Abstract
Chromosome condensation is essential for the faithful transmission of genetic information to daughter cells during cell division.However, the chromosome condensation process has been still poorly understood. Here I introduce two factors, chromosome scaffold structure and divalent cations, are required for chromosome condensation. Chromosome scaffold was found in chromosome arms as an axial structure of chromosome and it has important role in chromosome construction. The scaffold structure has been observed as a single tick axis in a single chromatid. Using super-resolution microscopy and electron microscopy, I revealed that the scaffold structure mainly consists of two thin axes. It will generate stiffness and elasticity to chromosome. Although chromosome structure was severely changed without chromosome scaffold structure, chromosome condensation itself can be achieved by another factor, divalent cations. One of divalent cations, Ca2+ depletion caused defects in proper mitotic progression and chromosome condensation after the breakdown of the nuclear envelope. Fluorescence lifetime imaging microscopy-Förster resonance energy transfer and electron microscopy demonstrated that chromosome condensation is influenced by Ca2+. Ca2+ is also required for stabilization of kinetochore microtubules by loading CENP-F to kinetochore. Thus, combination of several imaging techniques is highly advantageous to understand chromosome structure.
