Vanagas Laura, Dalmasso Maria C, Dubremetz Jean F, Portiansky Enrique L, Olins Donald E, Angel Sergio O
Laboratorio de Parasitología Molecular, IIB-INTECH, CONICET-UNSAM, Av. Intendente Marino Km. 8·2, C.C 164, (B7130IIWA), Chascomús, Prov. Buenos Aires, Argentina.
Parasitology. 2013 Aug;140(9):1104-10. doi: 10.1017/S0031182013000504. Epub 2013 May 23.
Toxoplasma gondii is an apicomplexan intracellular protozoan parasite responsible for toxoplasmosis, a disease with considerable medical and economic impact worldwide. Toxoplasma gondii cells never lose the nuclear envelope and their chromosomes do not condense. Here, we tested the murine monoclonal antibody PL2-6, which labels epichromatin (a conformational chromatin epitope based on histones H2A and H2B complexed with DNA), in T. gondii cultured in human fibroblasts. This epitope is present at the exterior chromatin surface of interphase nuclei and on the periphery of mitotic chromosomes in higher eukaryotes. PL2-6 reacted with T. gondii H2A and H2B histones in Western blot (WB) assays. In addition, the antibody reacted with the nuclear fraction of tachyzoites, as a single band coincident with H2B histone. In the T. gondii tachyzoite stage, PL2-6 also had peripheral nuclear localization, as observed by epifluorescence/confocal microscopy and immunoelectron microscopy. Confocal analysis showed that epichromatin is slightly polarized to one face of the parasite exterior chromatin surface. In replicating tachyzoites, PL2-6 also labels the exterior chromatin surface, covering the face of both segregating nuclei, facing the plasma membrane of the mother cell. The possible role of epichromatin in T. gondii is discussed.
刚地弓形虫是一种顶复门细胞内原生动物寄生虫，可引发弓形虫病，该病在全球范围内具有重大的医学和经济影响。刚地弓形虫细胞从不失去核膜，其染色体也不会浓缩。在此，我们在人成纤维细胞中培养的刚地弓形虫中测试了鼠单克隆抗体PL2-6，该抗体可标记表染色质（一种基于与DNA复合的组蛋白H2A和H2B的构象染色质表位）。在高等真核生物中，该表位存在于间期细胞核的外部染色质表面以及有丝分裂染色体的周边。在蛋白质免疫印迹（WB）分析中，PL2-6与刚地弓形虫的H2A和H2B组蛋白发生反应。此外，该抗体与速殖子的核部分发生反应，呈现出与H2B组蛋白一致的单一条带。在刚地弓形虫速殖子阶段，通过落射荧光/共聚焦显微镜和免疫电子显微镜观察发现，PL2-6也具有周边核定位。共聚焦分析表明，表染色质略微偏向寄生虫外部染色质表面的一侧。在正在复制的速殖子中，PL2-6也标记外部染色质表面，覆盖两个分离细胞核面向母细胞质膜的面。本文讨论了表染色质在刚地弓形虫中的可能作用。
