2013/08/06

Chromosome condensation is affected by the size of the cell nucleus

Cell Architecture Laboratory • Kimura Group

Intranuclear DNA density affects chromosome condensation in metazoans.
Yuki Hara, Mari Iwabuchi, Keita Ohsumi, Akatsuki Kimura
Mol. Biol. Cell August 1, 2013 vol. 24(15) 2442-2453 doi: 10.1091/mbc.E13-01-0043

Chromosome condensation is critical for accurate inheritance of genetic information. The degree of condensation, which is reflected in the size of the condensed chromosomes during mitosis, is not constant. It is differentially regulated in embryonic and somatic cells. In addition to the developmentally programmed regulation of chromosome condensation, there may be adaptive regulation based on spatial parameters such as genomic length or cell size. We propose that chromosome condensation is affected by a spatial parameter called the chromosome amount per nuclear space, or “intranuclear DNA density.” Using Caenorhabditis elegans embryos, we show that condensed chromosome sizes vary during early embryogenesis. Of importance, changing DNA content to haploid or polyploid changes the condensed chromosome size, even at the same developmental stage. Condensed chromosome size correlates with interphase nuclear size. Finally, a reduction in nuclear size in a cell-free system from Xenopus laevis eggs resulted in reduced condensed chromosome sizes. These data support the hypothesis that intranuclear DNA density regulates chromosome condensation. This suggests an adaptive mode of chromosome condensation regulation in metazoans.

(A) Intranuclear DNA density affects chromosome condensation. When the nucleus is smaller, metaphase chromosomes are shorter. When the nucleus contains less chromosomal DNA, metaphase chromosomes are longer.
(B) Examples of metaphase chromosomes from C. elegans samples.


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