Nucleolus visualized via nucleophosmin

Movie. Z-stack and timelapse movie of nucleoli. The left panel shows a Z-stack of a live hiPS cell colony expressing mEGFP-tagged nucleophosmin. Cells were imaged in 3D on a spinning-disk confocal microscope. Right panel is the same image as the left but with contrast enhanced to visualize dimmer localization in mitotic cells. Movie starts at the bottom of the cells and ends at the top. Scale bar = 5µm.

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Movie. Z-stack and timelapse movie of nucleoli. Timelapse movie of a live hiPS cell colony expressing mEGFP-tagged nucleophosmin. Cells were imaged on a spinning-disk confocal microscope every 3 min. Image is a maximum intensity projection through the volume of the cells. Frames were histogram matched to adjust for photobleaching. Movie plays at 900x real time. Scale bar = 5 µm.

Observations

• Nucleophosmin marks the granular component of the nucleolus, the nuclear subcompartment where ribosomes are made.
• During much of interphase the nucleolus exists in one to several large, textured clusters within the nucleus of hiPS cells. During cell division, the nucleolus appears to ‘melt’ and then dissociate. After cell division, the nucleolus reassembles, first into small particles and progressing into the larger textured clusters observed during interphase.
• The mEGFP-tagged nucleophosmin exhibits many similarities with the mEGF-tagged fibrillarin, another marker of the nucleolus. However, it also exhibits notable differences, including its specific localization within the nucleolus, as each line marks a different component of the nucleus. The granular component of the nucleolus where nucleophosmin resides forms hollow-looking spheres, giving the nucleolus a mesh-like appearance when imaged with this marker.​