Chromosome territory position and active relocation in normal and hutchinson-gilford progeria fibroblasts

Abstract

Radial chromosome positioning in interphase nuclei is non-random and can alter according to developmental, differentiation, proliferation or disease status. The aim of this thesis is to understand how chromosome re-positioning is elicited and to identify the nuclear structures that assist this re-localisation event. By positioning all human chromosomes in primary fibroblasts that have left the proliferative cell cycle, the study within this thesis has demonstrated that in cells made quiescent by reversible growth arrest, chromosome positioning is altered considerably. Upon removal of serum from the culture medium, chromosome re-positioning took less than 15 minutes, required energy and was inhibited by drugs affecting the polymerization of myosin and actin. The nuclear distribution of nuclear myosin 1β was dramatically different in quiescent cells as compared to proliferating cells. If the expression of nuclear myosin 1β was suppressed using interference RNA procedures the movement of chromosomes after 15 minutes in low serum was inhibited. When high serum was restored to the serum starved cultures chromosome repositioning was only evident after 24-36 hours that coincided with a return to a proliferating distribution of nuclear myosin 1β.