An increased number of goblet cells (goblet cell hyperplasia, GCH) in the airway epithelium is largely responsible for the deleterious overproduction of mucin glycoproteins in response to allergens and environmental toxins in patients with asthma. The mechanisms that result in GCH have not been elucidated. This project focuses on identifying genes and pathways that direct the appearance of goblet cells (goblet cell metaplasia, GCM) in the interleukin (IL)13-induced murine model of allergic asthma, which is mediated by activation of the Stat6 signal transduction pathway. The overall hypotheses to be tested in this Exploratory/Developmental Research project is that the IMS-induced activation of Stat6 activates master genes, e.g. transcription factors with Stat6 cis-sequences, and that master gene products subsequently regulate switch genes that mediate goblet cell differentiation. We have recently performed temporal expression array profiling of murine trachea following exposure to IL13 or PBS and identified four candidate master genes upregulated early (1 h) following IL13 exposure and several candidate switch genes, which exhibit altered expression at an intermediate time (3.5 h) and return to base line levels at a later time (6 h).
In Aim 1, four candidate master genes will be evaluated to determine whether one or more are primary targets of Stat6. Candidate master genes will be evaluated for co-localization with IL4R and for binding to Stat6 by chromatin immunoprecipitation assay (ChIP) and functionally evaluated in vitro in murine tracheal epithelial (MTE) cells.
In Aim 2, candidate switch gene products will be evaluated for cellular and sub- cellular co-localization with master genes using confocal microscopy. Binding of master gene products to cis-elements in switch gene promoters will be evaluated. The ability of candidate switch genes to functionally induce GCM will be monitored following siRNA or transduction of switch genes into MTE cells. This study should define for the first time a pathway for goblet cell differentiation in a mammalian airway system. This will contribute to the development of pharmacological agents to control GCH and mucus overproduction in patients with asthma and possibly other chronic airway diseases ? ? ?
