Mutant/mutation
The mutant lacks expression of PbG377.

Protein (function)
The orthologous gene In P. falciparum, Pfg377, is associated with osmiophilic bodies (OB) and plays a role in the emergence of female gametocytes from the host erythrocyte after induction of gamete formation (de Koning-Ward, T.F. et al. Mol. Microbiol. (2008) 67:278-90).

Phenotype
Production of gametocytes was slightly reduced in clone ΔPbg377-b (622cl1) compared to WT, while the other clone (600cl1) examined was similar to WT.

In female gametocytes typical osmiophilic bodies (OB) were not detected by Transmission Electron Microscopy (TEM) but only tiny osmiophilic vesicles, which were reduced in size compared to OB of WT females. The altered morphology of OB in mutant parasites was confirmed by determining minimum and maximum size values of more than a hundred OB sections present in TEM micrographs of WT and ΔPbg377 gametocytes. These observations indicate that Pbg377 may have a structural role in defining the shape of female OB. Absence of this protein does not result in a near complete lack of OB, as described for P. falciparum mutant lacking Pfg377, but instead results in a dramatic change in OB morphology.

15 min post activation of gametocytes a reduction of approximately 60% in egress of females from the host erythrocyte was observed in mutant parasites compared to the WT, while males emerged normally, as expected. At 20 min, egress of mutant female gametocytes/gametes was comparable to the WT. These observations indicate that in the absence of normal OB, female gametocytes are able to egress from the host erythrocyte, although less efficiently than the WT.

Additional information
Expression in female gametocytes has been demonstrated using anti-PbG377 antibodies. No expression was detected in males.

Evidence is presented for co-localisation with MDV1/PEG3, a protein localised in osmiophilic bodies (OB). Immune electron microscopy (IEM), revealed that both Pbg377 and MDV1/PEG3 reside in the characteristic oval-shaped OB of female gametocytes.

A P. falciparum has been generated lacking expression of Pfg377.  Female gametocytes of this mutant are significantly less efficient in their emergence from the erythrocytes upon induction of gamete formation (de Koning-Ward, T.F. et al. Mol. Microbio. (2008) 67:278-90).

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