| Successful modification | The parasite was generated by the genetic modification |
| The mutant contains the following genetic modification(s) |
Gene disruption
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| Reference (PubMed-PMID number) |
Reference 1 (PMID number) : 19148267
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| MR4 number |
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| Parent parasite used to introduce the genetic modification |
| Rodent Malaria Parasite | P. berghei |
| Parent strain/line | P. berghei ANKA |
| Name parent line/clone |
P. berghei ANKA 2.34
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| Other information parent line | P. berghei ANKA 2.34 is a cloned, gametocyte producer line of the ANKA strain (PubMed: PMID: 15137943). |
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| The mutant parasite was generated by |
| Name PI/Researcher | P. Srinivasan; M. Jacobs-Lorena |
| Name Group/Department | Department of Molecular Microbiology and Immunology |
| Name Institute | Malaria Research Institute, John Hopkins School of Public Health |
| City | Baltimore, Maryland |
| Country | USA |
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| Name of the mutant parasite |
| RMgm number | RMgm-176 |
| Principal name | rom1(-) |
| Alternative name | |
| Standardized name | |
| Is the mutant parasite cloned after genetic modification | Yes |
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| Phenotype |
| Asexual blood stage | Parasitemia develops slower in mice infected with the mutant parasites. Peak parasitemias in mice are comparable to those in wild type infected mice. More then 80% of mice infected with mutant parasites survive infection and clear the parasites from the blood. |
| Gametocyte/Gamete | Not different from wild type |
| Fertilization and ookinete | Normal numbers of ookinetes are produced. A strong reduction in oocyst production. |
| Oocyst | A strong reduction in oocyst production (mean number of oocysts in wild type ranging from 79-213 and in mutants 3-124). Subsequent development of mutant oocysts appears to be normal. The number of mutant sporozoites in oocysts was similar to wild-type oocysts. |
| Sporozoite | A strong reduction in oocyst production (mean number of oocysts in wild type ranging from 79-213 and in mutants 3-124). Subsequent development of mutant oocysts appears to be normal. The number of mutant sporozoites in oocysts was similar to wild-type oocysts. No differences of salivary gland invasion of the mutant sporozoites could be detected. Salivary gland sporozoites showed normal gliding motility. The efficiency of liver infection in vivo of the mutant sporozoites was lower (68%) compared to wild type sporozoites. |
| Liver stage | The efficiency of liver infection in vivo of the mutant sporozoites was lower (68%) compared to wild type sporozoites. |
| Additional remarks phenotype | Mutant/mutation
The mutant lacks expression of rhomboid protease ROM1.
Protein (function)
Rhomboid proteins are intra-membrane proteases that play a role in multiple processes. They belong to a family of serine proteases that cleave cell-surface proteins within their transmembrane domains. The Plasmodium genome encodes a total of 8 rhomboid proteases (ROM1, 3, 4, 6, 7, 10; Dowse, TJ and Soldati, D, 2005, Trends Parasitol 21, 254-58) that show stage-specific expression patterns and includes proteins upregulated in gametocytes and sporozoites. ROM1 is expressed in both the blood stages and mosquito stages (sporozoites). ROM1 was localized to organelles of the apical complex of merozoites and was shown to be able to cleave different adhesins of all invasive stages (merozoites, ookinetes, sporozoites).
Phenotype
The phenotype analyses indicate that ROM1 plays distinct roles during parasite development. It is non-essential but appears to play a role in blood stages, the transformation of ookinetes into oocysts and in the establishment of infection of the liver by the sporozoite. ROM1 is not required for sporozoite invasion of the salivary glands.
Additional information
The ROM1 gene has been disrupted into the genome by single cross-over integration. Therefore the possibility exists of reversion to the wild-type genotype by removal of the integrated DNA construct. The phenotype analyses are performed with only a single mutant parasite line.
Evidence is presented that TRAP (PF13_0201; PB000374.03.0 ; Thrombospondin-related anonymous protein) is not a substrate for ROM1.
Mice that cleared infections with the mutant parasites developed protective immune responses and were protected against challenge with wild type parasites.
Other mutants
RMgm-659: P. yoelii mutant lacking expression of ROM1
RMgm-660: P. yoelii mutant expressing an N-terminally triple HA-tagged ROM1
See RMgm-187 for unsuccessful attempts to disrupt rhomboid protease ROM4 in P. berhei.
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*RMgm-176
