TRANSGENIC MOUSE MODELS OF PANCREATIC EXOCRINE FUNCTION

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DESCRIPTION (provided by applicant): This grant application proposes to develop genetically engineered mouse models for acute pancreatitis and cystic fibrosis-related pancreatitis. We will focus on a recently discovered gene, which preliminary data suggest may play a role in development of pancreatitis, and also in the pathogenesis of cystic fibrosis (CF). The gene is called crpd in the mouse and dmbt1 in humans and it encodes the protein Muclin, a high molecular weight, and sulfated glycoprotein. This gene is most highly expressed in the exocrine pancreas, but also as different transcripts in other organs including the intestine, gallbladder, and kidney. The hypothesis is that Muclin is required for normal zymogen granule formation and subsequent solubilization of digestive enzymes upon exocytosis of the granules. We predict that if this gene is a disrupted zymogen granule will fail to mature creating a situation in the acinar cell where the zymogens will be prone to become activated, resulting in pancreatitis. The Muclin-deficient mouse model is intended to explore this hypothesis and, if this is borne out, it will make looking for mutations in this gene in human idiopathic pancreatitis a reasonable endeavor. We also predict that mice over expressing Muclin will exhibit poor release of zymogens after exocytosis and will be prone to CF-like plugging of the acinar lumen, which may predispose to pancreatitis. In CFTR-/- mice, a model for CF, the pancreas exhibits over expression of Muclin, which is associated with protein, plugs in the acinar lumen. Mice with a Muclin transgene targeted to the pancreas will allow testing of this hypothesis. The specific aims are to produce genetically engineered mice: 1). Globally deficient in Muclin by targeting the first exon, which is present in all transcripts of this gene. 2). An exocrine cell-specific defective Muclin by targeting the last exon which is translated only in exocrine cell transcripts of the gene and codes for a transmembrane domain that may be important for Muclin' s exocrine function; 3). That over expresses Muclin in the pancreatic acinar cell using the rat elastase promoter to direct cell specific expression.