Molecular characterization of erythrocyte receptor genes, CR1, DARC and band 3 required for malaria parasite invasion

Abstract

Malaria is still among the most severe infectious diseases at the dawn of the twenty-first century and remains a major global health problem. Five species of the Plasmodium parasite cause malaria. The parasite life cycle takes place in two hosts, the mosquito and the mammalian host; however, asexual parasite infection within the blood stream is responsible for the symptoms of the disease. This research focused on understanding the erythrocyte polymorphisms of some of the genes involved in invasion. Mutations that lessen the competence of the merozoite in invading erythrocytes would confer a selective advantage to the host and might be expected to increase in frequency over time through natural selection in malaria endemic regions. This study identified the polymorphisms in DARC, CR1 and Band 3 genes in a malaria endemic population. 93 samples from patients with severe malaria from Kilifi District Hospital were PCR amplified (at the 3 genes) and capillary sequenced and SNPs identified. Multiple sequence alignments using MEGA genetics software revealed a number of polymorphisms (SNPs) in the three receptor genes. Most of the polymorphisms occurred in the non-coding regions (promoters and introns) and a few were in the coding regions. The few SNPs in the coding region may be due to the need to prevent change in the protein structure and preserve function since these receptors have other biological functions other than acting as receptors for the malaria parasite. DARC sequence analysis showed that all the individuals sampled were duffy negative. Tajima’s D statistic, Fu and Li’s D and Fu and Li’s F test statistics showed that the SNPs in all the three genes were not under selection and therefore the mutations occurring in these genes were evolving randomly and are potentially driven by genetic drift. Since the samples were biased to severe malaria, the results do not fully depict the Kilifi population genetic diversity.