The dynamics of filamentous structures in the apical band, oral crescent, fission line and the postoral meridional filament in Tetrahymena thermophila revealed by monoclonal antibody 12G9

The ciliate Tetrahymena thermophila possesses a multitude of cytoskeletal s tructures whose differentiation is related to the basal bodies - the main m ediators of the cortical pattern. This investigation deals with immunolocal ization using light and electron microscopy of filaments labeled by the mon oclonal antibody 12G9, which in other ciliates identifies filaments involve d in transmission of cellular polarities and marks cell meridians with the highest morphogenetic potential. In Tetrahymena interphase cells, mAb 12G9 localizes to the sites of basal bodies and to the striated ciliary rootlets , to the apical band of filaments and to the fine fibrillar oral crescent. We followed the sequence of development of these structures during division al morphogenesis. The labeling of the maternal oral crescent disappears in pre-metaphase cells and reappears during anaphase, concomitantly with diffe rentiation of the new structure in the posterior daughter cell. In the post erior daughter cell, the new apical band originates as small clusters of fi laments located at the base of the anterior basal bodies of the apical basa l body couplets during early anaphase. The differentiation of the band is c ompleted in the final stages of cytokinesis and in the young post-dividing cell. The maternal band is reorganized earlier, simultaneously with the ora l structure. The mAb 12G9 identifies two transient structures present only in dividing c ells. One is a medial structure demarcating the two daughter cells during m etaphase and anaphase, and defining the new anterior border of the posterio r daughter cell. The other is a post-oral meridional filament marking the s tomatogenic meridian in postmetaphase cells. Comparative analysis of immuno localization of transient filaments labeled with mAb12G9 in Tetrahymena and other ciliates indicates that this antibody identifies a protein bound to filamentous structures, which might play a role in relying polarities of co rtical domains and could be a part of a mechanism which governs the positio ning of cortical organelles in ciliates.