Nishihara S, Narimatsu H, Iwasaki H, Yazawa S, Akamatsu S, Ando T, Seno T, Narimatsu I
Division of Cell Biology, Soka University, Tokyo, Japan.
J Biol Chem. 1994 Nov 18;269(46):29271-8.
The expression of Lewis histo-blood group antigen is determined by the Lewis type alpha(1,3/1,4) fucosyltransferase encoded in Fuc-TIII gene (Le gene) on chromosome 19. Weak hemagglutination reactions are often observed in the Lewis blood typing to cause false-negative reactions. The level of CA19-9 tumor marker, defined as sialylated Le(a) (sLe(a)), is influenced by the Lewis blood phenotype. The sLe(a) antigen is also considered to play a role in hematogenous metastasis of tumor cells. The accurate genotyping of Fuc-TIII gene would be, therefore, necessary for solving above questions. In addition to the two missense mutations previously reported by us, i.e. the T59G and the G508A, further sequence analyses revealed a new single base substitution, the T1067A, changing the Ile356 to Lys in the catalytic region. Polymerase chain reaction-restriction fragment length polymorphism methods were developed for the detection of these three missense mutations and applied in 15 Lewis negative (le/le) and 65 Lewis positive individuals (Le/Le or Le/le). These methods were found to be useful for genetic diagnosis for the Lewis histo-blood typing. All le alleles had the T59G mutation, whereas none of the Le alleles did. The le alleles were divided in two types, le1, having the G508A mutation, and le2, having the T1067A mutation. The T1067A mutation reduced the enzyme activity less than 10%, whereas the G508A mutation in the catalytic domain made the enzyme completely inactive. The frequency of occurrence of Le, le1, and le2 in the Japanese population by random sampling study was found to be 66, 30, and 4%, respectively.
Lewis组织血型抗原的表达由位于19号染色体上Fuc-TIII基因（Le基因）编码的Lewis型α(1,3/1,4)岩藻糖基转移酶决定。在Lewis血型分型中常观察到弱血凝反应，导致假阴性反应。CA19-9肿瘤标志物水平，即唾液酸化Le(a)（sLe(a)），受Lewis血型表型影响。sLe(a)抗原也被认为在肿瘤细胞的血行转移中起作用。因此，为解决上述问题，Fuc-TIII基因的准确基因分型是必要的。除了我们之前报道的两个错义突变，即T59G和G508A，进一步的序列分析发现了一个新的单碱基替换，T1067A，该突变在催化区域将Ile356变为Lys。开发了聚合酶链反应-限制性片段长度多态性方法来检测这三个错义突变，并应用于15名Lewis阴性（le/le）和65名Lewis阳性个体（Le/Le或Le/le）。发现这些方法对Lewis组织血型分型的基因诊断有用。所有le等位基因都有T59G突变，而Le等位基因均无此突变。le等位基因分为两种类型，le1有G508A突变，le2有T1067A突变。T1067A突变使酶活性降低不到10%，而催化结构域中的G508A突变使酶完全失活。通过随机抽样研究发现，日本人群中Le、le1和le2的出现频率分别为66%、30%和4%。
