Heterogeneous expression of mRNA in rat liver lobules as detected by differential display

Although liver hepatocytes appear to be uniform histologically, they are considerably heterogeneous with respect to their individual physiological capacities. In order to find still unknown genes that are heterogeneously expressed and with the aim of evaluating the usefulness of the differential display technique for this purpose, we performed differential displays with mRNA isolated from hepatocytes from the periportal and pericentral zone of the rat liver. In this way we identified at least two mRNAs exclusively expressed in the pericentral fraction. Sequence analysis revealed that the corresponding genes encode proteins with proline-glutamate dipeptide repeats similar to ones previously identified in rat pheochromocytoma and brain. In situ hybridization confirmed the heterogeneous distribution of the mRNA. Only one to two cell lines surrounding the terminal hepatic venules were positive, strongly resembling the heterogeneous expression of the enzyme glutamine synthetase. Our work demonstrates that the differential display method is a useful tool for the identification of genes that are differentially expressed in individual parenchymal cells. In fact, our results prove that differential display technology can be used for the identification of cellular markers for distinct subpopulations of cells in a given tissue.