Contrasting signatures of selection on the Plasmodium falciparum erythrocyte binding antigen gene family.
Erythrocyte binding antigens of Plasmodium falciparum are involved in erythrocyte invasion, and may be targets of acquired immunity. Of the five eba genes, protein products have been detected for eba-175, eba-181 and eba-140, but not for psieba-165 or ebl-1, providing opportunity for comparative analysis of genetic variation to identify selection. Region II of each of these genes was sequenced from a cross-sectional sample of parasites in an endemic Kenyan population, and the frequency distributions of polymorphisms analysed. A positive value of Tajima's D was observed for eba-175 (D=1.13) indicating an excess of intermediate frequency polymorphisms, while all other genes had negative values, the most negative being ebl-1 (D=-2.35) followed by psieba-165 (D=-1.79). The eba-175 and ebl-1 genes were then studied in a sample of parasites from Thailand, for which a positive Tajima's D value was again observed for eba-175 (D=1.79), and a negative value for ebl-1 (D=-1.85). This indicates that eba-175 is under balancing selection in each population, in strong contrast to the other members of the gene family, particularly ebl-1 and psieba-165 that may have been under recent directional selection. Population expansion simulations were performed under a neutral model, further supporting the departures from neutrality of these genes.
Verra
Federica
F
Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom. federica.verra@lshtm.ac.uk
Chokejindachai
Watcharee
W
Weedall
Gareth D
GD
Polley
Spencer D
SD
Mwangi
Tabitha W
TW
Marsh
Kevin
K
Conway
David J
DJ
D000818:Animals; D000953:Antigens, Protozoan / Q000235:genetics*; D001483:Base Sequence; D016054:DNA, Protozoan / Q000235:genetics; D017125:Genes, Protozoan; D014644:Genetic Variation; D006801:Humans; D007630:Kenya; D015810:Linkage Disequilibrium; D016778:Malaria, Falciparum / Q000469:parasitology; D008969:Molecular Sequence Data; D005810:Multigene Family; D010963:Plasmodium falciparum / Q000235:genetics* / Q000276:immunology* / Q000302:isolation & purification; D011110:Polymorphism, Genetic; D015800:Protozoan Proteins / Q000235:genetics*; D011956:Receptors, Cell Surface / Q000235:genetics*; D011995:Recombination, Genetic; D012641:Selection, Genetic; D012689:Sequence Homology, Nucleic Acid
D000953:Antigens, Protozoan; D016054:DNA, Protozoan; C066001:Duffy antigen binding protein, Plasmodium; D015800:Protozoan Proteins; D011956:Receptors, Cell Surface