Cloning in Cattle [thesis]

Daniela Koehler
In mammalian cell nuclei chromosome territories (CTs) occupy positions correlating with their gene-density and chromosome size. While this global radial order has been well documented, the question of whether a global neighborhood order is also maintained has remained a controversial matter. To answer this question I grew clones (of HeLa, HMEC and human diploid fibroblast cells) for up to 5 divisions (32 cells) and performed 3D FISH experiments to visualize the nuclear positions of 3 different
more » ... ons of 3 different CT pairs. Using different landmark-based registration approaches I assessed the similarity of CT arrangements in daughter cells and cousins. As expected from a symmetrical chromatid movement during mitotic anaphase and telophase, I was able to confirm previous findings of a pronounced similarity of CT arrangements between daughter cells. However, already after two cell cycles the neighborhood order in cousins was nearly completely lost. This loss indicates that a global neighborhood order is not maintained. Further, I could show in the present thesis that a gene density correlated distribution of CTs, which has already been shown in different cell types of various species appears to be independent of the cell cycle. Moreover I could provide evidence that the nuclear shape plays a major role in defining the extent of this gene-density correlated distribution, as nuclei of human, old world monkey and bovine fibroblasts showed an increased difference in the radial distribution of gene poor/dense CTs when their nuclei were artificially reshaped from a flat ellipsoid to a nearly spherical nucleus. The observation that a gene-density correlated distribution of CTs has been found in nuclei from birds to humans argues for a significant, yet undiscovered functional impact. So far CTs have been investigated mainly in cultured cells and to some extent in tissues, yet little is known about the origin and fate of CTs during early development. To gain insights into the very early organization of CTs in preimplantation embryos I have deve [...]
doi:10.5282/edoc.9915 fatcat:6by3tid3bzgjfcwtgrpoajebhm