with the paralogous CCR2. For the adaptive immune system, we review genetic diversity at the loci encoding antibody variable and constant regions, the major histocompatibility complex (RLA) and T cells. Studies of IGHV and IGKC genes expressed in leporids are two of the few examples of trans-species polymorphism observed outside of the major histocompatibility complex. In addition, we review some endogenous viruses of lagomorph genomes, the importance of the European rabbit as a model for human disease studies, and the anticipated role of next-generation sequencing in extending knowledge of lagomorph immune systems and their evolution.

Multiple conversion between the genes encoding bacterial class-I release factors

Bacteria require two class-I release factors, RF1 and RF2, that recognize stop codons and promote peptide release from the ribosome. RF1 and RF2 were most likely established through gene duplication followed by altering their stop codon specificities in the common ancestor of extant bacteria. This scenario expects that the two RF gene families have taken independent evolutionary trajectories after the ancestral gene duplication event. However, we here report two independent cases of conversion between RF1 and RF2 genes (RF1-RF2 gene conversion), which were severely examined by procedures incorporating the maximum-likelihood phylogenetic method. In both cases, RF1-RF2 gene conversion was predicted to occur in the region encoding nearly entire domain 3, of which functions are common between RF paralogues. Nevertheless, the ‘direction’ of gene conversion appeared to be opposite from one another—from RF2 gene to RF1 gene in one case, while from RF1 gene to RF2 gene in the other. The two cases of RF1-RF2 gene conversion prompt us to propose two novel aspects in the evolution of bacterial class-I release factors: (i) domain 3 is interchangeable between RF paralogues, and (ii) RF1-RF2 gene conversion have occurred frequently in bacterial genome evolution.

Neofunctionalization of the Sec1 α1,2fucosyltransferase paralogue in leporids contributes to glycan polymorphism and resistance to rabbit hemorrhagic disease virus

RHDV (rabbit hemorrhagic disease virus), a virulent calicivirus, causes high mortalities in European rabbit populations (Oryctolagus cuniculus). It uses α1,2fucosylated glycans, histo-blood group antigens (HBGAs), as attachment factors, with their absence or low expression generating resistance to the disease. Synthesis of these glycans requires an α1,2fucosyltransferase. In mammals, there are three closely located α1,2fucosyltransferase genes rSec1, rFut2 and rFut1 that arose through two rounds of duplications. In most mammalian species, Sec1 has clearly become a pseudogene. Yet, in leporids, it does not suffer gross alterations, although we previously observed that rabbit Sec1 variants present either low or no activity. Still, a low activity rSec1 allele correlated with survival to an RHDV outbreak. We now confirm the association between the α1,2fucosyltransferase loci and survival. In addition, we show that rabbits express homogenous rFut1 and rFut2 levels in the small intestine. Comparison of rFut1 and rFut2 activity showed that type 2 A, B and H antigens recognized by RHDV strains were mainly synthesized by rFut1, and all rFut1 variants detected in wild animals were equally active. Interestingly, rSec1 RNA levels were highly variable between individuals and high expression was associated with low binding of RHDV strains to the mucosa. Co-transfection of rFut1 and rSec1 caused a decrease in rFut1-generated RHDV binding sites, indicating that in rabbits, the catalytically inactive rSec1 protein acts as a dominant-negative of rFut1. Consistent with neofunctionalization of Sec1 in leporids, gene conversion analysis showed extensive homogenization between Sec1 and Fut2 in leporids, at variance with its limited degree in other mammals. Gene conversion additionally involving Fut1 was also observed at the C-terminus. Thus, in leporids, unlike in most other mammals where it became extinct, Sec1 evolved a new function with a dominant-negative effect on rFut1, contributing to fucosylated glycan diversity, and allowing herd protection from pathogens such as RHDV.

There are three members of the α1,2fucosyltransferases gene family in mammalian genomes, Fut1, Fut2 and Sec1. The encoded fucosyltransferases are key enzymes for the synthesis of glycans that can be used as ligands by pathogens. However, the polymorphism of expression of these fucosylated glycans on epithelial cell types contributes to protection at the species level. In most mammalian species Sec1 is a pseudogene and in humans, genetic variation of α1,2fucosylated glycans is provided by FUT2 polymorphisms. Rabbit haemorrhagic disease virus (RHDV) uses α1,2fucosylated glycans as attachment factors. It induces an acute disease with very high mortalities in rabbit populations. We now confirm an association between genetic markers in the rabbit Sec1-Fut2 genomic region and survival to RHDV. We show that the Fut1 gene is the main contributor to the synthesis of RHDV binding sites although individual variation is not achieved by Fut1 polymorphisms but by variation in levels of Sec1 transcription. The Sec1 protein acting as a dominant-negative of Fut1, high Sec1 expression leads to a decreased number of RHDV binding sites. Thus, unlike in other mammals, in rabbits Sec1 underwent neofunctionalization. It contributes to generate diversity of fucosylated glycans, a key mechanism for escaping pathogens such as RHDV.

