The mechanisms controlling tyrosine phosphorylation of cellular proteins are important in the regulation of many cellular processes, including development and differentiation. Protein tyrosine phosphatases (PTPases) may be as important as protein tyrosine kinases (PTKs) in these processes. PRL-1 is a distinct PTPase originally identified as an immediate-early gene in liver regeneration whose expression is associated with growth in some tissues but with differentiation in others. We now demonstrate that the PRL-1 protein is expressed during development in a number of digestive epithelial tissues. It is expressed at variable time points in the developing intestine, but its expression is limited to the developing villus enterocytes. In the gastric epithelium, PRL-1 expression in the adult is restricted to zymogen cells. PRL-1 is also expressed in the developing liver and esophagus and in the epithelia of the kidney and lung. In each of these contexts, the expression of PRL-1 is associated with terminal differentiation, suggesting that it may play a role in this important developmental process.

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