Investigation of the biophysical basis for cell organelle morphology

• Main Author: Mayer, Jürgen
• Other Authors: Technische Universität Dresden, Fakultät Mathematik und Naturwissenschaften
• Format: Dissertation
• Language: English
• Published: Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden 2010
• Subjects: morphology; nucleus; shape energy; bending energy; shape analysis; Fourier series; Fourier coordinate expansion; data reduction; elliptic approximation; harmonic truncation; pareto optimality; Helfrich-Canham free energy; fission yeast; microtubules; Schizosaccharomyces pombe; mitosis; confocal microscopy; image analysis; Morphologie; Zellkern; Konturenergie; Biegeenergie; Formanalyse; Fourier-Serien; Koordinatenweise Fourier-Entwicklung; Datenreduktion; elliptische Näherung; harmonische Analyse; pareto-Optimierung; freie Energie nach Helfrich und Canham; Mikrotubuli; Mitose; konfokale Mikroskopie; Bildanalyse; ddc:570; rvk:WD 2300; rvk:WC 7000; rvk:WE 5300
• Online Access: http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-26600; http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-26600; http://www.qucosa.de/fileadmin/data/qucosa/documents/2660/DiplomaThesis_JuergenFinalVersion.pdf

It is known that fission yeast Schizosaccharomyces pombe maintains its nuclear envelope during mitosis and it undergoes an interesting shape change during cell division - from a spherical via an ellipsoidal and a peanut-like to a dumb-bell shape. However, the biomechanical system behind this amazing transformation is still not understood. What we know is, that the shape must change due to forces acting on the membrane surrounding the nucleus and the microtubule based mitotic spindle is thought to play a key role. To estimate the locations and directions of the forces, the shape of the nucleus was recorded by confocal light microscopy. But such data is often inhomogeneously labeled with gaps in the boundary, making classical segmentation impractical. In order to accurately determine the shape we developed a global parametric shape description method, based on a Fourier coordinate expansion. The method implicitly assumes a closed and smooth surface. We will calculate the geometrical properties of the 2-dimensional shape and extend it to 3-dimensional properties, assuming rotational symmetry. Using a mechanical model for the lipid bilayer and the so called Helfrich-Canham free energy we want to calculate the minimum energy shape while respecting system-specific constraints to the surface and the enclosed volume. Comparing it with the observed shape leads to the forces. This provides the needed research tools to study forces based on images.