Five novel missense mutations of the Lewis gene (FUT3) in African (Xhosa) and Caucasian populations in South Africa

Genetic variation of FUT3 gene in the Han population from Northern China

BACKGROUND AND OBJECTIVES

The FUT3 gene encodes α(1,3/1,4)-fucosyltransferase, which is a crucial enzyme in the synthesis of Lewis antigens. FUT3 gene variants show race-specific differences. In this study, we conducted a systematic sequence analysis of the FUT3 coding sequence. The objective was to explore genetic variations of the FUT3 gene within the Han population of Northern China.

MATERIALS AND METHODS

A cohort of 313 blood donors was recruited for the study. The coding sequence of the FUT3 gene was amplified using polymerase chain reaction, followed by sequencing and haplotype construction.

RESULTS

Twelve single nucleotide variations (SNVs) were identified within the coding sequence of the FUT3 gene. Notably, the c.59 T > G site exhibited the highest mutation frequency of 43.13%, followed by the c.508G > A and c.1067 T > A sites with mutation frequencies of 27.48% and 16.93%, respectively. Le was the most common haplotype, accounting for 67.57% of the cases, and Le/Le was the most common diplotype, accounting for 46.33% of the cases. The study also highlighted a significant difference in mutation frequencies of FUT3 gene between the Han Chinese of Northern China and the Dai of Xishuangbanna, China, but not the Han Chinese in Beijing in the North and the Southern Han Chinese, emphasising that Han Chinese in Northern China are genetically most distant from Europeans and closest to East Asians.

CONCLUSIONS

Our study characterises FUT3 gene variations in Han Chinese from Northern China, and provides basic genetic data for genetics, forensic medicine, and genotyping of Lewis blood groups.

ABO blood types, but not Secretor or Lewis blood types, influence strength of antibody response to Hepatitis B vaccine in Black South African children

Subunit vaccines for the Hepatitis B virus (HBV) have greatly reduced the prevalence of infection and morbidity through HBV-related liver cirrhosis and cancer. However, strength of immune response to vaccination varies considerably. While it is known that ABO blood types may influence HBV infection risk, the role of ABO and related blood types in strength of immune response to HBV vaccine has not been investigated. We examined 16 polymorphisms in the ABO, FUT2, and FUT3 genes and their related phenotypes for associations with strength of antibody response to HBV vaccine in Black South African infants. Anti-HBc and anti-HBs antibody levels were measured by CMIA assay 1-3 months after the last dose of HBV vaccine. Prior infection occurred in 8/207 individuals (3.86%) who were removed from further study. Of the remaining 199 individuals, 83.4% individuals were strong responders (anti-HBs ≥ 100 mIU/ml, median 973 mIU/ml), another 15.6% were weak responders (anti-HBs < 100 mIU/ml, median 50 mIU/ml) and 1% were non-responders (anti-HBs < 10 mIU/ml). The frequency of weak responders to HBV vaccine was not significantly affected by sex, birthweight, use of an additional booster dose of vaccine or cohort of origin. We characterised patterns of genetic variation present at the ABO, FUT2 and FUT3 loci by use of MassArray genotyping and used these data to predict ABO, Secretor and Lewis phenotypes. We observed significant association of ABO blood type with strength of antibody response to HBV vaccine in a Black South African cohort (p = 0.002). In particular, presence of rs8176747G and expression of B antigen (whether in B blood type or AB blood type) was associated with decreased antibody response to HBV vaccine. Secretor and Lewis blood types were not associated with antibody response to HBV vaccine. This work increases our understanding of the impact that host genetic variation may have on vaccine immunogenicity.

Fluorescence Melting Curve Analysis for Concurrent Genotyping of Three Tag SNPs in FUT3

The synthesis of Lewis blood group antigens is governed by two fucosyltransferase genes, FUT2 and FUT3. Evidence is accumulating to suggest that functional polymorphisms of FUT2 and FUT3 are associated with a variety of clinical conditions. Fluorescence melting curve analysis (FMCA), using three different dual-labeled probes for concurrent genotyping of three single nucleotide polymorphisms (SNPs) of FUT3, c.59T>G, c.314C>T, and c.484G>A for Lewis-negative allele inference, was developed and validated using Ghanaian and Caucasian subjects. Although two other SNPs, c.55G>A, and c.61C>T, are located in the probe sequence for c.59T>G, it seems feasible to detect these two SNPs along with c.59T>G. The results obtained by probe-based FMCA were in perfect accordance with those obtained by Sanger sequencing for 106 Ghanaians and 100 Caucasians. The present method is useful and reliable for estimating Lewis-negative alleles on a relatively large scale.

ABO, secretor, and Lewis carbohydrate histo-blood groups are associated with autoimmune neutropenia of early childhood in Danish patients

Background

Autoimmune neutropenia of early childhood (AIN) is caused by autoantibodies directed against antigens on the neutrophil membrane. The ABO, secretor, and Lewis histo‐blood group systems control the expression of carbohydrate antigens and have previously been linked to autoimmune diseases. We aimed to investigate the association between genotypes and the risk of AIN in Danish patients.

