Morphogenesis inTrypanosoma cruziepimastigotes proceeds via a highly asymmetric cell division

Abstract

AbstractTrypanosoma cruziis a protist parasite that is the causative agent of Chagas’ disease, a neglected tropical disease endemic to the Americas.T. cruzicells are highly polarized and undergo morphological changes as they cycle within their insect and mammalian hosts. Work on related trypanosomatids has described cell division mechanisms in several life-cycle stages and identified a set of essential morphogenic proteins that serve as markers for key events during trypanosomatid division. Here, we use Cas9-based tagging of morphogenic genes, live-cell imaging, and expansion microscopy to study the cell division mechanism of the insect-resident epimastigote form ofT. cruzi,which represents an understudied trypanosomatid morphotype. We find thatT. cruziepimastigote cell division is highly asymmetric, producing one daughter cell that is significantly smaller than the other. Daughter cell division rates differ by 4.9 h, which may be a consequence of this size disparity. Many of the morphogenic proteins identified inT. bruceihave altered localization patterns inT. cruziepimastigoes, which may reflect fundamental differences in the cell division mechanism of this life cycle stage, which widens and shortens the cell body to accommodate the duplicated organelles and cleavage furrow rather than elongating the cell body along the long axis of the cell, as is the case in life-cycle stages that have been studied inT. brucei. This work provides a foundation for further investigations ofT. cruzicell division and shows that subtle differences in trypansomatid cell morphology can alter how these parasites divide.Author SummaryTrypanosoma cruzicauses Chagas’ disease, which is among the most neglected of tropical diseases, affecting millions of people in South and Central America along with immigrant populations around the world.T. cruziis related to other important pathogens such asTrypanosoma bruceiandLeishmania spp,which have been the subject of molecular and cellular characterizations that have provided an understanding of how these organisms shape their cells and undergo division. Work inT. cruzihas lagged due to an absence of molecular tools for manipulating the parasite and the complexity of the original published genome; these issues have recently been resolved. Building on work inT. brucei, we have studied the localization of key cell cycle proteins and quantified changes in cell shape during division in an insect-resident form ofT. cruzi. This work has uncovered unique adaptations to the cell division process inT. cruziand provides insight into the range of mechanisms this family of important pathogens can employ to colonize their hosts.