Functional Analysis of Inner-Arm Dynein Knockdowns in Trypanosoma brucei



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African Trypanosomasis is an endemic disease in sub-Saharan Africa caused by infection with the Trypanosoma brucei parasite. These unicellular eukaryotic organisms rely heavily on their single flagellum for movement and proliferation. Inside the flagellum, nine outer doublet microtubules surround a central microtubule pair in a structure called the axoneme; movement of the flagellum is dictated by the function of protein complexes called dyneins, which lie between the microtubules of the axoneme. These dyneins act as molecular motors by pushing the microtubules past each other, creating the flagellar beat and waveform. There are several different types of proteins within the dynein complex and two different dynein types within the axoneme. This study looked at two genes believed to encode proteins in the inner-arm dynein: TbDNAH10, the putative inner-arm heavy chain alpha protein, and TbIC95, a probable intermediate chain. In order to analyze the function of these gene products, the genes were individually knocked down using RNA interference, and cells were analyzed for motility, division, and morphological defects. TbDNAH10 knockdowns displayed a severe motility defect and had visible cell division defects. The TbIC95 knockdowns displayed a less severe but still noticeable motility defect, and managed to sustain better proliferation than the TbDNAH10 knockdowns. The results obtained suggest that these genes encode proteins essential for the inner-arm dyneins, and that these dyneins are essential for proper movement of the flagellum.