Mutant/mutation
The mutant contains one additional copy of the macrophage migration inhibitory factor gene (mif) of P. yoelii integrated into the dhfr/ts gene locus (the construct was integrated via a single crossover event instead of the expected double crossover).

Protein (function)
Macrophage migration inhibitory factor (MIF) is a mammalian cytokine that participates in innate and adaptive immune responses. Homologues of mammalian MIF have been discovered in parasite species (nematodes and malaria parasites). Like human MIF, histidine-tagged purified recombinant PMIF shows tautomerase and oxidoreductase activities (although the activities are reduced compared to those of histidine-tagged human MIF) and efficiently inhibits AP-1 activity in human embryonic kidney cells (Augustijn et al., Infect Immun. (2007),75:1116-28). P. berghei MIF is expressed in both the mammalian host and mosquito vector. In blood stages, MIF is secreted into the infected erythrocytes and released upon schizont rupture.
See also RMgm-26 for a P. berghei mutant lacking expression of MIF. This mutant was able to complete the entire life cycle and exhibited no significant changes in growth characteristics or virulence features during blood stage infection. However, rodent hosts infected with this mutant had significantly higher numbers of circulating reticulocytes.

Phenotype
BALB/cByJ mice infected with Py17XL-MIF(+) parasites showed a significant delay in time to death and as well as higher survival rates than those infected with control parasites (see 'additional Information'). These data indicate that that increased expression of Plasmodium MIF by blood-stage  parasites can alter the course of infection and reduce overall mortality.  

See also the phenotype of mutant RMgm-582. This mutant contains 2 additional copies of the macrophage migration inhibitory factor gene (mif) of P. yoelii integrated into the c-ssu-rrna gene locus.

Additional information
Increased expression of pymif Py17XL-MIF(+) parasites was assessed at both RNA and protein levels. Quantitative RT-PCR analysis indicated an increase in expression of approximately 3.6 fold which was comparable to the increase of 3.7 observed at the protein level as measured by immunoblot analysis.

The median survival for Py17XLMIF(+) infected mice in the two experiments was 19 and 20 days respectively, in comparison to 9 and 8.5 days for wt infected mice. In the first experiment, parasitemia in Py17XL-408 MIF(+) infected mice was slightly lower than in wt infected mice during the first week of infection. However, this was not the case in the second experiments where parasitemia levels in the two groups were comparable through day 8 of infection. The surviving mice, in both experiments cleared their infection completely by day 24 post-infection.

Other mutants
RMgm-582: A P.yoelii (Py17X) mutant containing  2 additional copies of the macrophage migration inhibitory factor gene (mif) of P. yoelii integrated into the c-ssu-rrna gene locus. These mif copies are under control of the strong consecutive eef1a promoter.
RMgm-665: A P. yoelii (17XNL) mutant lacking expression of MIF
RMgm-26 is a P. berghei mutant lacking expression of MIF.
RMgm-27 is a transgenic P. berghei mutant expressing GFP-tagged MIF.
RMgm-31 is a P. berghei transgenic mutant expressing c-myc-tagged MIF.