Date of Graduation

Fall 5-22-2015

Document Type

Thesis

Degree Name

Master of Science in Biology

College/School

College of Arts and Sciences

Department/Program

Biology

First Advisor

Dr. Christina Tzagarakis-Foster, Ph.D.

Second Advisor

Dr. James Sikes, Ph.D.

Third Advisor

Dr. Cary Lai, Ph.D.

Abstract

DAX-1, an orphan nuclear hormone receptor, acts mainly as a repressor through transcriptional protein complexes. Its unique structure and specific expression raises questions as to what its precise interactions are and how it mediates its repressive function. While it is known to play a role in sexual development and adrenal insufficiency, expression in certain types of cancer suggests additional functions and interactions. Knock in of DAX-1 into a low-DAX-1 expressing cancer cell line has been previously observed to increase apoptosis, while, inversely, down in a high-DAX-1 expressing cancer cell line shows a decrease in apoptosis. Target genes that belong to the TNFα and BCL-2 families have shown changes in expression correlating to the modified levels of DAX-1 in knock-down experiments. Direct regulation of BCL-2, one of the target genes of interest, was investigated further based on mirrored expression changes of DAX-1 in knock-down and knock in experiments through ChIP experiments. These findings emphasize a significant role of DAX-1 in moderating apoptosis in a breast cancer cell line.

In the context of undifferentiated mouse embryonic stem cells, Dax-1 is highly expressed and has been shown to be an important contributor to the pluripotent state. Potential downstream targets of Dax-1 were previously identified based on significant changes in expression when Dax-1 expression was down regulated. Two methods, siRNA and CRISPR-Cas9, were used to decrease Dax-1 expression in the E14 mouse embryonic stem cell line. Direct interactions and other novel stem cell factors were confirmed using analysis of publically available ChiP-seq data. Ultimately, while Dax-1 is not a master regulator, its transcriptional control of specific genes that are key in the maintenance of pluripotency is an important component of stem cell growth and differentiation. Bioinformatic analysis of ChIP-seq experiments brought to light general patterns as to how Dax-1 contributes to pluripotency, and additional ontologies of Dax-1 target genes for future studies.

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