Mutant/mutation
The mutant lacks expression of  MISFIT (male-inherited sporulation factor important for transmission).

Protein (function)
MISFIT is an 180 kDa protein bearing a Formin Homology 2 (FH2) domain, the defining feature of formins, and a nuclear localization signal (NLS).

Phenotype
Phenotype analyses indicate that MISFIT plays a critical role during development of the ookinete into the oocyst. Ookinetes invade the mosquito midgut but are arrested in development during their subsequent transformation into oocysts.Genetic crosses of Δpbmisfit gametes show a strict requirement for a functional male copy of misfit  (see 'Additional information'). Mutant ookinetes show a reduced DNA content, microneme defects and altered transcription profiles of putative cell cycle regulators (see 'Additional information').

Additional information
The phenotype of reduced oocyst formation was independently corroborated by disruption of misfit in the P. berghei 2.34 ANKA genetic background (data not shown).

Mutant ookinetes injected directly into the mosquito hemocoel failed to rescue the phenotype of severely affected formation of oocysts.

MISFIT is localized in the nuclei of male gametocytes (activated and not), zygotes and ookinetes as shown by immunofluorescence analyses of a mutant (RMgm-322) that expresses a c-myc-tagged version of MISFIT (using c-myc antibodies).

Genetic crosses were used  to determine whether the defect leading to the block in ookinete development was carried by the male or the female gametocytes/gametes. Male and female gametes of Δpbmisfit  were crossed with gametes of mutant parasite lines that are defective either in male or in female gamete production. Crosses between Δpbmisfit females and wild type males yielded oocysts of normal number, size, morphology, and capability to sporulate. In contrast, crosses between Δpbmisfit males and wild type females invariably produced oocysts exhibiting the Δpbmisfit phenotype.The results revealed a strict requirement for a functional male copy of misfit.

Ookinetes showed a reduced DNA content (3N instead of 4N) as determined by analysis of microscope images of DAPI-stained ookinetes and flow cytometry of DRAQ5-stained ookinetes. Microarray analyses of mutant and wild type ookinetes provided evidence for altered transcription profiles of putative cell cycle regulators. Electron microscopic analyses showed a severe defect in the micronemes of Δpbmisfit ookinetes (reduced numbers or no micronemes).

Based on the phenotype analyses it has been suggested that MISFIT is involved in the regulation of microtubule remodeling during DNA replication and chromosome segregation in mitosis in male gametocytes and/or meiosis in zygotes.

Other mutants
RMgm-322: A mutant expressing a c-myc tagged version of MISFIT