Molecular basis of RhD-negative phenotype in North Indian blood donor population

Abstract

Background & objectives: RHD gene typing is highly complex due to homology with RHCE genes. Molecular polymorphism of the RHCE and RHD genes have been characterized among various populations, but no studies have been undertaken among Indians. This study was undertaken to assess the genetic basis of RHD-negative phenotype in Indian blood donor population. Methods: Sample from a total of 200 phenotypically RhD-negative blood donors were analyzed for presence of RHD gene using polymerase chain reaction (PCR). RHD genotyping was done using three primer sets designed for exons 4 and 10 and one set for identification of pseudo ( RHDΨ) gene between introns (int) 3 and 4. Amplified PCR products were analyzed by gel-electrophoresis (XY Loper, Uvitech, Cambridge) and confirmed by nucleotide sequencing (ABI 3730 xl 96 capillary system). Results: No PCR product was found in 195/200 (97.5%) of study samples indicating homozygous gene deletion. Of the 5/200 (2.5%) showing RHD gene polymorphisms, 4/200 (2%) were positive for presence of exon 10 only (RHD-CE-D hybrid). RHDΨ gene was not detected in any of the samples tested. One sample showed presence of all three tested regions and was negative for RHDΨ gene. Interpretation & conclusions: RHD gene deletion was found to be the most common cause of an RHD-negative phenotype while RHDΨ gene was, reported to be present in up to 39 per cent of various ethnic populations, but was not detected. RHD-CE-D hybrid gene (found in 2.5% individuals) is important for predicting the requirement of Rh prophylaxis during the antenatal period.

Molecular Background of RhD-positive and RhD-negative Phenotypes in a Saudi Population

“…This result is similar to those found in RhD-negative individuals from Caucasian, Indian, and Iranian populations. [ 16 20 ] Nevertheless, as only RHD exons 3, 4, and 7 were tested in the RhD-negative samples, the possibility remains that some of the samples may have a nonactive hybrid RHD gene rather than a homozygous RHD deletion allele, as both would give negative results by the technique used here. Moreover, in this study, the RHD gene was investigated by means of PCR techniques, which could fail in detecting some RHD negative alleles that could be detected by using gene sequencing methods.…”