The non-pathogenic Australian rabbit calicivirus RCV-A1 provides temporal and partial cross protection to lethal Rabbit Haemorrhagic Disease Virus infection which is not dependent on antibody titres

The endemic non-pathogenic Australian rabbit calicivirus RCV-A1 is known to provide some cross protection to lethal infection with the closely related Rabbit Haemorrhagic Disease Virus (RHDV). Despite its obvious negative impacts on viral biocontrol of introduced European rabbits in Australia, little is known about the extent and mechanisms of this cross protection. In this study 46 rabbits from a colony naturally infected with RCV-A1 were exposed to RHDV. Survival rates and survival times did not correlate with titres of serum antibodies specific to RCV-A1 or cross reacting to RHDV, but were instead influenced by the time between infection with the two viruses, demonstrating for the first time that the cross protection to lethal RHDV infection is transient. These findings are an important step towards a better understanding of the complex interactions of co-occurring pathogenic and non-pathogenic lagoviruses.

In silico analysis of the fucosylation-associated genome of the human blood fluke Schistosoma mansoni: cloning and characterization of the fucosyltransferase multigene family

Fucosylated glycans of the parasitic flatworm Schistosoma mansoni play key roles in its development and immunobiology. In the present study we used a genome-wide homology-based bioinformatics approach to search for genes that contribute to fucosylated glycan expression in S. mansoni, specifically the α2-, α3-, and α6-fucosyltransferases (FucTs), which transfer L-fucose from a GDP-L-fucose donor to an oligosaccharide acceptor. We identified and in silico characterized several novel schistosome FucT homologs, including six α3-FucTs and six α6-FucTs, as well as two protein O-FucTs that catalyze the unrelated transfer of L-fucose to serine and threonine residues of epidermal growth factor- and thrombospondin-type repeats. No α2-FucTs were observed. Primary sequence analyses identified key conserved FucT motifs as well as characteristic transmembrane domains, consistent with their putative roles as fucosyltransferases. Most genes exhibit alternative splicing, with multiple transcript variants generated. A phylogenetic analysis demonstrated that schistosome α3- and α6-FucTs form monophyletic clades within their respective gene families, suggesting multiple gene duplications following the separation of the schistosome lineage from the main evolutionary tree. Quantitative decreases in steady-state transcript levels of some FucTs during early larval development suggest a possible mechanism for differential expression of fucosylated glycans in schistosomes. This study systematically identifies the complete repertoire of FucT homologs in S. mansoni and provides fundamental information regarding their genomic organization, genetic variation, developmental expression, and evolutionary history.

[Genetic susceptibility to norovirus infection]

Norovirus (NoV) are the most common cause of acute gastroenteritidis in humans worldwide. They are transmitted through consumption of contaminated food, or mostly by direct person-to-person contact. However, susceptibility to NoV infection is variable. NoVs recognize carbohydrate ligand, including A, B, H and Lewis histoblood group antigen (HBGAs) for attachment to human epithelial cells. Synthesis of these HBGAs requires various glycosyltransferase encoded by the ABO, FUT2, FUT3 genes. The presence of distinct carbohydrates structures dependent upon the combined polymorphism at the FUT2, FUT3 and ABO loci influences susceptibility to NoV infection. NoV-glycan interactions studies show that different strains recognize specific HBGAs. Together with herd immunity, HBGAs play a major role in the epidemiology and evolution of NoVs.

Rabbit haemorrhagic disease (RHD) and rabbit haemorrhagic disease virus (RHDV): a review

