Chromatin visualized via SMC protein 1A

Movie. High magnification z-stack of a live hiPS cell colony expressing mEGFP-tagged SMC protein 1A. Cells were imaged in 3D on a spinning-disk confocal microscope. Movie starts at the bottom of the cells and ends at the top. Scale bar, 5µm.

Movie. Time-lapse in high magnification movie of a live hiPS cell colony expressing mEGFP-tagged SMC protein 1A. Cells were imaged in 3D on a spinning-disk confocal microscope every 3 min. A single mid-level plane is shown. Frames were histogram matched to adjust for photobleaching. Movie plays at 900x real time. Scale bar, 5 µm.

Movie. Time-lapse in low magnification movie of a live hiPS cell colony expressing mEGFP-tagged SMC protein 1A. Cells were imaged in 3D on a spinning-disk confocal microscope every 5 min. A single mid-level plane is shown. Movie plays at 3000x real time. Scale bar, 20 µm.

Observations

• SMC protein 1A is encoded by the X-linked gene SMC1A and escapes X-chromosome inactivation.
• SMC protein 1A is part of the cohesin complex. Cohesin is important for controlling chromosomal shape and organization in interphase and mitosis. Cohesin is best known for its role in joining sister chromatids during part of the cell cycle between DNA replication and anaphase so that that chromatids are properly distributed between daughter cells.
• In hiPS cells, SMC protein 1A has a granular appearance throughout the nucleus and is largely excluded from the nucleolus. SMC protein 1A reorganizes during cell division, forming puncta that align at the center of the spindle (consistent with localization to centromeres), localizing in a diffuse haze at anaphase, and reappearing in a granular distribution in the nucleus as the nucleus is reassembled.