An essential role in liver development for transcription factor XBP-1

XBP-1 is a CREB/ATF family transcription factor highly expressed in hepatoc ellular carcinomas. Here we report that XBP-1 is essential for liver growth . Mice lacking XBP-1 displayed hypoplastic fetal livers, whose reduced hema topoiesis resulted in death from anemia. Nevertheless, XBP-1-deficient hema topoietic progenitors had no cell-autonomous defect in differentiation. Rat her, hepatocyte development itself was severely impaired by two measures: d iminished growth rate and prominent apoptosis. Specific target genes of XBP -1 in the liver were identified as alpha FP,which may be a regulator of hep atocyte growth, and three acute phase protein family members. Therefore, XB P-1 is a transcription factor essential for hepatocyte growth.