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The Plasmodium falciparum, Nima-related kinase Pfnek-4: a marker for asexual parasites committed to sexual differentiation.
Reininger L., Garcia M., Tomlins A., Müller S., Doerig C.
Malaria Journal 11, 1 (2012) 250 - http://www.hal.inserm.fr/inserm-00739795
The Plasmodium falciparum, Nima-related kinase Pfnek-4: a marker for asexual parasites committed to sexual differentiation.
Luc Reininger () 1, 2, 3, Miguel Garcia4, Andrew Tomlins2, Sylke Müller2, Christian Doerig2, 3, 5
1 :  P3H - Phophorylation de protéines et Pathologies Humaines
CNRS : USR3151 – Université Pierre et Marie Curie (UPMC) - Paris VI
Station Biologique de Roscoff Place Georges Teissier 29680 Roscoff
2 :  Wellcome Trust Centre for Molecular Parasitology
Institute of Infection, Immunity & Inflammation – College of Medical, Veterinary and Life Sciences – University of Glasgow
120 University Place - Glasgow, G12 8TA
3 :  Kinomique fonctionelle des parasites responsables du paludisme
INSERM : U609 – École Polytechnique Fédérale de Lausanne
Global Health institute, EPFL-SV-GHI CE 3 316 CH 1015 Lausanne
4 :  FCCF-SV-EPFL - Flow Cytometry Core Facility
École Polytechnique Fédérale de Lausanne (EPFL)
Station 15, Lausanne CH-1015
5 :  Microbiology
Monash University
Wellington Road, Clayton, VIC 3800
ABSTRACT: BACKGROUND: Malaria parasites undergo, in the vertebrate host, a developmental switch from asexual replication to sexual differentiation leading to the formation of gametocytes, the only form able to survive in the mosquito vector. Regulation of the onset of the sexual phase remains largely unknown and represents an important gap in the understanding of the parasite's complex biology. METHODS: The expression and function of the Nima-related kinase Pfnek-4 during the early sexual development of the human malaria parasite Plasmodium falciparum were investigated, using three types of transgenic Plasmodium falciparum 3D7 lines: (i) episomally expressing a Pfnek-4-GFP fusion protein under the control of its cognate pfnek-4 promoter; (ii) episomally expressing negative or positive selectable markers, yeast cytosine deaminase-uridyl phosphoribosyl transferase, or human dihydrofolate reductase, under the control of the pfnek-4 promoter; and (iii) lacking a functional pfnek-4 gene. Parasite transfectants were analysed by fluorescence microscopy and flow cytometry. In vitro growth rate and gametocyte formation were determined by Giemsa-stained blood smears. RESULTS: The Pfnek-4-GFP protein was found to be expressed in stage II to V gametocytes and, unexpectedly, in a subset of asexual-stage parasites undergoing schizogony. Culture conditions stimulating gametocyte formation resulted in significant increase of this schizont subpopulation. Moreover, sorted asexual parasites expressing the Pfnek-4-GFP protein displayed elevated gametocyte formation when returned to in vitro culture in presence of fresh red blood cells, when compared to GFP- parasites from the same initial population. Negative selection of asexual parasites expressing pfnek-4 showed a marginal reduction in growth rate, whereas positive selection caused a marked reduction in parasitaemia, but was not sufficient to completely abolish proliferation. Pfnek-4- clones are not affected in their asexual growth and produced normal numbers of stage V gametocytes. CONCLUSIONS: The results indicate that Pfnek-4 is not strictly gametocyte-specific, and is expressed in a small subset of asexual parasites displaying high rate conversion to sexual development. Pfnek-4 is not required for erythrocytic schizogony and gametocytogenesis. This is the first study to report the use of a molecular marker for the sorting of sexually-committed schizont stage P. falciparum parasites, which opens the way to molecular characterization of this pre-differentiated subpopulation.
Sciences du Vivant/Médecine humaine et pathologie/Maladies infectieuses

Articles dans des revues avec comité de lecture
Malaria Journal (Malar J)
Publisher BioMed Central
ISSN 1475-2875 

Gametocytes – NIMA – Plasmodium falciparum – Ser/Thr protein kinase
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