Nucleolus via Fibrillarin

Z-stack

​High magnification timelapse (cell division)

Figure 1. Movies of fibrillarin in Nucleoli. Left: Z-stack of live hiPS cells expressing mEGFP tagged fibrillarin imaged on a spinning-disk confocal microscope. Images start from the bottom of the cells and end at the top. Right: Timelapse movie of live hiPS cells expressing mEGFP tagged fibrillarin. Images were collected in 3D every 3 minutes for 1.5 hours on a spinning-disk confocal microscope. Image is a maximum intensity projection. Playback speed is 900x real time.

Figure 2. Time series of cell division. A single cell going through cell division taken from the movie on the right.

Observations

• Fibrillarin marks the dense fibrillar component (DFC) of the nucleolus, the nuclear subcompartment where ribosome biogenesis occurs.
• During much of interphase the nucleolus exists in 1-2 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. Low levels of fibrillarin are visible on chromosomes during chromosome segregation in mitosis.