Author ORCID Identifier

http://orcid.org/0000-0003-3217-848X

Year of Publication

2016

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Medicine

Department

Microbiology, Immunology, and Molecular Genetics

First Advisor

Dr. Brett T. Spear

Abstract

The Spear lab has had a long-standing interest in gene regulation in the liver during development and disease. Several years ago, these studies identified a novel transcriptional regulator called Zinc fingers and homeoboxes 2 (Zhx2), which is a member of a small family that includes Zhx1 and Zhx3. All Zhx proteins contain two amino-terminal C2-H2 zinc fingers and four or five carboxy-terminal homeodomains. Previous studies indicate that Zhx proteins can form homodimers and heterodimers with each other.

Zhx2 regulates numerous hepatic genes, including alpha-fetoprotein (AFP) and H19. Genes controlling lipid and cholesterol homeostasis are also regulated by Zhx2. More recently, our lab has found that a number of Cytochrome P450 (Cyp) genes and Major urinary protein (Mup) genes are also targets of Zhx2. The BALB/cJ mouse substrain contains a natural hypomorphic mutation in Zhx2, and the aforementioned targets are dysregulated in the livers of adult BALB/cJ mice. Recently, our lab developed mice that contain a floxed allele of Zhx2. By crossing these mice with transgenic mice that express the Cre recombinase in all tissues or in hepatocytes, we can knock-out Zhx2 expression in all tissues or solely in the liver, respectively.

Much of the research in the Spear lab has focused on the role of Zhx2 in liver gene expression during development and several models of liver disease. However, we have found that Zhx2 is ubiquitously expressed in all adult mouse tissues. The first part of my project has utilized whole-body Zhx2 knock-out mice to investigate the role of Zhx2 in various tissues, including kidney, brain, small intestine, liver, salivary and lacrimal glands. These studies indicate that some, but not all, previously identified Zhx2 targets are also regulated by Zhx2 in non-liver tissues. I have also carefully evaluated whether the absence of Zhx2 results in increased perinatal lethality and/or altered postnatal growth. These studies suggest that postnatal growth of male Zhx2 knock-out mice is delayed compared to wild-type Zhx2 littermates.

My second project examined subcellular localization of Zhx proteins. To accomplish this, GFP-Zhx fusion proteins were expressed in transfected cells. Zhx1 and Zhx2 localized to the nucleus whereas transfected Zhx3-GFP proteins were found in both the nucleus and cytoplasm. Moreover, when Zhx3-GFP was co-transfected with Zhx2, Zhx3-GFP was found strictly in the nucleus. This data suggests that interactions between Zhx proteins could alter protein localization. I employed bioinformatics tools to predict the 3D structures of Zhx1, Zhx2, and Zhx3 monomers, homodimers, and heterodimers.

Digital Object Identifier (DOI)

https://doi.org/10.13023/ETD.2016.515

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