Objective
With support from the JDRF, we propose to carry out cellular and molecular experiments to understand how T cells expressing the master regulator transcription factor, Zbtb20, function. In doing so, we propose to harness their regulatory activity to create a new cellular therapy for T1D. In mice, we will test different models of diabetes to study how the cells respond. Next, we will determine if T cells genetically modified to express Zbtb20 can protect mice from T1D. Finally, we will work to understand the regulation of expression of Zbtb20 as means to therapeutically control in vivo expression
Background Rationale
It has been known for many years that Type 1 diabetes (T1D) is an autoimmune disease that is a result of chronic inflammation of islets, leading to the destruction of insulin producing beta cells. If the inflammation in the pancreas can be controlled, much of the damaging immune response should be held in check. This same principle is true for other tissues, including the excessive immune response that causes inflammatory bowel diseases like Crohn’s and colitis. The immune system is very complex - many different cell types and proteins are involved in controlling inflammation. Our recently published studies offer a key new insight into this process. We have identified a new type of T cell that is distinct from others in many ways. Of key importance, we have also determined the master regulator transcription factor that controls these cells. We show that if this transcription factor is missing, spontaneous inflammation occurs in the intestine. The damage that occurs makes mice extremely susceptible to severe colitis.
We now know that these same regulatory T cells are found in the pancreas. Therefore, it is reasonable to hypothesize that if these cells do not function properly, spontaneous inflammation might also occur in this organ. This inflammation may lead to T1D. Additionally, we have shown that adoptive transfer of T cells expressing the master regulator transcription factor can prevent inflammation, thereby suggesting a new type of therapeutic. These ideas will be studied with support of JDRF.
Description of Project
The immune system is a network of many different cell types. Each type of cell has a different function for keeping us healthy. Each cell type must respond at the correct time and in the correct way to prevent disease. This diversity and specialization of cell function is at the core of the research done by the Sant’Angelo laboratory. Our goal is to define “master regulator” genes, known as transcription factors, that control the primary functions of immune cells.
We have learned that many immune cells are “hardwired” to do specific jobs. The hardwiring comes from the genes the cells express. The most important genes – the master regulators - are key because they determine exactly what other genes should be used. In turn, it is these genes that determine what a cell can do. Should the wrong genes be turned on or off, a potentially protective cell can cause damage to tissues.
Published data suggests that immune cells that protect our tissues and organs by controlling inflammation in a process termed “immune homeostasis”. Sometimes immune cells lose the capacity to prevent inflammation, and this can cause disease. While scientists understand that this can happen, it has been complicated to control the process because the precise cells of the immune system that are involved are not known. Our new data may have solved the problem of exactly which cells control inflammation. We have discovered a new type of T cell that expresses a master regulator transcription factor called Zbtb20. So far, we have only studied these new T cells in the intestine, but we now know that Zbtb20 T cells are in the pancreas of young mice and their numbers appear to increase with age. What we know is that mice that do not have Zbtb20 T cells in the intestine have disrupted tissue homeostasis. In other words, there is spontaneous inflammation which damages the intestine. This damage makes the mice very susceptible to inflammatory bowel disease. The disease is so bad that many of the mice die.
In preliminary data for this application, we show that Zbtb20 T cells are also in the pancreas and appear to increase as mice age. The research plan described in this application proposes experiments that will determine the function of Zbtb20 T cells in the pancreas in NOD mice. Additionally, since Zbtb20 is the master regulator of these cells, we propose that these protective functions are transferable to conventional T cells which creates the potential of a cellular therapy for these chronic diseases. We have produced multiple new tools, key datasets, and essential data both from mice and humans to enable us to pursue these innovative ideas and approaches to treat T1D.
Anticipated Outcome
Ultimately, if our research is successful, we will have identified a new type of regulatory T cell that is involved in T1D pathogenesis. We anticipate that this cell is functionally or numerically deficient in the NOD mouse and, potentially in people who have or are susceptible to the disease. The goal, therefore, would be to correct immune system function by restoring the effective ZBTB20 T cell mediated control of inflammation. Proposed studies in this application would lay the groundwork by determining if adoptive transfer of additional Zbtb20 T cells delays disease onset. Furthermore, we will learn if Zbtb20 T cells can be created in vitro by transduction with the gene, which would enable large numbers of the cells to be produced for cellular therapy treatments. We also seek to understand the regulation of ZBTB20 expression, which will create opportunities to directly control gene expression in vivo.
Relevance to T1D
We have shown that a new type of regulatory T cell that we have recently discovered is essential for tissue homeostasis in the intestine. Absence of these T cells, we show, make mice highly susceptible to disease. Importantly, we also show that reconstitution of mice with function cells restores the mice to health. We now find that this new type of T cell is also present in the pancreas. We hypothesize that these cells do not function properly in mice and people prone to T1D. Furthermore, we propose that transfer of functional versions of these T cells can be a means to prevent, delay or cure T1D. Our research is, therefore, directly relevant for the identification of a potential cause and/or treatment of T1D.