Mutant/mutation
The mutant lacks expression of GEST (gamete egress and sporozoite traversal protein) and expresses GFP under the control of the constitutive eef1α promoter.

Phenotype
Phenotype analyses indicate a role of GEST in the formation of fertile male and female gametes. Evidence is presented that male and female gametes fail to egress from the erythrocyte. Fertilisation, ookinete and oocyst production is strongly reduced.

The low numbers of oocysts produce normal numbers of sporozoites that are able to invade salivary glands. Infectivity of sporozoites to mice is normal after intravenous injection of sporozoites; however, sporozoite infectivity after subcutaneous injection is reduced. Sporozoites showed normal gliding motility and hepatocyte invasion capacity. Evidence is presented for a reduced cell traversal/wounding of mutant sporozoites.

Additional information
An independent mutant lacking expression of GEST has been made in the P. berghei ANKA 2.34 reference line.

Evidence has been presented for a location of GEST in osmiophilic bodies (OB) of male and female gametocytes through analysis of a transgenic mutant expressing GFP-tagged GEST (see mutant RMgm-668). In addition evidence was found for secretion of GEST from OBs upon activation of gametocytes.

Evidence has been presented for secretion of GEST by sporozoites through analysis of a transgenic mutant expressing GFP-tagged GEST (see mutant RMgm-668).

Partial rescue of the phenotype was obtained in complementation studies in which mutant parasites were complemented with either the complete P. berghei gest gene or the P. falciparum gest gene. Those genes were introduced in the mutant by transfection of episomal constructs that contained the hdhfr selectable marker. Complemented mutants were selected with the drug WR99210.

Other mutants
RMgm-668: A mutant expressing a C-terminal GFP-tagged form of GEST