Fig. 2.

Nuclear RNA foci undergo dynamic changes during cell cycles. In this set of figures, cytoskeleton is stained green with alpha-tubulin to show the structure of mitosis. In early prophase (A), cells start rounding up. Nucleolus fades. Chromatin condenses to form chromosomes. Cells contain more nuclear RNA foci and no foci are seen in cytoplasm. In late prophase (or prometaphase) (B), spindle fibers form. Nuclear envelop starts breaking down. Foci are seen released from nucleus (appearing outside of DAPI area). In metaphase (C, D), chromosomes align with their centromeres on the equator across the center of the cell, spindle fibers attach to centromere. The nuclear envelop disappears. Foci vary in size and number but in general are dissipating. Through anaphase (E) and telophase (F), chromatids of each chromosome separate into daughter chromosomes and move to opposite poles. Remaining foci are randomly distributed between the two daughter cells. In cytokinesis (G, H), cell membrane pinches in around the middle of the cells. A contractile ring cleaves the cells into two daughter cells. Foci drop in number and size and remaining foci are randomly distributed to daughter cells at the end of this stage. After cytokinesis, microtubules reorganize into a new cytoskeleton for the return to interphase. A new nuclear envelop forms around each region of chromosomes. Foci can be trapped in the nucleus or left in the cytoplasm (I). If cells get out of cell cycle, foci will further accumulate and grow larger (J)