Study Design and Methods

One hundred fifty‐four antibody‐positive AIN patients were included. Controls (n = 400) were healthy unrelated Danish blood donors. Molecular determination of ABO, secretor (FUT2), and Lewis (FUT3) genotypes were determined using real‐time polymerase chain reaction (qPCR) or Sanger sequencing to infer the prevalence of Lewis antigens (Le^a and Le^b) and secretor (SeSe or Sese) or nonsecretor (sese) phenotypes.

Results

Blood type O was more common in controls (46.8%) than in AIN patients (36.4%) (OR = 0.65; p = 0.028). Secretors of H Le^b antigens were less frequent among AIN patients (25.2%) than controls (35.0%) (OR = 0.62; p = 0.037).

Discussion

ABO blood group antigens and the secretion of these antigens are associated with a diagnosis of AIN. The mechanism underlying the association between autoimmunity and interaction among ABO, secretor, and Lewis genotypes has not yet been elucidated, but several studies indicate a connection to the gut microbiota.

Estimation of Lewis-negative alleles by high-resolution melting analysis of three tag SNPs of FUT3

BACKGROUND AND OBJECTIVES

The expression of type 1 chain Lewis blood group antigens is regulated by secretor-type α(1,2)fucosyltransferase, encoded by FUT2, and Lewis α(1,3/1,4)fucosyltransferase, encoded by FUT3. Accumulating evidence has linked Lewis phenotypes or genotypes to various clinical conditions. Thus, in addition to FUT2, large-scale FUT3 genotyping is important. Because FUT3 has two paralogous genes (FUT5 and FUT6) with high DNA sequence similarity, we should select the polymerase chain reaction (PCR) primers carefully for FUT3 genotyping. Previously, we suggested that 13G>A (rs28362458), 59T>G (rs28362459) and 202T>C (rs812936) could be selected as tag single nucleotide polymorphisms (SNPs) for detection of Lewis-negative alleles (le).

MATERIALS AND METHODS

In this study, three high-resolution melting (HRM) analyses for genotyping these SNPs were developed and applied for 140 Japanese, eight Ghanaians and four Sinhalese subjects.

RESULTS

Each of three genotypes of 13G>A (G/G, G/A, A/A), 59T>G (T/T, T/G, G/G) and 202T>C (T/T, T/C, C/C) was discriminated clearly. Although we need to be careful in interpretation of results due to SNPs other than the 59T>G in the amplicon, the results of 59T>G genotyping were in full agreement with the results by a previous PCR-restriction fragment length polymorphism analysis in 140 Japanese. In addition, three heterozygotes of 202C substitution were identified, and no one having a 13A substitution was found in 140 Japanese.

CONCLUSION

The present HRM analyses are useful and reliable methods for large-scale estimation of le alleles.

Norovirus infection and HBGA host genetic susceptibility in a birth community-cohort, Rio de Janeiro, Brazil

Norovirus has emerged as an important viral agent of acute pediatric gastroenteritis, with a growing genetic diversity reported in the last decades. Histo-blood group antigens (HBGAs) present on the surface of enterocytes are susceptibility factors for norovirus infection and differ between populations which could affects the epidemiology and evolution of these viruses. This study investigated the frequency, incidence and genetic diversity of noroviruses in a cohort of rotavirus A vaccinated children in association to the host HBGA (Secretor/Lewis) genetic susceptibility profile. Norovirus genogroups I and II (GI/GII) were screened by RT-qPCR in 569 stool samples from 132 children followed-up from birth to 11 months of age during 2014--2018. Noroviruses were identified in 21.2% of children enrolled in this study, with a norovirus detection rate of 5.6% (32/569), in 17.1% and 4.7% of acute diarrheic episodes (ADE) and non-ADE, respectively. The norovirus incidence was 5.8 infections per 100 child-months. Partial nucleotide sequencing characterized six different norovirus genotypes, with GII.4 Sydney 2012 being detected in 50% associated with three different polymerase genotypes (GII·P31, GII·P16 and GII·P4 New Orleans 2009). FUT3 genotyping was yielded seven new mutations in this population. A significant association between symptomatic norovirus infection and secretor profile could be inferred.

