Graduate Program

Biological Sciences

Degree Name

Master of Science (MS)

Semester of Degree Completion

Fall 2019

Thesis Director

Gary A. Bulla

Thesis Committee Member

Antony O. Oluoch

Thesis Committee Member

Thomas Canam


In mammalian development, a complex system comprised of regulatory signals causes tissue distinction with unique structures as well as functions. Gene expression controls these functions through specific combinations of transcription factors and cofactors that influence cell differentiation by both activation and repression of genes.

Whole genome microarray studies of fibroblasts have identified candidate genes that can serve as master regulators of fibroblast identity. A previous study showed that Prrx1 and Snai2 play important roles in activating expression of fibroblast identity, and Snai2 overexpression in hepatoma cells (Fg14) activated expression of fibroblast specific genes. Moreover, Snai2 overexpression resulted in repression of liver specific genes. This thesis addresses whether Twist1 has a similar effect as Snai2. More specifically, the objective of this work is to determine how Twist1 transfection of hepatoma cells (Fg14) affects fibroblast specific and hepatoma specific genes.

qPCR analysis revealed that Twist1 was successfully over-expressed in pooled Fg14 transfectants and individual clones compared to the non-transfected cells. Following these experiments, expression of several important genes in hepatic and fibroblast function were monitored. Results show that, of the 7 fibroblast specific genes tested, Twist1 overexpression activated two genes, Prrx1 and Sema3a, in Fg14 hepatoma cells. However, the remaining 5 fibroblast genes were not affected. Twist1 overexpression was found to not affect expression of the 10 hepatoma-specific genes tested.

Based on these results, unlike results obtained with Snai2 and Prrx1 overexpression studies, Twist1 appears to have limited potential to reprogram hepatoma cells toward the fibroblast phenotype.