Developmental regulation of constitutive and inducible expression of hepatocyte-specific genes in the mouse.

Deletions in chromosome 7 of the mouse have been shown to cause failure of expression of certain liver-specific enzymes in newborn deletion homozygotes. Among these enzymes are L-tyrosine:2-oxoglutarate aminotransferase (EC 2.6.1.5) and phosphoenolpyruvate carboxykinase (GTP) [GTP:oxaloacetate carboxy-lase (transphosphorylating); EC 4.1.1.32]. The studies reported here show that in fetal stages constitutive expression of the relevant genes on the level of steady-state mRNA is identical in the livers of homozygous deletion mutants and normal littermates. Furthermore, prenatally these enzymes are expressed also in cell types other than hepatocytes. Thus, the putative trans-acting regulatory factors encoded in the deleted region of chromosome 7 of the mouse appear to be concerned specifically with the regulation of cell type-specific inducible expression of various hepatocyte-specific genes, whereas constitutive expression of the same genes is not affected.