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

α(1,2)-Fucosyltransferase catalyzes the transfer of fucose to the C-2 position of galactose on type II precursor substrate Galβ1-4GlcNAcβ1- 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 α(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 α(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, 547-548 AG-del; h^b, 880-881 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 h^e 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^e 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 h^a and h^b, 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.