Abstract:
Cells in the human body are exposed to a wide range of stimuli, often simultaneously. In order to survive, cells must mount cell-type-, context-, and stimuli-specific responses, which can be modulated by genetic variation. The nucleus plays an important role in integrating these extracellular signals, and producing the appropriate cellular changes. In this thesis I investigate chromatin and transcriptional changes that occur in an acute myeloid leukemia cell line (HL-60/S4) after treatment with mechanical and chemical stimuli. I migrated neutrophil-like cells through a confined space to test the effects of mechanical stimulus on the nucleus. I found that cellular remodeling is associated with disruption to the organization of silent chromatin, while transcriptional programs seem largely undisturbed by migration with constriction. Treatment of undifferentiated and neutrophil-like cells with the proinflammatory cytokine TNF-a identified cell-type-specific responses to chemical stimulus. Divergent transcriptional responses were identified in the two cell types, characterized by upregulation of cell cycle genes in undifferentiated cells, and repression of the same genes in neutrophil-like cells. Comparisons to publicly available data characterized the genome structures of two versions of the HL-60 cell line, to gain insight into the reproducibility of experiments performed in this cell line. Multiple samples of HL-60/S4 have highly consistent genomic architectures. However, different sources of the original HL-60 cell line have a small number of disparities in their cytogenetic information. In conclusion, a crucial role of nuclear architecture is to enhance the response to critical stimuli, while minimizing the response to irrelevant signals.