ABSTRACTS GRADUATE STUDENTS

Underlying Mechanisms of Ubiquitin Specific Peptidase 2 (Usp2) Isoforms’ Regulation in Hepatocellular Carcinoma by the Farnesoid X Receptor (Fxr) Signaling Pathway

Winifer Ali, Xinmu Zhang, Syed Hashmi, Qiwen Chen, Ruitang Deng

Ubiquitin specific peptidase 2 (USP2) is a deubiquitinating enzyme known to modulate cell cycle progression, circadian rhythm, and carcinogenesis in the liver. USP2 and its isoforms USP2a and USP2b are dysregulated in human hepatocellular carcinoma (HCC) tissues and farnesoid x receptor knockout (FXR-KO)-HCC mouse models. However, the mechanism by which FXR regulates USP2 isoforms and its contribution to the pathogenesis of HCC is largely unknown. In this study, we discovered that USP2a and USP2b are derived from separate promoters and are specifically regulated by ligand-activated FXR. Our in vivo studies revealed that USP2a and USP2b expression is significantly increased in obetocholic acid (OCA)-treated wild-type (WT) mice and have no change in FXR-KO mice compared to vehicle treated groups. In our in vitro studies, we discovered that the FXR isoform FXRα2 predominantly transactivated USP2a and USP2b promoter activity in Huh7 cells. In silico analysis of USP2a and USP2b promoters in bioinformatic predictions revealed novel USP2a and USP2b-FXR response elements (FXREs). Targeted mutagenesis of the novel FXREs completely abolished inducibility of the USP2a and USP2b promoters in FXR agonist OCA-treated Huh7 cells. Electrophoretic mobility shift assays (EMSA) and chromatin immunoprecipitation (ChIP) demonstrated direct binding and abundant recruitment of FXR and its coregulators to the human and mouse USP2a and USP2b promoters. Overall, this study has established the correlation between the expression of USP2 isoforms and their direct regulation by FXR in the pathogenesis of HCC. Most importantly, this novel mechanism provides the molecular basis for developing therapies to treat HCC through modulating USP2a and USP2b expression by FXR activation.

The role of epigenetics in age-related cognitive decline and Alzheimer's disease

Sydney Bartman, Lauren Gaspar, Hannah Tobias-Wallingford, Danielo Zamor, Giuseppe Coppotelli, Jaime M. Ross

Recent decades have witnessed a dramatic increase in human longevity, which has contributed to higher prevalence of age-related diseases including brain aging disorders, such as Alzheimer’s disease (AD). The aging process is accompanied by an accumulation of damage to macromolecules, organelles, and cells, which ultimately leads to organ/tissue dysfunction and death. Although the precise cause of the aging process is unknown, epigenetic alterations and deregulation of gene expression have been implicated in playing a role. Using the innovative ICE (inducible changes to the epigenome) mouse model together with the well-characterized APP/PSEN1 (APP/PS1) mouse, we are directly testing, for the first time, whether epigenetic alterations induced by DNA damage, can affect the onset and progression of AD pathology in “DICE” (dementia from inducible changes to the epigenome) mice. A battery of behavioral testing is ongoing to compare possible cognitive changes in DICE mice with APP/PS1/CRE, ICE, and CRE controls. Preliminary results thus far indicate that male and female DICE mice move significantly more and with faster speed than controls, when assessing spontaneous locomotion in the open field behavioral assay. Using the startle reflex behavioral assay to evaluate brainstem functioning, both male and female DICE mice demonstrated a larger motor response following various auditory stimuli, as compared to controls. Ongoing studies aim to characterize and quantify A� plaque formation as well as gliosis and microglial expression in brains from DICE mice as compared to APP/PS1/CRE controls using immunohistochemistry, western blot, ELISA, and qPCR. These findings will provide valuable insights into the etiology of Alzheimer’s disease, especially as it pertains to the role of epigenetics.