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 Galbeta1-4GlcNAcbeta1-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 (h(a), 547similar to548 AG-del; h(b), 880similar to881 TT-del; h(c), R220C; h(d), R220H; h(e), F174L; and h(f), N327T) were observed. Two h alleles, h(e) and h(f), 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 h(f) allele has missense mutation of nucleotide 980A>C, predicting the amino acid 327 substitution of Asn to Thr. Frequencies of the 6 alleles are h(a) 46.67%, h(b) 38.33%, h(c) 5.00%, h(d) 1.67%, h(e) 3.33%, and h(f) 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.