Systematic sequence analysis of the FUT3 gene identifies 11 novel alleles in the Sindhi and Punjabi populations from Pakistan

The FUT3 (Lewis) gene is responsible for the expression of Lewis fucosyltransferase, which is required for the synthesis of the structural determinants of both Lewis^a and Lewis^b specificity. These factors play an important role not only in clinical but also in medico-legal investigations. The gene sequence is highly polymorphic and ethnically specific. In the current study, we performed systematic sequence analysis of the coding region of FUT3 by DNA sequencing to investigate the genetic variations of FUT3 and the molecular basis of the Lewis phenotype in the Sindhi and Punjabi populations of Pakistan. Twenty-three point mutations were observed, including 7 unreported mutations, among which two missense mutations (490 G > A and 959 T > C) were predicted to be deleterious to enzyme activity by software assessment. In total, we observed 24 Lewis alleles, including 11 novel ones. However, all unreported missense mutations were present in Lewis-negative alleles confirmed previously. According to genotypic data, the Lewis-negative phenotypic frequencies were 11.5% and 22.93% in the Sindhi and Punjabi ethnic groups, respectively. Moreover, we found that le^202,314 and le^59,1067 were predominant among Lewis-negative alleles, while the frequency of le^59,1067 in the Punjabi population was significantly higher than that in the Sindhi population. In summary, our study revealed that there is a relatively high degree of sequence variation of the Lewis gene in Pakistani populations and provided the first genetic data on FUT3 in these two ethnic groups from Pakistan. The allele types and their frequencies showed that these ethnic groups exhibit more Caucasian components.

Molecular epidemiology and host genetics of norovirus and rotavirus infections in Portuguese elderly living in aged care homes

Norovirus (NoV) and rotavirus group A (RVA) are major agents of acute gastroenteritis worldwide. This study aimed to investigate their epidemiological profile in Portuguese elderly living in long-term care facilities and to assess the host genetic factors mediating infection susceptibility. From November 2013 to June 2015, 636 faecal specimens from 169 elderly, mainly asymptomatic, living in nursing homes in Greater Lisbon and Faro district, Portugal, were collected. NoV and RVA were detected by real-time polymerase chain reaction and NoV genotyped by phylogenetic analysis. NoV detection rate was 7.1% (12 of 169). Three GI.3 and one GII.6 strains were genotyped. RVA detection rate was 3.6% (6 of 169), exclusively in asymptomatic individuals. Host genetic factors associated with infection susceptibility were described on 250 samples by saliva-based enzyme-linked immunosorbent assays. The Lewis-negative phenotype was 8.8% (22 of 250) and the rate of nonsecretors was 16.8% (42 of 250). Association to NoV and RVA infection was performed in the subgroup of individuals (n = 147) who delivered both faecal and saliva samples. The majority of NoV- and RVA-positive individuals (90.9% and 83.3%, respectively) were secretor-positive, with Lewis B phenotype. In a subset of individuals, FUT2 and FUT3 genes were genotyped to assess mutations and validate the secretor and Lewis phenotypes. All sequenced nonsecretors were homozygous for FUT2 nonsense mutation G428A. In this study, low detection rates of NoV and RVA infections were found during two winter seasons. However, even in the absence of any outbreak, the importance of finding these infections in a nonepidemic situation in long-term care facilities may have important implications for infection control.

Regional variations in human milk oligosaccharides in Vietnam suggest FucTx activity besides FucT2 and FucT3

Breastfeeding is the normal way of providing young infants with the nutrients they need for healthy growth and development (WHO). Human milk oligosaccharides (hMOS) constitute a highly important class of nutrients that are attracting strong attention in recent years. Several studies have indicated that hMOS have prebiotic properties, but also are effective in anti-adhesion of pathogens, modulating the immune system and providing nutrients for brain growth and development. Most of the latter functions seem to be linked to the presence of fucose-containing immunodeterminant epitopes, and Neu5Ac-bearing oligosaccharides. Analysis of hMOS isolated from 101 mothers’ milk showed regional variation in Lewis- and Secretor based immunodeterminants. Lewis-negative milk groups could be sub-divided into two sub-groups, based on the activity of a third and hitherto unidentified fucosyltransferase enzyme. Analysis of hMOS remaining in faeces showed three sub-groups based on hMOS surviving passage through the gut, full consumption, specific partial consumption and non-specific partial consumption, fitting previous findings.

Genomic coordinates and continental distribution of 120 blood group variants reported by the 1000 Genomes Project

BACKGROUND

The 1000 Genomes Project provides a database of genomic variants from whole genome sequencing of 2504 individuals across five continental superpopulations. This database can enrich our background knowledge of worldwide blood group variant geographic distribution and identify novel variants of potential clinical significance.

STUDY DESIGN AND METHODS

The 1000 Genomes database was analyzed to 1) expand knowledge about continental distributions of known blood group variants, 2) identify novel variants with antigenic potential and their geographic association, and 3) establish a baseline scaffold of chromosomal coordinates to translate next-generation sequencing output files into a predicted red blood cell (RBC) phenotype.

RESULTS

Forty-two genes were investigated. A total of 604 known variants were mapped to the GRCh37 assembly; 120 of these were reported by 1000 Genomes in at least one superpopulation. All queried variants, including the ACKR1 promoter silencing mutation, are located within exon pull-down boundaries. The analysis yielded 41 novel population distributions for 34 known variants, as well as 12 novel blood group variants that warrant further validation and study. Four prediction algorithms collectively flagged 79 of 109 (72%) known antigenic or enzymatically detrimental blood group variants, while 4 of 12 variants that do not result in an altered RBC phenotype were flagged as deleterious.

