The keratin 19 promoter is potent for cell-specific targeting of genes in transgenic mice

(Background & Aims) under bar: Keratins are intermediate filaments that are critical in cytoskeletal organization. Their roles in cellular processes are underscored by inherited human diseases in which germline mutations of keratins are found, as well as by transgenic and knockout mouse models that recapitulate those diseases. Keratin 19 (K19) has unique structural properties and developmental and spatial expression patterns. This suggests that K19 expression may correlate with important cell fate decisions in gastrointestinal tract epithelia, (Methods) under bar: We used mouse K19 5' untranslated region and promoter sequences and fused it to the lacZ reporter gene in a transgene construct. Characterization was by beta -galactosidase expression and X-gal histochemistry in gastrointestinal epithelia, Because endogenous K19 protein is transcriptionally regulated by the Kruppel-like transcription factor 4 (KLF4), we determined the spatial expression patterns of KLF4 and K19 in relationship to the lacZ reporter gene product. (Results) under bar: K19-lacZ transgenic mice were found to have reporter gene expression in an epithelial-specific pattern. Expression was restricted to ductal epithelial cells in the pancreas, surface colonocytes, small intestinal villi, and gastric isthmus cells. Transgene expression correlated with K19 and KLF4 protein expression in the pancreas and stomach and was overlapping in the small and large intestine, (Conclusions) under bar: The K19 promoter may be a useful tool to study epithelial cell biology and subsequent transdifferentiation programs, particularly the pancreas and stomach.