Analyses of polymorphisms in the FUT2 and FUT3 and mechanism of synthesis of Lewis blood group antigens

我们在Ovambos、突厥人和蒙古人的FUT2编码区发现了24个包含7个新snp（其中3个是失活突变）的snp。在这些人群中观察到的遗传变异与邻近人群相似，似乎反映了人类迁徙的地理背景和历史。在筛选se^<fus>时，在蒙古样本中鉴定出Sec1-FUT2-Sec1杂交等位基因。这一结果提示我们在选择PCR引物时要谨慎，否则会因为重组等位基因而导致se^<fus>的假阳性分型，而这种等位基因是罕见的。通过分析FUT2的启动子区域，我们发现非洲特异性snp发生率高，影响培养细胞的转录活性。在非洲种群和上游区域中，包含该区域的长链不平衡（LD）块也可能作为一个独立的编码区块进行平衡选择。为了阐明调节Lewis抗原合成的Lewis酶和Se酶在高尔基体中的位置，我们构建了嵌合基因FUT23和FUT32，它们交换了FUT2和FUT3的n端细胞质区域。我们观察到，与FUT2和FUT3相比，les ^a抗原在FUT23和FUT32的COS-7转染上的表达高于Le^b抗原。这一观察结果表明，这两种酶的定位对于Lewis抗原的表达是重要的，并且细胞质结构域包含这一信号。我们正在研究由融合蛋白与荧光蛋白编码的酶的亚细胞定位以及FUT3编码区域在几种人群中的变化。

We identified 24 SNPs containing seven novel SNPs (three of them are inactivating mutations) in the coding region of the FUT2 in Ovambos, Turks, and Mongolian populations. The genetic variations observed in these populations were similar to that of neighboring ones and seemed to reflect the geographic background and history of human migration. During screening of the se^<fus>, a Sec1-FUT2-Sec1 hybrid allele was identified in a Mongolian sample. This result implies that we need to be careful in choosing PCR primers otherwise make false-positive typing of se^<fus> because of recombinant alleles, while this allele is rare. By analysis the promoter region of the FUT2, we found African-specific SNPs with high incidence that affected transcriptional activity in culture cells. It is possible that long linkage disequilibrium (LD) block containing this region in African populations and the upstream region is also under balancing selection as an independent block of coding region.To elucidate the location of the Lewis and Se enzymes that regulate the synthesis of Lewis antigens in Golgi apparatus, we constructed chimeric genes, FUT23 and FUT32 that exchanged the N-terminal cytoplasmic regions of the FUT2 and FUT3. We observed higher expression of the Le^a than that of Le^b antigens on the COS-7 transfectants of FUT23 and FUT32 comparing to which of FUT2 and FUT3. This observation suggests that the localization of two enzymes is important for the expression of the Lewis antigens and the cytoplasmic domains contain the signal of that. We are under investigation of subcellular localization of the enzymes encoded by the fusion proteins with fluorescent proteins and the variations of the coding region of the FUT3 in several human populations.