CONCLUSION

Next-generation sequencing has known potential for high-throughput and extended RBC phenotype prediction; a database of GRCh37 and GRCh38 chromosomal coordinates for 120 worldwide blood group variants is provided as a basis for this clinical application.

Distribution of Lewis and Secretor polymorphisms and corresponding CA19-9 antigen expression in a Chinese population

The Lewis (FUT3) and Secretor (FUT2) genes, corresponding to secretion of Lewis ABO (H) histo‐blood group antigen CA19‐9, are highly polymorphic with differences between populations. In this study, the FUT3 and FUT2 genes in 316 Chinese participants were sequenced to detect polymorphisms, and the associated CA19‐9 antigen secretion was also measured. In total, 14 genotypes of FUT3 and 10 genotypes of FUT2 were verified. Le/Le, Le/le^59,508 and Le/le⁵⁹ were the main genotypes of FUT3 with frequencies of 53.2%, 10.7% and 3.5%, respectively. Se/Se, Se/se³⁸⁵ and se³⁸⁵/se³⁸⁵ were the main genotypes of FUT2, with frequencies of 21.4%, 18.6% and 16.2%, respectively. The alleles le¹⁰⁶⁷ and le⁵⁰⁸ were found extensively in the Chinese population, and the frequency of allele se³⁸⁵ was shown to be higher than previously reported. Phenotype analysis revealed that 9.8% of individuals were the Lewis‐negative type and 22.5% were the secretor‐negative type. Combined phenotypes showed that 3.2% of participants were of ‘double‐negative’ phenotype (le, se) and 19.3% were of single dominant non‐secretor phenotype (Le, se). Serum Lewis antigen CA19‐9 levels were significantly different between subgroups and consistent with the defined phenotype. Our study revealed the unique distribution of Lewis and Secretor polymorphisms in a large Chinese population, and decoded the combined genotypes of the two CA19‐9‐related genes.

Blood Groups in Infection and Host Susceptibility

Blood group antigens represent polymorphic traits inherited among individuals and populations. At present, there are 34 recognized human blood groups and hundreds of individual blood group antigens and alleles. Differences in blood group antigen expression can increase or decrease host susceptibility to many infections. Blood groups can play a direct role in infection by serving as receptors and/or coreceptors for microorganisms, parasites, and viruses. In addition, many blood group antigens facilitate intracellular uptake, signal transduction, or adhesion through the organization of membrane microdomains. Several blood groups can modify the innate immune response to infection. Several distinct phenotypes associated with increased host resistance to malaria are overrepresented in populations living in areas where malaria is endemic, as a result of evolutionary pressures. Microorganisms can also stimulate antibodies against blood group antigens, including ABO, T, and Kell. Finally, there is a symbiotic relationship between blood group expression and maturation of the gastrointestinal microbiome.

The Blood Group A Genotype Determines the Level of Expression of the Blood Group A on Platelets But Not the Anti-B Isotiter

BACKGROUND

The extent of expression of the blood group A on platelets is controversial. Further, the relation between platelets' blood group A expression and the titers of isoagglutinins has not been thoroughly investigated, so far.

METHODS

We evaluated the relation between the genotype with platelets' blood group A and H expression estimated by flow cytometry and the titers of isoagglutinins.

RESULTS

The A expression varied between genotypes and within genotypes. However, the expression in A1 was stronger than in all other genotypes (p < 0.0001). An overlap of expression levels was apparent between homozygous A1A1 and heterozygous A1 individuals. Still, The A1A1 genotype is associated with a particularly high antigen expression (p = 0.009). Platelets' A expression in A2 versus blood group O donors was also significant (p = 0.007), but there was again an overlap of expression. The secretor status had only little influence on the expression (p = 0.18). Also, isoagglutinin titers were not associated with genotypes.

CONCLUSION

To distinguish between A1 and A2 donors may reduce incompatible platelet transfusions and therefore be favorable on platelet transfusion increment. Clinical data are needed to support this notion.

The relationship between Lewis/Secretor genotypes and serum carbohydrate antigen 19-9 levels in a Korean population

BACKGROUND

The Lewis histo-blood group system consists of 2 major antigens-Lea and Leb-and a sialyl Lewis antigen-carbohydrate antigen (CA) 19-9. We investigated the distribution of Lewis genotypes and evaluated the relationship between the Lewis/Secretor genotypes and the serum level of CA 19-9 in a Korean population to identify whether the serum CA 19-9 levels are influenced by the Lewis/Secretor genotypes.

METHODS

The study included 242 individuals who had no malignancies. Lewis genotyping was performed for the 59T>G, 508G>A and 1067T>A polymorphic sites. The Secretor genotype was determined through analysis of the 357C>T and 385A>T polymorphic sites and the fusion gene. Serum CA 19-9 level was analyzed using an electrochemiluminescence immunoassay.

