Molecular analysis of Bombay phenotype cases seen in India

Abstract

Background and Objectives The 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 Methods Bombay 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. Results In 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. Conclusion All 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.

Neonatal testing leading to the identification of Bh (para-Bombay) phenotype in the mother: case report with review of the literature

“…The possible mechanisms of the para-Bombay phenotype are a mutated or a silenced FUT1 gene (H gene) with an active FUT2 gene (secretor SE gene), resulting in expressing ABH substances in secretions. 2 These individuals are homozygous for a nonfunctional FUT1 gene. The common mutations in FUT1 and FUT2 genes in a para-Bombay phenotype identified in recent years are summarized in Table 4.…”

“…The incidence of the Bombay phenotype in the Indian population is approximately 1 in 10,000 and is most often due to a T725G mutation in the FUT1 gene and a 10-kb deletion in the FUT2 gene. 2 The para-Bombay phenotype is either due to a point mutation or a silence mutation on the FUT1 gene with a normal FUT2 gene. 2 As a result, para-Bombay individuals have ABH substances in their secretions and plasma (Type 1 precursor chain) depending on whether or not they inherit ABO genes.…”

“…2 The para-Bombay phenotype is either due to a point mutation or a silence mutation on the FUT1 gene with a normal FUT2 gene. 2 As a result, para-Bombay individuals have ABH substances in their secretions and plasma (Type 1 precursor chain) depending on whether or not they inherit ABO genes. ABH substance in the plasma can be adsorbed onto the red blood cells (RBCs), leading to a weak expression of ABH antigens.…”

Para-Bombay B phenotype: a rare ABH blood group variant at tertiary care hospital, Gwalior India

“…12 All the Bombay phenotype cases reported in India showed only the T725G mutation of FUT1 and the 10 kb gene deletion of FUT2, which are responsible for this rare phenotype, suggesting its unicentric origin. 15 Unlike Bombay, the Para-Bombay blood group individuals can express type 1 chain A, B, and H antigens in their plasma and secretions. The weak A and/or B antigen expression on red cells is due to passively adsorption 2 and could only be detected by the adsorption and elution technique.…”

Para-Bombay phenotype: A case report from a tertiary care hospital from South Gujarat

“…[7] All the Bombay phenotype cases reported in India showed only the T725G mutation of FUT1 and the 10 kb gene deletion of FUT2 which are responsible for this rare phenotype, suggesting its unicentric origin. [11]…”