Mutant/mutation
The mutant lacks expression of S6 (sporozoite specific gene 6; TREP, TRAP-related protein; UOS3, upregulated in oocyst sporozoites).

Protein (function)
S6 is a transmembrane protein that possesses a short cytoplasmic tail typical of members of the TRAP/MIC2 family of proteins as well as a single  thrombospondin type I repeat (TSR, TSP) domain. 
S6 has been identified as a sporozoite specific protein 6 (S6) in P. yoelii by analysis of transcripts in sporozoites (Kaiser et al.,  2004, Mol. Microbiol. 51, 1221-32) . The gene encoding S6 is mainly transcribed in midgut (oocyst derived) sporozoites. In salivary gland sporozoites the level of transcription is low. This is in contrast to the two other proteins  belonging to the TRAP/MIC family of proteins, TRAP (PF13_0201) and TLP (PFF0800w), which are mainly expressed in salivary gland sporozoites.

Phenotype
The phenotype analyses indicate a role of S6 in gliding motility of midgut (oocyst derived) sporozoites and invasion of salivary glands. Morover the results of infection of mice and rats by mosquito bite or inoculation of purified sporozoites indicate that TREP is not essential for infectivity to the mammalian host.

Additional information
Other mutants lacking expression of S6 has been generated and analysed (see RMgm-145; RMgm-305). In these studies the protein is named TREP or UOS3. These mutants show a comparable phenotype.

See also GenBank accession number FJ160771 (S6) and FJ167344 (TREP) for the correct sequence of the gene encoding S6/TREP.

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
RMgm-145: A mutant lacking expression of TREP/S6/UOS3 (P. berghei)
RMgm-305: A mutant lacking expression of TREP/S6/UOS3 (P. yoelii)
RMgm-306: A mutant expressing a c-myc tagged version of TREP/S6/UOS3 (P. yoelii)