Molecular analysis of Bombay phenotype cases seen in India

Abstract

Background and ObjectivesThe Bombay phenotype cases do not express the ABH antigens on red blood cells and in body secretions because of the inactivation of H (FUT1) gene and Secretor (FUT2) genes. This rare phenotype was first detected in Mumbai, India, previously known as ‘Bombay’. The presence of T725G mutation in FUT1 gene and deletion of FUT2 gene, both in homozygous condition, has been found to be the cause of Bombay phenotype in individuals originating from India. Thus, the objective of this study was micromapping of all the cases of Bombay phenotype identified at our Institute during the last 60 years and molecular analysis of FUT1 and FUT2 genes in a large number of Bombay phenotype cases.Material and MethodsBombay phenotype cases were confirmed by conventional serological techniques. FUT1 gene in 89 cases was screened for T725G alteration by PCR–RFLP. Deletions in FUT2 gene were detected by specific pairs of primers. Similarly, FUT1 and FUT2 genes were sequenced in all control samples.ResultsIn the present series, 74·2% Bombay phenotype cases were originating from Maharashtra state. T725G was found to be the only mutation in homozygous condition in FUT1 gene in all cases of Bombay phenotype. Similarly, they were homozygous for 10‐kb deletion covering entire FUT2 gene.ConclusionAll the cases of Bombay phenotype reported in this study, originating from different states of India, showed only T725G alteration in FUT1 gene and 10‐kb deletion covering entire FUT2 gene suggesting the unicentric origin of this rare phenotype in India.