INVESTIGATING THE DEVELOPMENTAL POTENTIAL OF TRIPLE HP1 KNOCK-OUT ES CELLS

Abstract

During the process of development, there is a limitation placed on the potential for development. The destiny of cells is flexible in the beginning stages of development; however, as the process of development continues, cells become more specialized, eventually giving rise to monopotential differentiated cells that populate adult tissues. Recent research has suggested that the cellular identity of differentiated cells is protected by an epigenetic mechanism that involves trimethylation of the ninth lysine on histone H3 (H3K9me3)-marked (hetero)chromatin. This mechanism is thought to be responsible for the safety of differentiated cells. Together with its binding partner HP1, H3K9me3 is responsible for the assembly of large heterochromatin-like domains in the euchromatic arms of chromosomes. There are three isoforms of Heterochromatin Protein 1 (HP1)which are able to bind to H3K9me3. These isoforms are HP1α, HP1β, and HP1γ. Here, we test the hypothesis that such domains regulate the identity and plasticity of the differentiated state. To that end, we will utilise our murine HP1TKO ES cells in which all three mammalian HP1 genes, encoding the HP1 isoforms HP1α, HP1β, and HP1γ are deleted. The purpose of this study is to investigate the impact that ablating HP1 function has on the capacity of HP1TKO embryonic stem cells to differentiate into mesodermal progenitors and then to keep their cellular identity after the differentiation process has been completed.