3D Analysis of chromosome architecture: advantages and limitations with SEM

Three-dimensional mitotic plant chromosome architecture can be
investigated with the highest resolution with scanning electron
microscopy compared to other microscopic techniques at present.
Specific chromatin staining techniques making use of simultaneous
detection of back-scattered electrons and secondary electrons have
provided conclusive information on the distribution of DNA and
protein in barley chromosomes through mitosis. Applied to
investigate the structural effects of different preparative
procedures, these techniques were the groundwork for the ``dynamic
matrix model{''} for chromosome condensation, which postulates an
energy-dependent process of looping and bunching of chromatin
coupled with attachment to a dynamic matrix of associated protein
fibers. Data from SEM analysis shows basic higher order chromatin
structures: chromomeres and matrix fibers. Visualization of
nanogold-labeled phosphorylated histone H3 (ser10) with high
resolution on chromomeres shows that functional modifications of
chromatin can be located on structural elements in a 3D context.
Copyright (C) 2005 S. Karger AG, Basel.