HEPATOCYTE-SPECIFIC EXPRESSION OF THE MOUSE HEPATOCYTE GROWTH-FACTOR LIKE PROTEIN

We have cloned and characterized the gene and complementary DNA for a new kringle-containing protein. Although the function of this protein is not known, it has been called hepatocyte growth factor-like protein because it shares the same structural domains as hepatocyte growth fa ctor, with four kringle structures followed by a region homologous to serine proteases. To determine if hepatocyte growth factor-like protei n is synthesized by the same cells as hepatocyte growth factor, we sur veyed adult mouse and developing mouse embryo tissues by in situ hybri dization analysis using radiolabeled RNA for hepatocyte growth factor- like protein. Results of in situ hybridization analysis of adult mouse tissues show that among all surveyed tissues specific signal was rest ricted to the liver. Higher magnification of liver sections shows that hepatocytes were the only cell type expressing messenger RNA for hepa tocyte growth factor-like protein, contrary to the reported presence o f hepatocyte growth factor messenger RNA in fat-storing cells. A simil ar liver-restricted and hepatocyte-specific pattern of messenger RNA e xpression was observed in the developing mouse embryo at 14 days of ge station. All other developing tissues that were analyzed, as well as l iver hematopoietic cells, did not express messenger RNA for hepatocyte growth factor-like protein at levels detectable by this technique. We conclude that although structurally similar to hepatocyte growth fact or, hepatocyte growth factor-like protein is a novel protein synthesiz ed primarily in hepatocytes.