Mutant/mutation
The mutant lacks expression of NEK4 protein.

Protein (function)
NEK4 is a serine/threonine NIMA-related kinase; these kinases are mostly described as being involved in controlling/coordinating signalling processes in mitosis.

The NIMA-related protein kinases (Neks) constitute an extended family of eukaryotic mitotic serine/threonine kinases. The best characterized members of the Nek family include NIMA (never in mitosis/Aspergillus), the founding member from the fungus Aspergillus nidulans, and its closest homologue in mammals, Nek2. Initially identified as a kinase essential for mitotic entry in Aspergillus, NIMA has been also shown to participate in nuclear membrane fission. Eleven members of the NIMA kinase family (Nek1-11) have now been identified in various human tissues, and together fulfil a number of cell cycle-related functions in centrosome separation, mitosis, meiosis and checkpoint control. The P. falciparum kinome includes four NIMA-related serine/threonine kinases. Pfnek-1 (PlasmoDB identifier PFL1370w) clusters within the Aspergillus NIMA/human Nek2 branch in phylogenetic trees, while clear orthology to mammalian or yeast Neks could not be assigned for the three other P. falciparum sequences (Pfnek-2, -3 and -4, PlasmoDB identifiers PFE1290w, PFL0080c and MAL7P1.100,respectively).

Phenotype
Cross-fertilization studies with fertile female gametes from an the parasite line P48/45− (that produce defective males and fertile females; RMgm-15) demonstrated that mutant male gametes are fertile and the defect is exclusively female gamete specific.
In the mutant, fertilsation occurs but parasites arrest during zygote development. Flow cytometric analysis of the DNA content of the arrested mutant  zygotes revealed a clear diploid DNA content without meiotic DNA replication after female and male nucleus fusion. This observation indicates that NEK4 is important either just before or during meiosis.

Additional information
Disruption of the P. falciparum ortholog has been succesful (Solyakov et al., 2011, Nat Commun, 2:565) indicating that this gene is not essential for asexual proliferation.
 

Other mutants
An independent P. berghei nek4- mutant (RMgm-60) has been generated that also lacks NEK4 expression and has essentially the same phenotype.