Defining GATA4’s Molecular Function in Gastric Cell Biology

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SUMMARY Gastric parietal cells (PCs) play a critical role in GI function by secreting acid for digestion and protection against infection and by synthesizing growth factors that influence the development of other cell types including zymogenic chief cells. Although there has been longstanding interest in defining PC biology and gastric acid secretion dating back to the 1800s, PCs have been challenging to study. PC dysfunction, including acid hypersecretion or hyposecretion, underlies a range of human diseases associated with a high socioeconomic burden including chronic gastritis, drug-related peptic ulcer disease, Helicobacter pylori related peptic ulcer disease, and cancer. For example, peptic ulcer disease affects more than 4 million people in the US each year with 1 in 10 persons experiencing an ulcer at least once, and gastric cancer is the third leading cause of cancer related deaths worldwide. Given the essential role for PCs in maintaining a healthy stomach, it is surprising that a comprehensive understanding of the molecular programs that regulate and maintain normal PC differentiation and function, and thereby PC health and overall gastric epithelial cell health, is incomplete. Our finding that the transcription factor GATA4 binds to the regulatory regions—enhancers and promoters—of 81% of gene set defined as being uniquely expressed in PCs sheds light on the PC knowledge gap, implicating GATA4 as a crucial principal regulator of PC biology. The goal of this proposal is to test the central hypothesis that GATA4 is required to maintain homeostasis of the mature gastric epithelium by directly controlling the gene expression program defining PC function. Studies in Aim 1 will define the mechanistic contribution of GATA4 to PC function using a conditional mouse model to delete GATA4 in PCs and a suite of morphological and molecular investigative tools. Studies in Aim 2, using a Gata4 conditional knock-in model uniquely available in our lab to overexpress GATA4 in PCs in conjunction with gastric injury, will provide evidence to determine the extent to which GATA4 loss is necessary for PC dysfunction and downstream metaplasia. We will also examine the contribution of GATA4 promoter hypermethylation to PC dysfunction and metaplasia. Finally, studies in Aim 3 will apply findings from the mouse to human PC biology using human gastric organoids to determine the extent to which GATA4 function in PCs is evolutionarily conserved. Overall, we expect our studies to elucidate GATA4-dependent molecular pathways essential to maintain PC function and health and that, when disrupted, cause PC dysfunction and gastric disease. Discoveries of fundamental cellular and molecular mechanisms, in this case those underpinning normal gastric epithelial cell homeostasis, can provide prerequisite knowledge to apply to future clinical applications for gastric diseases including gastritis, peptic ulcer disease, metaplasia, and cancer.