RESULTS

Individuals carrying the 3 common genotypes-Le/Le, Le/le(59,508), and Le/le(59,1067)-accounted for 95% of the study population. In the Korean population, the allelic frequencies of Le, Le(59), le(59,508), and le(59,1067) were 0.731, 0.010, 0.223, and 0.035, respectively. We found a significant difference in serum CA 19-9 concentrations among the 9 Lewis/Secretor genotype groups (P<0.001). The serum CA 19-9 levels in subjects with genotype groups 1 and 2 (Le/- and se/se) were higher than those with genotype groups 3-6 (Le/- and Se/-; 15.63 vs 6.64 kU/L, P<0.001).

CONCLUSIONS

Le/Le, Le/le(59,508), and Le/le(59,1067) are frequent Lewis genotypes in Koreans. Because serum CA 19-9 levels are significantly influenced by the Lewis/Secretor genotypes, caution is suggested when interpreting the serum CA 19-9 levels.

Identification of 14 new alleles at the fucosyltransferase 1, 2, and 3 loci in Styrian blood donors, Austria

BACKGROUND

Genes for fucosyltransferases 1 (FUT1:H), 2 (FUT2:Secretor), and 3 (FUT3:Lewis) encode enzymes crucial for ABH and Lewis blood group antigen synthesis. They are highly polymorphic and ethnically and geographically specific.

STUDY DESIGN AND METHODS

Genetic variations and allele frequencies of FUT1, FUT2, and FUT3 encoding regions and flanking sequences were analyzed in 100 Styrian blood donors by systematic sequencing. Haplotypes were verified with sequence-specific primers. To identify discrepancies, serologically determined ABO and Lewis blood groups were correlated to respective genotypes.

RESULTS

Two novel FUT1 alleles were defined by 9C>T (silent) and 991C>A (P331T) mutations, the latter located in the catalytic domain of the enzyme. Five new alleles of FUT2 were found: three were characterized by new variants and two resulted from new combinations of known polymorphisms. The new 412G>A (G138S) mutation also is located in the catalytic domain. A new nonsecretor allele, based on the presence of 428G>A (nonsense), was found. Another FUT2 allele may have resulted from an intragenic crossover event. FUT3 analysis revealed seven novel alleles, partly based on the new mutations 41G>A (R14H), 1060C>G (R354G), 735G>C (silent), and 882C>T (silent). While 41G>A is placed in the cytoplasmic domain and functional, 1060C>G is placed in the catalytic domain.

CONCLUSION

Multiple common and sporadic sequence variations including 14 new alleles at FUT1, FUT2, and FUT3 loci were identified. Four novel mutations result in amino acid substitution in the protein. Three of them are predicted to have adverse effects on the enzyme activity. A novel nonsecretor allele was found.

Histo-blood group gene polymorphisms as potential genetic modifiers of infection and cystic fibrosis lung disease severity

BACKGROUND

The pulmonary phenotype in cystic fibrosis (CF) is variable; thus, environmental and genetic factors likely contribute to clinical heterogeneity. We hypothesized that genetically determined ABO histo-blood group antigen (ABH) differences in glycosylation may lead to differences in microbial binding by airway mucus, and thus predispose to early lung infection and more severe lung disease in a subset of patients with CF.

METHODS AND PRINCIPAL FINDINGS

Clinical information and DNA was collected on >800 patients with the DeltaF508/DeltaF508 genotype. Patients in the most severe and mildest quartiles for lung phenotype were enrolled. Blood samples underwent lymphocyte transformation and DNA extraction using standard methods. PCR and sequencing were performed using standard techniques to identify the 9 SNPs required to determine ABO blood type, and to identify the four SNPs that account for 90-95% of Lewis status in Caucasians. Allele identification of the one nonsynonymous SNP in FUT2 that accounts for >95% of the incidence of nonsecretor phenotype in Caucasians was completed using an ABI Taqman assay. The overall prevalence of ABO types, and of FUT2 (secretor) and FUT 3 (Lewis) alleles was consistent with that found in the Caucasian population. There was no difference in distribution of ABH type in the severe versus mild patients, or the age of onset of Pseudomonas aeruginosa infection in the severe or mild groups. Multivariate analyses of other clinical phenotypes, including gender, asthma, and meconium ileus demonstrated no differences between groups based on ABH type.

CONCLUSIONS AND SIGNIFICANCE

Polymorphisms in the genes encoding ABO blood type, secretor or Lewis genotypes were not shown to associate with severity of CF lung disease, or age of onset of P. aeruginosa infection, nor was there any association with other clinical phenotypes in a group of 808 patients homozygous for the DeltaF508 mutation.

