Mutant/mutation
The mutant lacks expression of TRAP (thrombospondin-related anonymous protein).

Protein (function)
TRAP is a type 1 transmembrane protein, containing two adhesive domains in its extracellular portion, an A-domain of von Willebrand factor and a thrombospondin type I repeat (TSR, TSP). TRAP is located in the micronemes of sporozoites. The protein plays a role in the gliding motility of sporozoites and invasion of host cells.

The role of the different domains of the protein in motility and invasion has been analysed in mutant parasites expressing mutated forms of TRAP (see below).

Phenotype
The phenotype analyses show that the lack of expression of TRAP results in the loss of the gliding motility of the sporozoites. The mutant sporozoites show a strongly reduced capacity to invade salivary glands and infectivity to the mammalian host.

Additional information
This mutant that lacks expression of TRAP has been complemented with a wild-type copy of the trap gene, introduced on episomes that contain the trap gene and the human dihydrofolate reductase (hdhfr) as a drug-selectable marker which confers resistance to the antifolate drug WR99210 (Sultan, A.A. et al., 2001, Mol. Biochem. Parasitol. 113, 151-6). Complementation resulted in restoration of the wild type phenotype.

In the same study mutants are described (INT1, INT2) that have been generated using a construct that integrates by single cross-over integration. The disadvantage of using such integration constructs is that the construct can be removed from the genome, thereby restoring the wild type genotype. One mutant has been deposited at MR4 (MRA-265)

Adhesion of sporozoites of this mutant has been analysed in another study (Hegge et al., 2010, FASEB J; PMID: 20159960). Mutant sporozoites showed significant weaker adhesion on glass slides as compared to wild type parasites.

Other mutants
A. P. yoelii mutant has been generated that lacks expression of TRAP (RMgm-53).
P. berghei mutants have been generated with mutated cytoplasmic tails of TRAP (RMgm-54; RMgm-55; RMgm-56; RMgm-57; RMgm-149; RMgm-150; RMgm-151).
Other P. berghei mutants have been generated with mutated extracellular (adhesive) domains (A-domain: RMgm-48, RMgm-49; TSR domain: RMgm-50; RMgm-51; A-domain and TSR domain: RMgm-52).
A P. berghei mutant has been generated in which the endogenous P. berghei trap was replaced with (mutated forms of) P. falciparum trap (RMgm-58).