Doctoral Dissertations

Date of Award

12-2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Biochemistry and Cellular and Molecular Biology

Major Professor

Rachel Patton McCord

Committee Members

Keerthi Krishnan, Francisco Barrera, Mariano Labrador, Bruce McKee, Christopher Baker

Abstract

Cells in our body experience constant mechanical forces that influence biological functions such as growth and development. The nucleus has been implicated as a key mechanosensor and can directly influence chromatin organization and epigenetic alterations leading to gene expression changes. However, the mechanism by which such mechanical forces lead to genomic alterations and expression of mechanosensitive genes is not fully understood. The work presented in this dissertation investigates the effect of mechanical and epigenetic perturbations on the 3D genome organization. To investigate this 3D genome folding, we use Chromosome Conformation Capture followed by high throughput sequencing (Hi-C) (Chapter-1) which identifies a hierarchical organization of the genome to ensure proper gene regulation. We then investigate how this non-random 3D genome organization is affected when cancer cells undergo compressive and tensile forces induced by migration through constricted spaces (Chapter-2) and the pre-existing structural patterns that may enable such dramatic nuclear deformations (Chapter-3). Chapter 4 includes a detailed characterization of structural patterns associated with global decompaction of the chromatin, which has been shown to modulate nuclear mechanical properties. Lastly, Chapter-5 characterizes the effect of mechanical stretching of cells on the 3D genome structure. Overall, these findings provide evidence about the role of the 3D genome organization in ability of cells to withstand mechanical perturbations by not only regulating transcriptional networks but also aiding as a protective barrier from such forces that could jeopardize the nuclear integrity.

Movie_S1_Top5_2DMigration.avi (6507 kB)
Phase contrast live cell imaging in a 2D culture dish of a Top-5 cell

Movie_S2_Bottom5_2DMigration.avi (3992 kB)
Phase contrast live cell imaging in a 2D culture dish of Bottom-5 cells

Movie_S3_Top5_3D_nuclear_rendering_final.avi (3669 kB)
3D rendering of Top-5 nucleus using Leica Sp8 software

Movie_S4_Bottom5_3D_nuclear_rendering_final.avi (4086 kB)
3D rendering of Bottom-5 nucleus using Leica Sp8 software

Movie_S5_Top5_3D_Collagen_Migration.avi (7155 kB)
Live time-lapse imaging of Top-5 cells migrating through 3D collagen matrices

Movie_S6_Bottom5_3D_Collagen_migration.avi (4584 kB)
Live time-lapse imaging of Bottom-5 cells migrating through 3D collagen matrices

Movie_S7_Top5_3DCollagen_nuclear_rendering_final.avi (3593 kB)
3D rendering of nucleus of collagen embedded Top-5 cell

Movie_S8_Bottom5_3DCollagen_nuclear_rendering_final.avi (3511 kB)
3D rendering of nucleus of collagen embedded Bottom-5 cell

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