Characterization of UHRF1 expression in human induced pluripotent stem cells and in UHRF1 conditional knockout models

Abstract

UHRFl (ubiquitin-like protein, containing PHD and RING finger domains 1) is essential in epigenetic modification and cell cycle progression. In vivo knockdown of UHRF1 is lethal and embryogenesis does not progress to produce viable knockout models. In this study, Cre recombinase adenovirus is used to generate an in vitro knockdown of UHRF1 in Mouse Embryo Fibroblasts. The study also proposes the use of Albumin-Cre mouse model and Cre-lox technology to make conditional UHRF1 knockdown in the liver. These models will prove to be essential in further experiments to understand the precise role of UHRF1 and its homologs. Unlike in non-mammals, a number of UHRF1 homologs have been identified in mammals but their exact function is disputed. This study measures the mRNA expression of UHRF1 and UHRF2 in human induced pluripotent stem cells as they differentiate into hepatocytes and show that mRNA expression of UHRF2 is significantly higher in differentiated cells as compared to the expression of UHRF1. There have been studies that show UHRF 1 expression at various cell cycle phases, but there is little known about the regulation of UHRF1 itself. To further understand the relation between DNA methylation and UHRFl expression, this study shows that hypomethylation of DNA with methylation inhibitor, 5-Azacytidine, induces an increase in UHRF1 expression, suggesting that UHRF1 not only regulates the gene expression by DNA methylation but may also play a role in self-regulating its own expression.