Mutant/mutation
The mutant expresses a mutated version of EXP1; the C2 terminal region (93 bp) of the exp1 gene is deleted. In addition it expresses GFP under control of the eef1a constitutive promoter

Protein (function)
Exp1 (HEP17; circumsporozoite-related antigen) is a protein that localizes to the parasitophorous vacuole membrane (PVM) of blood stages and liver stages

Phenotype
Unsuccessful attempts to disrupt the exp1 indicates an essential function for blood stage development (see RMgm-4125).
The mutant expressing the mutated form of EXP1 lacking the C2 terminal region has a normal development of blood stages. Liver stage development of the mutant is impaired resulting in significant reduction of 'late liver stage' parasite loads and delayed blood-stage patency.

Evidence is presented that:
The characteristic movement of infectious sporozoites and their invasion capacity were not impaired in the PbEXP-1ΔC2 parasites. Additionally, immunofluorescence microscopy analysis of Huh7 cells infected with clonal PbEXP-1ΔC2 lines and stained with antibodies against the PVM proteins UIS4 and EXP-1 indicated that neither the integrity of the vacuolar membrane nor the localization of EXP-1 were compromised in transgenic parasites. Evidence is presented for reduced 'late-liver stage' parasite loads in liver of mice infected with the mutant.

Additional information
EXP1 is located in the PVM. Evidence is presented that the C-terminal domain of EXP-1 faces the hepatocyte cytoplasm.
Evidence is presented that the C2-terminal region of EXP1 interacts with the host protein  Apolipoprotein H (ApoH). It is suggested that Plasmodium liver stages use EXP-1 to specifically recruit host–hepatocyte ApoH to the parasite–host interface and to potentially mediate uptake of ApoH and/or ApoH-associated proteins or lipids.

Other mutants
See EXP1 for other mutants