MAPPING THE GENETIC-LOCUS IMPLICATED IN CYTOADHERENCE OF PLASMODIUM-FALCIPARUM TO MELANOMA-CELLS

Many lines of Plasmodium falciparum undergo a deletion of the right en d of chromosome 9 during in vitro cultivation accompanied by loss of c ytoadherence to melanoma cells. The deletion also results in loss of e xpression of PfEMP1, the putative cytoadherence ligand, suggesting tha t PfEMP1 or a regulatory gene controlling PfEMP1 expression is encoded in this region. Initially a library of short fragments highly enriche d for the right arm of chromosome 9 was constructed in bacteriophage l ambda. Clones from this library were obtained randomly by the polymera se chain reaction (PCR) technique sequenced and used to screen a yeast artificial chromosome (YAC)-P. falciparum library by PCR so that the region could be cloned and physically mapped in detail. We have used p robes from this region to demonstrate that clones derived from ITG2 ha ve undergone a deletion of intermediate length on chromosome 9. This c ould explain the unusual stability of cytoadherence in these clones.