Rabbit haemorrhagic disease virus (RHDV) is a calicivirus of the genus Lagovirus that causes rabbit haemorrhagic disease (RHD) in adult European rabbits (Oryctolagus cuniculus). First described in China in 1984, the virus rapidly spread worldwide and is nowadays considered as endemic in several countries. In Australia and New Zealand where rabbits are pests, RHDV was purposely introduced for rabbit biocontrol. Factors that may have precipitated RHD emergence remain unclear, but non-pathogenic strains seem to pre-date the appearance of the pathogenic strains suggesting a key role for the comprehension of the virus origins. All pathogenic strains are classified within one single serotype, but two subtypes are recognised, RHDV and RHDVa. RHD causes high mortality in both domestic and wild adult animals, with individuals succumbing between 48-72 h post-infection. No other species has been reported to be fatally susceptible to RHD. The disease is characterised by acute necrotising hepatitis, but haemorrhages may also be found in other organs, in particular the lungs, heart, and kidneys due to disseminated intravascular coagulation. Resistance to the disease might be explained in part by genetically determined absence or weak expression of attachment factors, but humoral immunity is also important. Disease control in rabbitries relies mainly on vaccination and biosecurity measures. Such measures are difficult to be implemented in wild populations. More recent research has indicated that RHDV might be used as a molecular tool for therapeutic applications. Although the study of RHDV and RHD has been hampered by the lack of an appropriate cell culture system for the virus, several aspects of the replication, epizootology, epidemiology and evolution have been disclosed. This review provides a broad coverage and description of the current knowledge on the disease and the virus.

A novel FUT1 allele was identified in a Chinese individual with para-Bombay phenotype

BACKGROUND

The para-Bombay phenotype is characterised by H-deficient or H partially deficient red blood cells (RBCs) in individuals who secrete ABH antigens in their saliva. Samples from an individual whose RBCs had an apparent para-Bombay phenotype and his family members were investigated and a novel FUT1 allele was identified.

MATERIALS AND METHODS

RBCs' phenotype was characterised by standard serologic technique. Genomic DNA was sequenced with primers that amplified the coding sequence of FUT1 and FUT2, respectively. Routine ABO genotyping analysis was performed. Haplotypes of FUT1 were identified by TOPO cloning sequencing. Recombination expression vectors of FUT1 mutation alleles were constructed and transfected into COS-7 cells. The pα-(1,2)-fucosyltransferase activity of expression protein was determined.

RESULTS

B101/O02 genotype of the proband was correlated with ABH substances in saliva. The proband carried a new FUT1 allele which showed 35C/T, 235G/C and 682A/G heterozygote by directly DNA sequencing. Two haplotypes, 235C and 35T+682G, were identified by TOPO cloning sequencing and COS-7 cells transfected with five recombination vectors including wild-type, 35T, 235C, 682G and 35T+682G alleles were established respectively. The α-(1,2)-fucosyltransferase activities of cell lysates which had transfected with 35T, 235C, 682G and 35T+682G recombination vectors showed 79·45, 16·23, 80·32 and 24·59%, respectively, compared with that of the wild-type FUT1-transfected cell lysates.

CONCLUSION

A novel FUT1 allele 235C was identified, which greatly diminished the activity of α-(1,2)-fucosyltransferase.

Colonic mucosa-associated microbiota is influenced by an interaction of Crohn disease and FUT2 (Secretor) genotype

The FUT2 (Secretor) gene is responsible for the presence of ABO histo-blood group antigens on the gastrointestinal mucosa and in bodily secretions. Individuals lacking a functional copy of FUT2 are known as "nonsecretors" and display an array of differences in susceptibility to infection and disease, including Crohn disease. To determine whether variation in resident microbial communities with respect to FUT2 genotype is a potential factor contributing to susceptibility, we performed 454-based community profiling of the intestinal microbiota in a panel of healthy subjects and Crohn disease patients and determined their genotype for the primary nonsecretor allele in Caucasian populations, W143X (G428A). Consistent with previous studies, we observe significant deviations in the microbial communities of individuals with Crohn disease. Furthermore, the FUT2 genotype explains substantial differences in community composition, diversity, and structure, and we identified several bacterial species displaying disease-by-genotype associations. These findings indicate that alterations in resident microbial communities may in part explain the variety of host susceptibilities surrounding nonsecretor status and that FUT2 is an important genetic factor influencing host-microbial diversity.

Histo-blood group antigens act as attachment factors of rabbit hemorrhagic disease virus infection in a virus strain-dependent manner

