Understanding malaria transmission: Targeted disruption of a sexual stage gene, Pfs16

Drugs and vaccines that target only the asexual stages of the parasite may not effective in reducing transmission of Plasmodium. Understanding mechanisms involved in the development of sexual stages of Plasmodium may identify novel targets for drugs and vaccines effective in reducing malaria transmission. Gameto-cytogenesis is a tightly regulated process marked by differentiation of the parasites through distinct morphological changes and expression patterns of sexual stage proteins.; Pfs16 is the earliest known sexual stage specific protein expressed at the onset of gametocytogenesis. Expression of this membrane protein is detected in the first 24 hours of gametocyte development, while the transcripts can be detected in the first few hours. Targeted gene disruption strategy was undertaken to knock out expression of Pfs16 in order to examine its potential functions during sexual development. Three clones were isolated and demonstrated to have a disruption in the coding sequence of Ps16 gene by the insertion of the targeting plasmid. Interestingly, all three “16ko” clones appear to express a putative truncated Pfs16 protein that also showed mis-localization in the parasites. Disruption of Pfs16 gene resulted in a significant reduction in gametocyte production. These “16ko” gametocytes appear to be normal at the phenotypic level. The dramatic reduction in gametocyte production and the lack of male gametocyte exflagellation suggest that Pfs16 may not essential for normal sexual development, and instead may play a role at the onset of gametocyte development and may be required for optimal production of sexual parasites.