Mutant/mutation
The mutant lacks expression of MDV-1/PEG3 and in addition expresses GFP in male gametocytes/gametes and RFP in female gametocytes/gametes/zygotes. The mdv-1/peg3 gene has been disrupted  in mutant RMgm-164. This mutant expresses GFP under control of the male gametocyte specific promoter of PB000791.03.0 (dynein heavy chain, putative) and RFP under the control of the 'female gametocyte specific' promoter  PB000504.02.0 (LCCL domain-containing protein CCP2). The rfp and gfp genes are stably integrated into the genome in the 230p locus. Mutant RMgm-164 does not contain a drug selectable marker which has been removed by the negative selection procedure using the negative selectable marker yfcu (yeast cytosine deaminase and uridyl-phosphoribosyltransferase) and the drug 5-fluorocytosine (5-FC).

Protein (function)
The protein is a gametocyte specific protein and has been named in P. falciparum MDV-1 (male development gene 1) or PEG3. In P. falciparum gametocytes the protein is associated with the osmiophilic bodies, the parasite membrane and all membranous compartments derived from the parasitophorous vacuole membrane. P. falciparum parasites lacking expression of MDV-1/PEG3 were affected in their capacity to produce functional gametocytes, which were unable to be transmitted through mosquitoes.

Phenotype
The phenotype analyses indicate that the lack of expression of MDV-1/PEG3 strongly impairs fertilisation and ookinete formation. The phenotype analyses indicate that the decreased fertilisation rate results from a strongly reduced capacity of both male and female gametocytes/gametes to egress from their host erythrocytes (see also 'Additional information'). The results indicate that MDV-1/PEG3 plays a role in disruption of the parasitophorous vacuole membrane (PVM) and the erythrocyte membrane.

Additional information
MDV-1/PEG3 is expressed in both male and female gametocytes with higher expression in females compared to males. Immunoelectron microcope analysis showed an association of MDV-1/PEG3 with the osmiophilic bodies in female gametocytes. Evidence is presented that during female gamete formation MDV-1/PEG3 is released extracellularly. 
Normal numbers of male and female gametocytes are produced that are able to form gametes.
The mdv-1/peg3 gene has been disrupted in a mutant expressing RFP in female gametocytes/gametes/zygotes in order to determine fertilisation of female gametes and meiosis in zygotes by FACS analysis. Female gametes/zygotes express RFP allowing for FACS selection of the RFP-positive females to be analysed. Before FACS analysis live cells are stained with the DNA specific dye Hoechst 32258 to measure DNA content and determine the ploïdy of female cells by FACS analysis.
Cross-fertilisation studies with wild type male and female gametes showed that both mutant female and mutant male gametocytes/gametes are affected in fertilisation and ookinete formation.
Live light microscope observations on gamete formation and electron microscope analysis provided evidence that both male and female gametes are strongly impaired in emergence/egress from their host erythrocytes and failed to disrupt the parasitophorous vacuole membrane (PVM) and the erythrocyte membrane.

An independent mutant lacking expression of MDV-1/PEG3 has been described (RMgm-231). This mutant showed a slightly different phenotype. Both female and male gametocytes were strongly impaired in fertilisation and production of ookinetes. In addition, ookinetes lacking expression of MDV-1/PEG3 showed an impaired development, suggesting an additional role of MDV-1/PEG3 in the ookinete stage.

Other mutants
RMgm-283: A mutant lacking expression of MDV-1/PEG3, generated in the same study.
RMgm-231: An independent mutant lacking expression of MDV-1/PEG3
RMgm-251: A mutant expressing GFP under the control of the MDV-1/PEG3 promoter.