Rabbit Hemorrhagic disease virus (RHDV), a calicivirus of the Lagovirus genus, and responsible for rabbit hemorrhagic disease (RHD), kills rabbits between 48 to 72 hours post infection with mortality rates as high as 50–90%. Caliciviruses, including noroviruses and RHDV, have been shown to bind histo-blood group antigens (HBGA) and human non-secretor individuals lacking ABH antigens in epithelia have been found to be resistant to norovirus infection. RHDV virus-like particles have previously been shown to bind the H type 2 and A antigens. In this study we present a comprehensive assessment of the strain-specific binding patterns of different RHDV isolates to HBGAs. We characterized the HBGA expression in the duodenum of wild and domestic rabbits by mass spectrometry and relative quantification of A, B and H type 2 expression. A detailed binding analysis of a range of RHDV strains, to synthetic sugars and human red blood cells, as well as to rabbit duodenum, a likely gastrointestinal site for viral entrance was performed. Enzymatic cleavage of HBGA epitopes confirmed binding specificity. Binding was observed to blood group B, A and H type 2 epitopes in a strain-dependent manner with slight differences in specificity for A, B or H epitopes allowing RHDV strains to preferentially recognize different subgroups of animals. Strains related to the earliest described RHDV outbreak were not able to bind A, whereas all other genotypes have acquired A binding. In an experimental infection study, rabbits lacking the correct HBGA ligands were resistant to lethal RHDV infection at low challenge doses. Similarly, survivors of outbreaks in wild populations showed increased frequency of weak binding phenotypes, indicating selection for host resistance depending on the strain circulating in the population. HBGAs thus act as attachment factors facilitating infection, while their polymorphism of expression could contribute to generate genetic resistance to RHDV at the population level.

Rabbit hemorrhagic disease virus (RHDV), detected as late as 1984, has spread to large parts of the world, threatening rabbit populations and other species dependent on rabbits in many European countries. Mortality has been shown to be as high as 90% and rabbits are killed 48 to 72 hours after infection. Related viruses called noroviruses, infect humans in a manner dependent on the expression of histo-blood group antigens (HBGAs), which are not only expressed on red blood cells, but also on epithelial cells, in saliva and on mucins of the intestinal tract. RHDV also binds to HBGA and in this report we characterize binding of strains of all genetic groups of RHDV to different HBGAs. We also demonstrate HBGAs to function as attachment factors in a challenge experiment. As polymorphisms of genes involved in HBGA synthesis divide the rabbit population into different subgroups, we find selection of low-binding subgroups of wild rabbits in populations recovering from devastating outbreaks of RHDV. This is the first demonstration of differential HBGA specificities of RHDV strains, description of function in infection and demonstration of host selection due to RHDV infection based on HBGA phenotype.

Patterns of human genetic variation inferred from comparative analysis of allelic mutations in blood group antigen genes

Comparative analysis of allelic variation of a gene sheds light on the pattern and process of its diversification at the population level. Gene families for which a large number of allelic forms have been verified by sequencing provide a useful resource for such studies. In this regard, human blood group-encoding genes are unique in that differences of cell surface traits among individuals and populations can be readily detected by serological screening, and correlation between the variant cell surface phenotype and the genotype is, in most cases, unequivocal. Here, we perform a comprehensive analysis of allelic forms, compiled in the Blood Group Antigen Gene Mutation database, of ABO, RHD/CE, GYPA/B/E and FUT1/2 gene families that encode the ABO, RH, MNS, and H/h blood group system antigens, respectively. These genes are excellent illustrative examples showing distinct mutational patterns among the alleles, and leading to speculation on how their origin may have been driven by recurrent but different molecular mechanisms. We illustrate how alignment of alleles of a gene may provide an additional insight into the DNA variation process and its pathways, and how this approach may serve to catalog alleles of a gene, simplifying the task and content of mutation databases.

RNA-mediated gene silencing of FUT1 and FUT2 influences expression and activities of bovine and human fucosylated nucleolin and inhibits cell adhesion and proliferation

In a previous article, we demonstrated the existence of fucosyl-containing O-glycans forms of nucleolin in bovine post-capillary venular endothelial cells (CVEC) and malignant cultured human A431 cells. The tool for this discovery was an antibody found to interact strongly and exclusively with nucleolin in total protein extracts. The antibody was originally raised against a mollusc glycoprotein and was demonstrated to be directed against its O-glycans, recently found to belong prevalently to the blood group H-antigen type with fucose linked in alpha1, 2 to galactose. Here, we show that si-RNA induced down-regulation of the expression of FUT1 and FUT2, the fucosyltransferases required for the biosynthesis of the terminal glycan motif Fucalpha-2-Galbeta-R, reduced expression of the fucosylated nucleolin glycoforms and their exposure at the cell surface in CVEC. Treatment of the cells with FUT1/2 siRNA also reduced their ability to bind and internalize endostatin and their adhesion efficiency and inhibited cell growth. Expression of FUT1, FUT2, and FUT6 was also analyzed in serum-stimulated versus serum-starved cells and in cells treated with FUT1 and FUT2 siRNA. A reduced expression of fucosylated nucleolin and inhibition of cell growth by suppressing FUT1/2 expression was also tested and shown to be exhibited in human A431 cells.