Abstract
Dinoflagellates nuclei allow for liquid crystalline characterization without core histones. In this study, nuclei were isolated from the athecate Karenia dinoflagellate species with minimum destruction to their native structure during preparation procedures. The liquid crystalline nuclei were studied by microscopy techniques of Metripol birefringence microscopy, Confocal Laser Scanning Microscopy (CLSM) and synchrotron radiation-based hard X-ray Microscopy with computed tomography, respectively. The 3D reconstruction techniques of hard X-ray tomography and CLSM were also discussed. The important biophysical parameters of the interspaces between chromosomes, nuclear surface areas and chromosome-occupied volumes were calculated from a 3D rendering of a reconstructed nucleus. The results of calculated average chromosomal DNA concentration of dinoflagellate was consistent with the concentration which can spontaneously assemble into the cholesteric liquid crystal phase in vitro.
Highlights
The cell nucleus is the natural habitat of eukaryotic genomes with multiple subnuclear compartments that structurally and functionally organized, where each chromosome is confined to a discrete region that known as chromosome territory surrounded by interspaces within spatially limited volume [1,2]
The image contrast in conventional polarizing microscopy is derived from changing the angle of polarizing light after the light is transmitted to a birefringent liquid crystalline nucleus that is between a perpendicularly orientated polarizer and the analyzer
Complementary information on the spatial distribution of intranuclear chromosomes and average chromosomal DNA concentration was obtained by combining optical microscopy and synchrotron radiation-based hard X-ray tomography, and it may aid in quantifying genome compaction of chromosomes in vivo
Summary
The cell nucleus is the natural habitat of eukaryotic genomes with multiple subnuclear compartments that structurally and functionally organized, where each chromosome is confined to a discrete region that known as chromosome territory surrounded by interspaces within spatially limited volume [1,2]. Local chromosomal DNA concentration would be valuable information for estimating intranuclear genome condensation [8]. High-resolution bioimaging of the highly condensed intranuclear organization is a challenge with current microscopy techniques because conventional light microscopy has a resolution limit of approximately half the wavelength of light, which is approximately one-fourth the diameter of a typical chromosome, and TEM micrographs of ultrathin sections of chromosomes lose information on the nuclear spatial architecture [10]. Relatively little is known about the biophysical biological aspects of intranuclear genome condensation in macromolecular crowded environment [5]
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