BACKGROUND: @entity3964 sexual development plays a fundamental role in the transmission and spread of @entity311 . The ability to generate gametocytes can be lost during culture in vitro, often associated with the loss of a subtelomeric region of chromosome 9. Gametocytogenesis starts with erythrocyte invasion by a sexually committed merozoite, but the first available specific marker of sexual differentiation appears only from 24  h post invasion. METHODS: Specific antibodies and gene fusions were produced to study the timing of expression and the sub-cellular localization of the @entity3964 Gametocyte EXported Protein-5 (PfGEXP5), encoded in the subtelomeric region of chromosome 9. Expression patterns were examined in wild-type parasites and in parasite lines mutated in the Apetala2-G (AP2-G) transcription factor, governing a cascade of early sexual stage specific genes. RESULTS: PfGEXP5 is highly expressed in early sexual stages and it is actively exported to the infected erythrocyte cytoplasm from as early as 14  h post-invasion in haemozoin-free, @entity5 . The pattern of PfGEXP5 expression and export is similar in wild-type parasites and in independent AP2-G defective parasite lines unable to produce gametocytes. CONCLUSIONS: PfGEXP5 represents the earliest post-invasion sexual stage marker described to date. This provides a tool that can be used to identify sexually committed ring stage parasites in natural infections. This early gametocyte marker would enable the identification and mapping of @entity311 transmission reservoirs in @entity1 populations and the study of gametocyte sequestration dynamics in infected individuals. The fact that regulation of PfGEXP5 does not depend on the AP2-G master regulator of parasite sexual development suggests that, after sexual commitment, differentiation progresses through multiple checkpoints in the early phase of gametocytogenesis.

Specific expression and export of the XXXX Gametocyte EXported Protein-5 marks the gametocyte ring stage.

@entity5 :: ('MESH:D009369', 'Disease') :: ['ring stage-like parasites'] @entity311 :: ('MESH:D008288', 'Disease') :: ['malaria'] @entity1 :: ('9606', 'Species') :: ['human'] @entity3964 :: ('5833', 'Species') :: ['P. falciparum', 'Plasmodium falciparum']
@entity3964 :: (5833,Species) :: ['Plasmodium falciparum']
