Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, UFRJ, Rio de Janeiro, RJ, Brazil.
Laboratório de Microbiologia, Diretoria de Metrologia Aplicada às Ciências da Vida, Instituto Nacional de Metrologia, Qualidade e Tecnologia- Inmetro, Rio de Janeiro, RJ, Brazil.
Parasit Vectors. 2018 Feb 6;11(1):83. doi: 10.1186/s13071-018-2664-4.
Trypanosoma cruzi uses several strategies to survive in different hosts. A key step in the life-cycle of this parasite is metacyclogenesis, which involves various morphological, biochemical, and genetic changes that induce the differentiation of non-pathogenic epimastigotes into pathogenic metacyclic trypomastigotes. During metacyclogenesis, T. cruzi displays distinct morphologies and ultrastructural features, which have not been fully characterized.
We performed a temporal description of metacyclogenesis using different microscopy techniques that resulted in the identification of three intermediate forms of T. cruzi: intermediates I, II and III. Such classification was based on morphological and ultrastructural aspects as the location of the kinetoplast in relation to the nucleus, kinetoplast shape and kDNA topology. Furthermore, we suggested that metacyclic trypomastigotes derived from intermediate forms that had already detached from the substrate. We also found that changes in the kinetoplast morphology and kDNA arrangement occurred only after the repositioning of this structure toward the posterior region of the cell body. These changes occurred during the later stages of differentiation. In contrast, changes in the nucleus shape began as soon as metacyclogenesis was initiated, while changes in nuclear ultrastructure, such as the loss of the nucleolus, were only observed during later stages of differentiation. Finally, we found that kDNA networks of distinct T. cruzi forms present different patterns of DNA topology.
Our study of T. cruzi metacyclogenesis revealed important aspects of the morphology and ultrastructure of this intriguing cell differentiation process. This research expands our understanding of this parasite's fascinating life-cycle. It also highlights the study of T. cruzi as an important and exciting model system for investigating diverse aspects of cellular, molecular, and evolutionary biology.
克氏锥虫利用多种策略在不同宿主中生存。该寄生虫生命周期中的一个关键步骤是循环转变，涉及各种形态、生化和遗传变化，诱导非致病性的循环体转化为致病性的循环体。在循环转变过程中，克氏锥虫表现出不同的形态和超微结构特征，但尚未得到充分描述。
我们使用不同的显微镜技术对循环转变进行了时间描述，结果鉴定出克氏锥虫的三种中间形式：中间形式 I、II 和 III。这种分类是基于形态和超微结构方面的，如动基体相对于细胞核的位置、动基体的形状和 kDNA 拓扑结构。此外，我们认为循环体衍生自已经脱离基质的中间形式。我们还发现，动基体形态和 kDNA 排列的变化仅在该结构重新定位到细胞体的后区域后才发生。这些变化发生在分化的后期。相比之下，细胞核形状的变化早在循环转变开始时就发生了，而核超微结构的变化，如核仁的丧失，仅在分化的后期观察到。最后，我们发现不同克氏锥虫形式的 kDNA 网络呈现出不同的 DNA 拓扑结构模式。
我们对克氏锥虫循环转变的研究揭示了这个有趣的细胞分化过程的形态和超微结构的重要方面。这项研究扩展了我们对该寄生虫迷人生命周期的理解。它还强调了对克氏锥虫的研究，作为研究细胞、分子和进化生物学的不同方面的重要而令人兴奋的模型系统的重要性。
