Mutant/mutation
The mutant expresses a mutated form of CSP where Pexel I and II domains of CSP were mutated into ANANA and ALAGA (The first, third, and fifth amino acids of pexel I (RNLNE) and pexel II (RLLGD) in wild-type CSP presented mutations from R, L, E and R, L, D to A) 
In addition, the mutant expresses RFP (RedStar) under control of the constitutive eef1a promoter.

Protein (function)
The CS protein is the major protein on the surface of sporozoites and is critical for development of sporozoites within the oocysts and is involved in motility and invasion of both the salivary gland of the mosquito and the liver cells. The protein is also found on the oocyst plasma membrane and on the inner surface of the oocyst capsule. Specific motifs in CS are involved in sporozoite binding to mosquito salivary glands and in sporozoite attachment to heparan sulfate proteoglycans in the liver of the mammalian host. During substrate-dependent locomotion of sporozoites, CS is secreted at the sporozoite anterior pole, translocated along the sporozoite axis and released on the substrate at the sporozoite posterior pole. Following sporozoite invasion of hepatocytes, the CS is released in the host cell cytoplasm.

Phenotype
The number and size of CSPmut oocysts were comparable to those of CSP wild-type parasites. Although a few sporozoites were observed in the hemolymph, none were found in the salivary glands of mosquitoes. Melanization of oocyst from day 7 with different amounts of black dots deposited inside the oocyst capsule on day 12. Under electronic microscopy, some mature CSPmut oocysts generated thousands of sporozoites with normal morphology, but many sporozoites were found to be vacuolated and partially melanized at day 11. The percentage of the melanized CSPmut oocysts increased from an average of 28.2% on day 9, to 49.3% on day 12, and 73.2% on day 15.

Additional information
TEP1 was only observed to bind to the surface of CSPmut oocysts and co-localized with CSP protein inside the mutant oocysts, but not for CSPwt oocysts at day 7 PI. When TEP1 was silenced, however, no oocysts were found to be melanized in CSPmut parasite-infected mosquitoes on day 12 PI, and an increased number of CSPmut sporozoites appeared in the hemolymph. Both the motility and infectivity of CSPmut hemolymph sporozoites were comparable to those of the CSPwt hemolymph sporozoites in vitro, indicating no biological defect in mutant parasites.

Other mutants