H-抗原缺乏分泌型个体FUT1及FUT2等位基因的分子基础

一例H-缺乏分泌型个体被发现。其血清学表现为：红细胞上无A、B、H抗原；唾液中有B、H抗原分泌；血清中检出了抗A抗体。推测其为类孟买OHmB型。在该个体FUT1等位基因编码区上发现两处单碱基突变（T460C、G1042A）。这两个点变异，将导致两个氨基酸的置换（Y154H、E348K）。同时也破坏了限制性内切酶RsaⅠ和AvaⅠ的作用部位。用PCR－RFLP法可检出此两种变异。用PCR－RFLP法证实，该个体为T460C、G1042A变异的纯合子。在136例随机个体中未能查出上述变异。将该FUT1基因转染COS－7细胞未能检出α2－FUT活性及证实H抗原的表达。该个体的FUT2基因与野生型一致。

MOLECULAR BASIS OF FUT1 AND FUT2 FOR H-DEFICIENT SECRETOR TYPE: A PARA-BOMBAY INDIVIDUAL

We have found an H-deficient secretor type individual who expressed B and H antigens in saliva with anti-A activity in his serum, without ABH antigeus on his red blood cells. He was a para Bombay phenotype OBHm as determined by blood group serological method. His FUTt alleles contained two single base changes (T460C and G1042A) in the coding region relative to the wild type allele as determined by the PCR-PFLP. These substitution results in changes in two amino acid residues (Y154H and E348K). The T460C and G1042A mutations destroy endonucleases Rsa Ⅰ and Ava Ⅰ sites, respec-tively. The results indicated that a para-Bombay individual was homozygous for the T460C and G1042A mutations. No such mutation was found in 136 Yandomly-selected Japanese indiviuals.The measurement of the α(1. 2) fucosyltransferase activity after transient expression of the FUT1 al-leles in cos-7 cells indicated that the H-deficient allele-encoded enzyme had no detectable activity. The sequence of the FUT2 allele was the same as the wild type alleles.