Lauren B. Tolliver
Francesca DiFurio, Ph.D.
Project: Mechanisms of Hepatocyte Differentiation from Human Pluripotent Stem Cells
My project has focused on using human induced pluripotent stem (iPSC) cells to identify the mechanisms that control human hepatocyte fate. I have been focusing on the role of two transcription factors, HNF1B and HNF4A, in defining a transcription factor cascade that drives the conversion of the endoderm to a liver cell fate. My project relies heavily on genome engineering (Crispr-CAS9) and genome-wide analyses such as RNA-Seq and ChIP-Seq to dissect the molecular mechanisms through which these transcription factors establish cell character.
James Heslop, Ph.D.
Project: Molecular Basis of Human Hepatocyte Formation
Human liver development is incompletely understood. In part, this is due to the lack of available material to study the complex processes of differentiation, with most of our current understanding derived from mouse models. The recent establishment of protocols which allow for the scalable, reproducible and manipulatable differentiation of human induced pluripotent stem cells to hepatocyte-like cells has allowed for researchers to investigate human liver development in a dish. My projects focus on some of the earliest stages of differentiation, investigating the role of the GATA family of transcription factors during endoderm formation and the role of FGF signalling in hepatic specification. Both of these pathways have been shown to be essential for liver development, but the exact mechanisms which underlie their importance requires further investigation.
Ray Jui-Tung Liu, Ph.D.
Project: Identification of Small Molecules to Enhance the Formation of Hepatocytes From iPSCs
My project is using novel high throughput reporter assays to identify pathways that regulate hepatocyte maturation. We have generated human iPSC-lines that express secreted reporter proteins from genes that are characteristic of mature hepatocytes. We are using these cell lines to identify small molecules that impact the efficiency of differentiation. These studies will provide novel insight into the mechanisms that control hepatocyte maturation as well generate new procedures to efficiently produce human hepatocytes from stem cells.
PhD Program, Biomedical Science
Project: Identification of Novel Cellular Process that Control Hepatic Cell Fate
I joined the Duncan lab to gain experience in using induced pluripotent stem cells to study liver disease and development. Liver disease includes a broad range of disorders including those affecting metabolism, cholesterol production, and carbohydrate metabolism as well as infectious diseases, cirrhosis and fibrosis, and fatty liver disease such as NASH. In my project I have been using small molecule screens to identify pathways that affect the formation and function of hepatocytes. One pathway that I have focused on is that mediated by HSP90, which appears to be important for the expression of transcription factors that are key regulators of hepatic function. My project uses a wide variety of tools including drug screening, genome engineering, stem cell culture, and cell imaging as well a battery of molecular biology approaches.
Behshad Pournasr, Ph.D.
Project: Modeling Organic Acidemias Using Genome Engineering of Human iPSCs
I am interested in using iPSC-derived hepatocytes as a platform to identify new therapeutics to treat metabolic liver disease. My main project in the Duncan lab is to model a series of diseases that affect amino acid metabolism called organic acidemias. These are rare and serious diseases that are caused by mutations in enzymes that regulate metabolism of branched-chain amino acids primarily in the liver. If untreated, patients suffer a build up of ammonia and progressive encephalopathy. I am using CRISPR-Cas9 to introduce mutations into human iPSCs that recapitulate those found in patients. The iPSCs will be induced to differentiate into hepatocytes to model the acidemias in culture. I propose that generating a cell culture model of these acidemias will allow us to produce a platform for drug discovery that will allow us to treat individuals with these diseases.
Graduate Student PhD Program, Biomedical Science (MCW)
Project: Defining the Molecular Mechanisms Underlying the Endoderm to Hepatic Transition
As an undergraduate studying Biomedical Engineering and Physics at Columbia University, I conducted research on determining the proper substrate rigidity in order to activate mouse naïve CD4+ T-cells. It was here that I became interested in pursuing a career within biomedical research. I joined the lab of Dr. Stephen Duncan in the Department of Regenerative Medicine and Cell Biology. The focus of the Duncan lab is to study liver development and function by utilizing induced pluripotent stem cell technology. One aspect of my project is to understand the role that BMP4 and SMAD proteins play in regulating differentiation of hepatocytes. Another faction of my project is to model and understand various liver disease phenotypes by creating patient specific hepatocytes. This is done by obtaining patient specific fibroblasts and reprogramming these cells into iPS and subsequently differentiating these iPS cells into hepatocyte-like cells, which provide a ‘disease-in-a-dish’ model that can be used for drug discovery.