Qiao Zhou - US grants

Cellular reprogramming has emerged in recent years as a promising approach in regenerative medicine whereby abundant adult cells ofthe body are converted into medically important cell types to repair tissues lost due to disease or injury. This approach could prove valuable for developing treatments for Type 1 diabetes, a disease that results from autoimmune destruction of insulin secreting beta cells. The long term goal of this proposal is to understand the cellular and molecular mechanisms that control beta cell reprogramming. We will take advantage of a recently developed model system where a small number of transcription factors reprogram adult exocrine cells into beta cells. In Specific Aim I, we will determine the functional contribution of each reprogramming factor to the beta cell reprogramming process. In Aim II, we will determine the functional and physical interactions between reprogramming factors and chromatin remodeling genes. In Aim III, we will determine whether exocrine identity genes act as molecular barriers to beta cell reprogramming. The proposed studies are expected to shed important light on the molecular mechanisms that control beta cell reprogramming. Such molecular insights will allow better control ofthe reprogramming process and aid the development of novel cell replacement therapies to treat Type 1 diabetes.

? DESCRIPTION (provided by applicant): One major goal of regenerative medicine is to produce insulin secreting ?-cells for transplantation therapy to treat Type 1 diabetes (T1D). Differentiation of embryonic stem cells is a powerful technology to generate functional insulin+ cells. However, teratoma formation is a serious concern with this approach. Alternatively, adult tissues could be converted into insulin+ cells in a process termed reprogramming. Reprogramming adult cells carries little risk for teratoma, but the reprogramming efficiency tends to be low and the resulting insulin+ cells have limited functionality. There is a critical ned to define the best tissue source and reprogramming method for this approach. My laboratory pioneered a reprogramming method based on a cocktail of defined genetic factors (Ngn3, Pdx1, Mafa, referred to as NPM factors). NPM factors are sufficient to convert pancreatic acinar cells to stable and functional insulin+ cells in animal models. In a comprehensive screen of adult tissues, we discovered that cells residing in the adult gastric mucosa also respond rapidly to NPM factors and generate functional insulin+ cells. Significantly, gastric insulin+ cells become glucose responsive faster than acinar-derived insulin+ cells. Thus, gastric tissue is a highly promising adult tissue source to produce functional insulin+ cells. Importantly, human gastric cells can be cultured and propagated as organoids in large numbers from cadaveric sources. Delivery of NPM factors led to formation of c-peptide+ cells in the human organoids, raising the exciting possibility of generating functional human insulin+ cells with this approach. One major aim of the proposal is to gain deeper understanding of the reprogramming process and the resulting gastric insulin+ cells. Specifically, we will determine the molecular and functional similarity of the induced gastric insulin+ cells with native islet beta-cells. We will investigate stability of the induced cells and test the hypothesis that islet structure formation will lead to heir long-term stability. We will also define the individual function of NPM factors in the reprogramming process. The second major aim of the proposal is to develop methods for efficient induction of functional insulin+ cells from human gastric tissues with combined treatment of genetic factors and signaling pathway modulators. Together, these studies will provide the necessary foundation for developing a novel technology to produce functional human insulin+ cells for therapeutic transplantation.

PROJECT SUMMARY Transplantation of insulin-secreting beta cells is an effective therapy for Type 1 diabetes (T1D). To secure supplies of these therapeutic cells, many research groups are actively optimizing protocols to derive insulin+ cells by differentiation of human embryonic stem cells (hESCs) or by reprogramming of adult tissues. The next major challenge is to discover methods to protect transplanted cells from autoimmunity to achieve long-term glycemic control. Clinical observations have long suggested existence of beta cells in T1D patients that escape autoimmunity and continue to function. Such cells are very challenging to study from clinical samples. New research tools are needed to address the critical question of how to produce insulin-secreting cells that resist autoimmunity. Our laboratory recently discovered that insulin-secreting cells can be readily produced from murine gastric tissues using a direct reprogramming approach with defined genetic factors Ngn3, Pdx1, and Mafa (referred to as NPM factors). The gastric-derived insulin+ cells share key molecular and functional features of pancreatic beta cells but are not identical to native beta cells. We transplanted gastric insulin+ cells into the NOD murine model of T1D and made the surprising observation that gastric insulin+ cells, unlike native pancreatic beta cells, are not subject to strong immune attack, suggesting reduced immunogenic properties. This observation raised the exciting possibility that gastric-derived insulin+ cells could be employed as a novel tool to study immune-beta cell interactions in human T1D and may be further developed into a transplantation therapy that requires minimal immune protection. In this proposal, we will develop new methods to produce functional insulin-secreting cells from human gastric tissues using two separate approaches and study their immunogenic properties with a variety of tools including human T1D- derived T-cell clones. Our ultimate goal is to gain mechanistic insight into the immune response to beta cells in T1D and to discover novel pathways that may diminish or prevent the autoimmune attack. If successful, this project will also lay the foundation for a novel source of insulin-secreting cells for therapeutic transplantation to treat T1D.

PROJECT SUMMARY The colon is a major segment of the intestine and differs significantly from the small intestine in morphology, cell types, physiological function and disease susceptibility. Devastating and prevalent diseases, including colorectal cancers and ulcerative colitis, arise from colon but not small intestine. Colon absorbs water but cannot uptake most nutrients like the small intestine and consequently a significant loss of the small intestine will lead to digestive failure that the colon cannot compensate. Despite significant progress, aspects of the colon biology remain poorly understood. Molecular determinants that distinguish the colon from the small intestine and govern colon-specific cell lineage differentiation and homeostasis remain largely uncharacterized, hindering a deeper understanding of regionalized intestinal diseases. In preliminary studies, we identified SATB2, a chromatin factor with restricted expression in the colonic epithelium, as a crucial molecular regulator of colon identity and differentiation. SATB2 deletion from adult intestine led to a homeotic-like transformation of colonic epithelium into one that resembles small intestine ileum in cellular composition and gene expression, and the mutant colon can absorb nutrients, a function unique to the small intestine. These data suggest that SATB2 is a potential ?master regulator? of colonic epithelium. The identification of SATB2 offers a unique opportunity to study colonic ontogeny and fate determination, and assess its therapeutic implications. In this project, Aim 1 will evaluate the hypothesis that colonic stem cells harbor primed ileal enhancers and thus harbor a chromatin-level permissiveness for ileal transcriptional activation and cell fate plasticity. Aim 2 studies will evaluate the hypothesis that SATB2 recruits two chromatin remodeling factors, MTA2 and SMARCD2, to separate pools of colonic and ileal enhancers to modify local chromatin, allowing differential access of intestinal transcription factors and effecting transcriptional regulation. In Aim 3, using mouse models of Short bowel syndrome (SBS), we will evaluate whether promoting colonic nutrient absorption can combat digestive failure and the associated pathophysiology in SBS. These studies together will elucidate the cellular and molecular mechanisms by which SATB2 preserves colonic identity and effects a colonic to ileal conversion, which may be exploited as a novel therapeutic approach to treat SBS.