Systematic sequence analysis of the FUT3 gene identifies 11 novel alleles in the Sindhi and Punjabi populations from Pakistan

The FUT3 (Lewis) gene is responsible for the expression of Lewis fucosyltransferase, which is required for the synthesis of the structural determinants of both Lewis(a) and Lewis(b) specificity. These factors play an important role not only in clinical but also in medico-legal investigations. The gene sequence is highly polymorphic and ethnically specific. In the current study, we performed systematic sequence analysis of the coding region of FUT3 by DNA sequencing to investigate the genetic variations of FUT3 and the molecular basis of the Lewis phenotype in the Sindhi and Punjabi populations of Pakistan. Twenty-three point mutations were observed, including 7 unreported mutations, among which two missense mutations (490 G > A and 959 T > C) were predicted to be deleterious to enzyme activity by software assessment. In total, we observed 24 Lewis alleles, including 11 novel ones. However, all unreported missense mutations were present in Lewis-negative alleles confirmed previously. According to genotypic data, the Lewis-negative phenotypic frequencies were 11.5% and 22.93% in the Sindhi and Punjabi ethnic groups, respectively. Moreover, we found that le(202,314) and le(59,1067) were predominant among Lewis-negative alleles, while the frequency of le(59,1067) in the Punjabi population was significantly higher than that in the Sindhi population. In summary, our study revealed that there is a relatively high degree of sequence variation of the Lewis gene in Pakistani populations and provided the first genetic data on FUT3 in these two ethnic groups from Pakistan. The allele types and their frequencies showed that these ethnic groups exhibit more Caucasian components.