THE CHROMOSOMAL ORGANIZATION OF THE PLASMODIUM-FALCIPARUM VAR GENE FAMILY IS CONSERVED

The var gene family of Plasmodium falciparum encodes the protein PfEMP 1 which is located on the surface of infected erythrocytes and is the receptor that mediates binding to ligands on endothelial cells. This f amily of proteins is responsible for antigenic variation and differenc es In binding phenotype to ligands such as CD36 and ICAM1. We have com pared the organization of the var gene family in three in vitro cloned lines of P. falciparum and show that most var genes are located in th e subtelomeric region of each chromosome closely linked to the repetit ive sequence rep20. While most chromosomes possess var genes in the su btelomeric region, in each in vitro cloned line there are some chromos omes that have deleted subtelomeric repetitive regions which include v ar genes. Comparison of the location of var genes in a field isolate s howed that it does not have any detectable subtelomeric deletions as a ll chromosomes contain var genes and rep20 sequences. We have detected three chromosomes (4, 7 and 12) that contain var gene loci in more st able central regions and the position of these genes on chromosome 4 i n the cloned lines analysed is conserved. The location of most of the var gene family in the subtelomeric region of the genome of P. falcipa rum has important implications for the generation of antigenic diversi ty of the PfEMP1 protein. (C) 1997 Elsevier Science B.V.