Extremely high prevalence ofDNASE1*1 allele in African populations

The single nucleotide polymorphism (SNP) at deoxyribonuclease I (DNase I), designated as DNASE1 (NCBI SNP number; 1053874), in exon 8 (A2317G) has been shown to be associated with liver disease, colorectal carcinoma, and gastric carcinoma in Japanese patients. In this study, we investigated the frequency of the DNASE1 polymorphism in Ghanaian (n = 96) and Xhosa (n = 78) populations and compared the results with those of other studies. The single nucleotide polymorphism was detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. The frequencies of DNASE1*1 in the Ghanaian and Xhosa populations were 0.90 and 0.88, respectively. These two African populations had an extremely high frequency of DNASE1*1, similar to that of the Ovambos living in Namibia. Caucasians and Asians had a lower frequency of DNASE1*1 than the African groups. This study is the first to reveal an extremely high frequency of DNASE1*1 among African populations.

Molecular mechanisms of Lewis antigen expression

Lewis antigens comprise type 1 (Lewis a, Lewis b) and type 2 (Lewis X, Lewis Y) carbohydrates. Lewis X and Lewis Y are regarded as tumor-associated markers, and some of these antigens and their derivatives interact with selectins, mediating cell-to-cell adhesion. In addition, Lewis b on the gastric epithelial surface has been identified as an acceptor for attachment of Helicobacter pylori. In this review, we describe the regulation the expression of type 1 Lewis antigens on erythrocytes or digestive organs by two genes (FUT2 and FUT3), and the ethnic specificity of the polymorphism of these genes for forensic use.

Population differences in DNA sequence variation and linkage disequilibrium at the PON1 gene

Polymorphisms of the promoter region (-108C/T) and the coding region (192Q/R) of the paraoxonase 1 gene (PON1) showed differences in association with cardiovascular disease risk in various populations. To characterize the genetic variation underlying these important polymorphisms, we examined DNA sequence variation both in a 1.3-kb promoter region 16.5 kb from codon 192, and in a 1.7-kb region centered on the 192Q/R polymorphic site of the coding region of PON1, in 30 Africans, 30 Europeans and 64 Japanese. We found 10 polymorphic sites and 11 haplotypes in the 1.3-kb promoter region and 10 biallelic polymorphic sites and 10 haplotypes in the 1.7-kb region. From the PON1 sequences of chimpanzees and an orangutan, the ancestral type of codon 192 was found to be R. The number of pairs of polymorphic sites between the promoter and 1.7-kb regions that were in significant linkage disequilibrium was much higher in a Japanese population than in African and European populations. In addition, the pairs of polymorphic sites in linkage disequilibrium differed among the three populations. These results suggest that some of the population differences in association with risk for coronary heart disease can be explained by population differences in haplotype frequency of PON1 haplotypes.

Lewis enzyme (alpha1-3/4 fucosyltransferase) polymorphisms do not explain the Lewis phenotype in the gastric mucosa of a Portuguese population

The human alpha-1,3/4 fucosyltransferase III (FucT III) catalyses the synthesis of Lewis antigens including Le(b) antigen which is a ligand for Helicobacter pylori adhesion. Several polymorphisms have been described in the FUT3 gene affecting both the transmembrane and catalytic domains, some of which affect the enzyme activity. The aim of the present work was to study the Lewis gene polymorphisms in a Caucasian Portuguese population, with a high rate of H. pylori infection, and to evaluate the implications of mutant enzymes in Le(b) expression in the gastric mucosa. We studied 460 asymptomatic or dyspeptic individuals from northern Portugal. Screening for Lewis gene polymorphisms was performed by SSCP and direct sequencing. Lewis phenotype in gastric mucosa was determined by immunohistochemistry. In 47 individuals with a Lewis negative blood group, we found FUT3 gene polymorphisms that were previously described in other populations: 59T>G, 202T>C, 314C>T, 508G>A and 1067T>A. Among the 47 Lewis negative individuals in blood, only nine were also negative in gastric mucosa, suggesting the existence of another alpha 1-4 fucosyltransferase that is responsible for Le(a) and Le(b) synthesis in gastric mucosa.

Alpha1,4-fucosyltransferase activity: a significant function in the primate lineage has appeared twice independently

In the animal kingdom the enzymes that catalyze the formation of alpha1,4 fucosylated-glycoconjugates are known only in apes (chimpanzee) and humans. They are encoded by FUT3 and FUT5 genes, two members of the Lewis FUT5-FUT3-FUT6 gene cluster, which had originated by duplications of an alpha3 ancestor gene. In order to explore more precisely the emergence of the alpha1,4 fucosylation, new Lewis-like fucosyltransferase genes were studied in species belonging to the three main primate groups. Two Lewis-like genes were found in brown and ruffed lemurs (prosimians) as well as in squirrel monkey (New World monkey). In the latter, one gene encodes an enzyme which transfers fucose only in alpha1,3 linkage, whereas the other is a pseudogene. Three genes homologous to chimpanzee and human Lewis genes were identified in rhesus macaque (Old World monkey), and only one encodes an alpha3/4-fucosyltransferase. The ability of new primate enzymes to transfer fucose in alpha1,3 or alpha1,3/4 linkage confirms that the amino acid R or W in the acceptor-binding motif "HH(R/W)(D/E)" is required for the type 1/type 2 acceptor specificity. Expression of rhesus macaque genes proved that fucose transfer in alpha1,4 linkage is not restricted to the hominoid family and may be extended to other Old World monkeys. Moreover, the presence of only one enzyme supporting the alpha1,4 fucosylation in rhesus macaque versus two enzymes in hominoids suggests that this function occurred twice independently during primate evolution.

