Influence of Lewis alpha1-3/4-L-fucosyltransferase (FUT3) gene mutations on enzyme activity, erythrocyte phenotyping, and circulating tumor marker sialyl-Lewis a levels.
Fucosylated glycoproteins carrying alpha1-4 fucose residues are of importance for cell adhesion and as tumor markers. The Lewis gene, FUT3, encodes the only known alpha1-4-fucosyltransferase (FucT), and individuals who are deficient in this enzyme type as Lewis-negative on erythrocytes. We examined the mutational spectrum of the Lewis gene in Denmark and found 6 different mutations. Five, T59G, T202C, C314T, G508A, and T1067A, were frequent, and one, C445A, was only detected in one out of 40 individuals. Allele-specific polymerase chain reaction as well as cloning of FUT3 alleles showed that the 202 and 314 mutations were co-located on the same allele. COS7 cells transfected with an allele having the 202/314 mutations lacked enzyme activity. Polymerase chain reaction-cleavage assays were established for the genotyping of healthy individuals as well as 20 genuine Lewis-negative cancer patients and 10 non-genuine. The latter have Lewis-negative erythrocytes but saliva alpha1-4FucT activity. The genuine Lewis-negative individuals had mutations on both FUT3 alleles. In 66 healthy individuals, a gene dosage effect was detected as FUT3 heterozygous individuals had a lower alpha1-4FucT activity in saliva than did homozygous wild-type individuals. The lower enzyme level in heterozygous individuals resulted in a significantly (p < 0.04) lower level of circulating sialyl-Lewis a structure in serum. This has the clinical impact that cut-off levels in tumor marker assays should be defined on the basis of genotyping. In the group of non-genuine Lewis-negative cancer patients, whose erythrocytes convert from Lewis-positive to Lewis-negative during the disease, FUT3 heterozygosity was significantly (p < 0.05) more common.
Orntoft
T F
TF
Department of Clinical Biochemistry, Skejby University Hospital, DK 8200 Aarhus N, Denmark.
Vestergaard
E M
EM
Holmes
E
E
Jakobsen
J S
JS
Grunnet
N
N
Mortensen
M
M
Johnson
P
P
Bross
P
P
Gregersen
N
N
Skorstengaard
K
K
Jensen
U B
UB
Bolund
L
L
Wolf
H
H
D000017:ABO Blood-Group System / Q000737:chemistry / Q000235:genetics; D000483:Alleles; D000818:Animals; D015295:Antigens, Tumor-Associated, Carbohydrate / Q000378:metabolism*; D001483:Base Sequence; D015152:Blotting, Northern; D019556:COS Cells; D004912:Erythrocytes / Q000737:chemistry*; D005434:Flow Cytometry; D005647:Fucosyltransferases / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007983:Lewis Blood Group Antigens / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009844:Oligosaccharides / Q000378:metabolism*; D010641:Phenotype; D016133:Polymerase Chain Reaction; D051381:Rats; D011917:Rats, Inbred Lew; D012463:Saliva / Q000737:chemistry; D014162:Transfection
D000017:ABO Blood-Group System; D015295:Antigens, Tumor-Associated, Carbohydrate; D007983:Lewis Blood Group Antigens; D009844:Oligosaccharides; C058981:sialyl-Le(a) oligosaccharide; D005647:Fucosyltransferases; C019818:3-galactosyl-N-acetylglucosaminide 4-alpha-L-fucosyltransferase