Size variation in chromosomes from independent cultured isolates of Plasmodium falciparum

Abstract

The complexity of the life cycle of the protozoan malaria parasite Plasmodium falciparum has hindered genetic analysis; even the number of chromosomes in P. falciparum is uncertain. The blood stages of rodent malaria parasites are haploid and hybridization with cloned complementary DNAs similarly suggests a haploid genome in P. falciparum blood stages (ref. 4 and our unpublished results). A novel approach to karyoptic and linkage analysis in P. falciparum has been provided recently by the technique of pulsed-field gradient (PFG) gel electrophoresis, which allows the fractionation of DNA molecules of 30-3,000 kilobases (kb), a range including the sizes of intact chromosomal DNA molecules from eukaryotes such as yeast and trypanosomatids. We describe here the fractionation by PFG electrophoresis of chromosomal DNA molecules from P. falciparum into at least seven discrete species which vary in size by up to 20% between different isolates. Several genes for P. faciparum antigens which contain repetitive sequences are located on different chromosomes. Surprisingly, two of the chromosomes seem to contain the same sequences.

Subtelomeric chromosome deletions in field isolates of Plasmodium falciparum and their relationship to loss of cytoadherence in vitro.

“…Field isolates were collected from patients in Madang, Papua New Guinea, and cultured until schizont stage (1), and chromosome blocks were prepared as described (12). A twice-cloned Brazilian isolate, ItG2F6 (9), which had been in long-term culture, was recloned by limiting dilution (13) and by using a fluorescence-activated cell sorter.…”

Chromatin structure determines the sites of chromosome breakages in Plasmodium falciparum

“…However, it has been observed that the P.falciparum genome is highly polymorphic and subject to frequent DNA rearrangements (2,3,4,5). In other human parasites, such as Trypanosomes, DNA rearrangements are responsible for creating novel phenotypes and thus, are indicative of a mechanism generating antigenic variation (6).…”

Antibodies to the glutamate dehydrogenase ofPlasmodium falciparum

“…They found that heterologous probes to the enzymes dihydrofolate reductase (mouse) and thymidylate kinase (yeast), hybridize to restriction digest fragments of DNA from various species of malaria parasites. Such an approach might open the way for sequence studies or chromosomal assignment (Kemp, Corcoran, Coppel, Stahl, Bianco, Brown & Anders, 1985) of the genes for the glycolytic enzymes which have long been used as genetic markers in Plasmodium (Walliker, 1983) as well as in other protozoan parasites.…”