Three-base deletion and one-base insertion of the alpha(1,4)galactosyltransferase gene responsible for the P phenotype

BACKGROUND

Recently, an alpha(1,4)galactosyltransferase gene that is responsible for synthesis of P(k) (Gb3) was isolated. The P individuals who did not express the P(k), P, and P(1) antigens on RBC membranes were shown to lack the P(k) (Gb3) synthase activity because of multiple distinct mutations in the alpha(1,4)galactosyltransferase gene.

STUDY DESIGN AND METHODS

DNA sequences of the P(k) (Gb3) synthase gene in three Japanese individuals with the p phenotype were analyzed.

RESULTS

One individual was found to be homozygous for an allele containing a three-base deletion of CTTCTTC to CTTC from bases 237 through 243 in the coding region. The other two individuals were found to be homozygous for an allele containing a single cytosine insertion in a cytosine repeat at positions 1026 through 1029, resulting in a reading frame shift.

CONCLUSION

The P blood group phenotype is due to several distinct nonfunctional alleles without any predominant allele.

Fucosyltransferases: structure/function studies

Alpha3-fucosyltransferases (alpha3-FucTs) catalyze the final step in the synthesis of a range of important glycoconjugates that function in cell adhesion and lymphocyte recirculation. Six members of this family of enzymes have been cloned from the human genome, and their expression pattern has been shown to be highly regulated. Each enzyme has a unique acceptor substrate binding pattern, and each generates a unique range of fucosylated products. Results from a range of studies have provided information on amino acids in the FucT sequence that contribute to the differential acceptor specificity for the FucTs, and to the binding of the nucleotide sugar donor GDP-fucose. These results, in conjunction with results obtained from the analysis of the disulfide bond pattern, have provided useful clues about the spatial distribution of amino acids that influence or directly contribute to substrate binding. This information is reviewed here, and a molecular fold prediction is presented which has been constructed based on the available information and current modeling methodology.

Identification of a missense mutation (G329A;Arg(110)--> GLN) in the human FUT7 gene

The human FUT7 gene codes for the alpha1,3-fucosyltransferase VII (Fuc-TVII), which is involved in the biosynthesis of the sialyl Lewis x (SLe(x)) epitope on human leukocytes. The FUT7 gene has so far been considered to be monomorphic. Neutrophils isolated from patients with ulcerative colitis were examined for apparent alterations in protein glycosylation patterns by Western blot analysis using monoclonal antibodies directed against SLe(x) and SLe(x)-related epitopes. One individual showed lower levels of SLe(x) expression and an elevated expression of CD65s compared to controls. The coding regions of the FUT7 gene from this individual were cloned, and a G329A point mutation (Arg(110) --> Gln) was found in one allele, whereas the other FUT7 allele was wild type. No Fuc-TVII enzyme activity was detected in COS-7 cells transiently transfected with the mutated FUT7 construct. The FUT7 Arg(110) is conserved in all previously cloned vertebrate alpha 1,3-fucosyltransferases. Polymerase chain reaction followed by restriction enzyme cleavage was used to screen 364 unselected Caucasians for the G329A mutation, and a frequency of < or =1% for this mutation was found (3 heterozygotes). Genetic characterization of the family members of one of the additional heterozygotes identified one individual carrying the G329A mutation in both FUT7 alleles. Peripheral blood neutrophils of this homozygously mutated individual showed a lowered expression of SLe(x) and an elevated expression of CD65s when analyzed by Western blot and flow cytometry. The homozygous individual was diagnosed with ulcer disease, non-insulin-dependent diabetes, osteoporosis, spondyloarthrosis, and Sjögren's syndrome but had no history of recurrent bacterial infections or leukocytosis.

The polymorphisms of fucosyltransferases

The alpha(1,2)fucosyltransferase Se enzyme regulates the expression of the ABH antigens in secretion. Secretors, who have ABH antigens in their saliva, have at least one functional Se allele in the FUT2 locus, while non-secretors, who fail to express ABH antigens in saliva, are homozygous for the non-functional se allele. Molecular analyses of the FUT2 polymorphism of various populations have indicated the ethnic specificity of null alleles: the null allele se(428) is a common Se enzyme-deficient allele in Africans and Caucasians but does not occur in Asians, whereas the null allele se(357,385) is specific to Asians. The gene frequency of se(428) or se(357,385) is about 0.5 in each respective population. Why the se(428) is absent in Asians is of interest. Also here, we describe the polymorphisms of the fucosyltransferase genes (FUT1, FUT3 and FUT6).

