THE EFFECT OF MATRIX RIGIDITY ON HISTONE MODIFICATIONS DURING EPITHELIAL TO MESENCHYMAL TRANSITION

Open Access
Author:
Blanchard, Paul Legendre
Area of Honors:
Chemical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Esther Winter Gomez, Thesis Supervisor
  • Darrell Velegol, Honors Advisor
Keywords:
  • Epithelial to Mesenchymal Transition
  • Extracellular Matrix Stiffness
  • Histone Methylation
  • TGF-Beta
  • JMJD2A
Abstract:
Epithelial to mesenchymal transition (EMT) is a process in which an epithelial cell loses its cell-cell adhesion and polarity, and instead gains mesenchymal traits, such as mobility. The human body uses EMT to produce myofibroblasts, which aid in wound healing. However, aberrant activation of EMT to produce myofibroblasts can contribute to fibrosis and cancer progression. One of the pathways that can initiate EMT is through Transforming Growth Factor (TGF)-β1, the effect of which has been shown to change with matrix rigidity. TGFβ1 will induce EMT in cells grown on stiff matrices, but not when grown on soft matrices. The purpose of this research was to determine why this stiffness regulation might occur by determining the role histone modifications play. Histone modifications are chemical modifications that occur on histones, proteins that wrap DNA into chromatin, which regulate what genes are expressed. Levels of one specific marker, the trimethylation of lysine 36 on histone H3 (H3K36Me3) were shown to increase with increasing rigidity after TGFβ1 treatment, suggesting that it may be involved in the matrix stiffness regulation EMT. Treatment with cell contractility inhibitors resulted in a decrease in the aforementioned histone marks in cells cultured on the stiff gels, which may indicate that increased cell contractility contributes to the way that stiffness regulates histone modifications during EMT. Initial studies of JMJD2A, a demethylase protein which removes a methyl group from histones, indicate that JMJD2A levels increase with increasing rigidity and TGF-β1 treatment. Furthermore, inhibition of demethylases results in a decrease in the expression of the mesenchymal marker alpha smooth muscle actin (aSMA), suggesting that demethylases play an important role in regulating EMT. Additional studies are needed to confirm mechanistically how JMJD2A and the histone mark H3K36Me3 contribute to EMT.