| Successful modification | The parasite was generated by the genetic modification |
| The mutant contains the following genetic modification(s) |
Gene disruption,
Introduction of a transgene
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| Reference (PubMed-PMID number) |
Reference 1 (PMID number) : 22252874
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| MR4 number |
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| Parent parasite used to introduce the genetic modification |
| Rodent Malaria Parasite | P. yoelii |
| Parent strain/line | P. y. yoelii 17XNL |
| Name parent line/clone |
Not applicable
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| Other information parent line | 17XNL is a non-lethal strain of P. yoelii |
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| The mutant parasite was generated by |
| Name PI/Researcher | J.L. Miller; S.H.I. Kappe; S.A. Mikolajczak |
| Name Group/Department | Seattle Biomedical Research Institute |
| Name Institute | Seattle Biomedical Research Institute |
| City | Seattle |
| Country | USA |
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| Name of the mutant parasite |
| RMgm number | RMgm-665 |
| Principal name | P.yoeliiΔmif |
| Alternative name | |
| Standardized name | |
| Is the mutant parasite cloned after genetic modification | Yes |
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| Phenotype |
| Asexual blood stage | Not different from wild type |
| Gametocyte/Gamete | Not different from wild type |
| Fertilization and ookinete | Not different from wild type |
| Oocyst | Not different from wild type |
| Sporozoite | Not different from wild type |
| Liver stage | Less than 50% of mice infected with 1x10(3) P.yoeliiΔmif sporozoites became patent. For mice that became patent, the onset of blood-stage parasitemia was delayed 2 days compared to that with the control. Patency was more frequent in mice after injecting with 1x10(3) P.yoeliiΔmif sporozoites, and the onset of patency was delayed 1 day in mice that did develop blood-stage infection.
Fewer P.yoeliiΔmif liverstage parasites than control parasites were observed in mouse livers; however, these differences were not statistically significant Thus, the initial steps of hepatocyte invasion and dedifferentiation into a trophozoite appeared not to be affected significantly by the deletion of the mif gene. Microscopic valuation of infected livers revealed that the P.yoeliiΔmif parasites were significantly smaller than control P. yoelii parasites at 44 hpi, with the average diameter of a control parasite being 40.1 ± 10.3 µm and the diameter of a mif-deficient parasite being 24.9 ± 7.6 µm |
| Additional remarks phenotype | Mutant/mutation
The mutant lacks expression of macrophage migration inhibitory factor (MIF).
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 Plasmodium MIF 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 (Augustijn et al., Infect Immun. (2007),75:1116-28).
Phenotype
Phenotype analyses indicate that mutants lacking expression of MIF have a normal blood stage and mosquito development that is not different from wild type parasites. Liver stages of the mutants are affected in development as shown by a delay of the prepatent period in mice infected with mutant sporozoites and a reduced size of developing liver stages.
Additional information
See RMgm-26 for a P. berghei mutant lacking expression of MIF. This mutant showed normal development throughout the complete life cycle. However, no detailed analyses of liver stage development have been published for this mutant
By RT-PCR Py-mif transcripts were detected in mixed blood-stage parasites and 24-h and 44-h liver-stage schizonts but were not observed in infectious salivary gland sporozoites. By IFA using a polyclonal antibody raised against Py-MIF, Py-MIF was detected at low levels in salivary gland sporozoites, but its expression was strong in liver-stage schizonts. The small amounts of MIF observed in sporozoites were not likely to be unspecific staining, since a similar pattern was observed in parasites expressing a myc-tagged version of Py-MIF by use of an anti-myc antibody. At 24 h postinfection (hpi), Py-MIF was distributed uniformly throughout the cytoplasm of liver stages. At 48 hpi, at which point nuclear centers had formed in the late schizonts, Py-MIF appeared to be restricted to the interior of the parasites and was concentrated in globular patterns. In 16-h and 30-h liver-stage schizonts, MIF exhibited a uniform distribution throughout the parasite, while at a later time point (44 hpi) Py-MIF became more compartmentalized and the distribution was focused in the nuclear centers. Throughout the exoerythrocytic stages, Py-MIF staining was always observed within the confines of the parasite and never within the host cell, as shown by staining with antibodies against the parasitophorous vacuole membrane (PVM) marker UIS4. However, the parasite plasma membrane is in close proximity to the PVM. Thus, it was difficult to determine whether some MIF was also found in the vacuolar lumen. No evidence was found for secretion of Py-MIF by liver stages
Other mutants
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 transgenic mutant P. berghei expressing c-myc-tagged MIF.
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-583: A P. yoelii (17XL) mutant containing one additional copy of the macrophage migration inhibitory factor gene (mif) of P. yoelii integrated into the dhfr/ts gene locus
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*RMgm-665