Genetic background of Lewis negative blood group phenotype and its association with atherosclerotic disease in the NHLBI family heart study

OBJECTIVES

To examine the prevalence of four mutations, T59G, T1067A, T202C and C314T, of the human alpha(1,3/1,4) fucosyltransferase 3 (FUT 3) gene amongst persons with Lewis negative and those with Lewis positive blood group phenotype. An additional objective was to explore the hypothesis that these mutations are associated with coronary heart disease and inflammatory reaction.

DESIGN

A population-based cross-sectional study.

SETTING

Analysis of samples and data from the National Heart Lung and Blood Institute Family Heart Study.

SUBJECTS

All Lewis (a-b-) participants (n = 136) and a sample of Lewis positive participants (n = 136) of the Family Heart Study; all were of Caucasian ethnicity.

MAIN OUTCOME MEASURES

The prevalence of examined mutations by Lewis phenotype.

RESULTS

The examined mutations were common and strongly associated with the Lewis (a-b-) phenotype. Accordingly, 90-95% of Lewis (a-b-) individuals amongst Caucasians can be identified by screening for these four mutations. Exploratory analyses suggested that with the exception of T59G, all examined mutations were positively associated with prevalent coronary heart disease, although not statistically significantly, perhaps due to the small number of prevalent coronary heart disease cases. C-reactive protein tended to be higher amongst persons with a TC or CC genotype at position 202 (3.07 +/- 0.41 vs. 2.08 +/- 0.32 mg L-1, P = 0.06).

CONCLUSIONS

Four specific mutations of fucosyltransferase 3 gene are responsible for the vast majority of Lewis (a-b-) phenotypes in Caucasians. These mutations are common in the population at large and may be associated with increased risk of coronary heart disease. Further studies using larger samples are warranted.

Simple PCR detection of haptoglobin gene deletion in anhaptoglobinemic patients with antihaptoglobin antibody that causes anaphylactic transfusion reactions

Two anhaptoglobinemic patients showing anaphylactic transfusion reactions by antihaptoglobin antibody were found. Southern blot analysis indicated that 2 patients were homozygous for the deleted allele of the haptoglobin gene (Hpdel) as reported previously. We have identified the junction region of the deletion from genomic DNA of 1 patient using cassette-mediated polymerase chain reaction (PCR). Then, the deleted region from the 5′ breakpoint to the promoter region of the Hpwas amplified from genomic DNA of a control individual using PCR. DNA sequence analysis of these regions indicated that the 5′ breakpoint of the Hpdel allele was located 5.2 kilobase (kb) upstream of exon 1 of the Hp and the 3′ breakpoint was positioned between 52 and 53 base pair (bp) upstream of exon 5 of the haptoglobin-related gene. There was no significant homology between the DNA sequences flanking the 5′ and 3′ breakpoints, except for a 2-bp (TG) identity. To examine the gene frequency, we have developed a simple PCR method to detect the gene deletion. We found 8, 16, and 17 Hpdelalleles in 157 Koreans, 523 Japanese, and in 284 Chinese, respectively, but did not find the Hpdel in 101 Africans or in 100 European-Africans. The incidence of individuals homozygous for the Hpdel allele was therefore expected to be 1/4000 in Japanese, 1/1500 in Koreans, and 1/1000 in Chinese. This incidence is higher than that of IgA deficiency in Japanese. More attention should be paid on haptoglobin deficiency and antihaptoglobin antibody as the cause of transfusion-related anaphylactic reactions in Asian populations.

Significance of each of three missense mutations, G484A, G667A, and G808A, present in an inactive allele of the human Lewis gene (FUT3) for alpha(1,3/1,4)fucosyltransferase inactivation

Recently, we found three novel missense mutations, G484A (Asp162Asn), G667A (Gly223Arg), and G808A (Val270Met), present in a Lewis-negative allele (le484,667,808) from an African (Xhosa) population. To define the relative contribution of each of the three mutations in the le484,667,808 allele for inactivation of the FUT3-encoded enzyme, we made chimeric FUT3 containing each of the three mutations. A transient expression study indicated that COS7 cells transfected with the FUT3 construct containing the G484A mutation expressed the Lewis antigen and had about 20% enzyme activity as compared with COS7 cells transfected with the wild type FUT3 allele, whereas COS7 cells transfected with the FUT3 construct containing either the G667A mutation or the G808A mutation did not express the Lewis antigen and showed no detectable alpha(1,3/1,4)fucosyltransferase activity. These results suggest that the G667A and/or the G808A missense mutations of FUT3 alleles are responsible for the inactivation of the FUT3-encoded enzyme.