Disruption of the HNF-4 gene, expressed in visceral endoderm, leads to cell death in embryonic ectoderm and impaired gastrulation of mouse embryos.

Abstract

Expression of HNF-4, a transcription factor in the steroid hormone receptor superfamily, is detected only in the visceral endoderm of mouse embryos during gastrulation and is expressed in certain embryonic tissues from 8.5 days of gestation. To examine the role of HNF-4 during embryonic development, we disrupted the gene in embryonic stem cells and found that the homozygous loss of functional HNF-4 protein was an embryonic lethal. Cell death was evident in the embryonic ectoderm at 6.5 days when these cells normally initiate gastrulation. As assessed by expression of Bracbyury and HNF-3P, primitive streak formation and initial differentiation of mesoderm do occur, but with a delay of ~24 hr. Development of embryonic structures is severely impaired. These results demonstrate that the expression of HNF-4 in the visceral endoderm is essential for embryonic ectoderm survival and normal gastrulation.

The origin and efficient derivation of embryonic stem cells in the mouse

“…Very close proximity is established between early postimplantation epiblast and primitive endoderm in vivo through discontinuities in their shared basal lamina (21), which could provide a basis for their interaction. Furthermore, there is compelling evidence that the visceral endoderm is essential for normal growth and differentiation of the epiblast in the intact conceptus (22). That complete dissociation had no discernible effect on the efficiency with which epiblast gave rise to ES lines argues against a requirement for homotypic cell interactions in their production.…”

Efficiency of embryoid body formation and hematopoietic development from embryonic stem cells in different culture systems

“…ES cells become blood cells through a series of developmental steps. ES cells on the outer surface of the developing EBs di erentiate into primitive endoderm that regulates cell fate decisions of remaining pluripotent cells, including the process of gastrulation whereby cells of the three embryonic germ layers are formed (Chen et al, 1994). Mesoderm derived hemangioblasts are thought to give rise to both hematopoietic and endothelial cells (Choi et al, 1998;Faloon et al, 2000;Yamashita et al, 2000).…”

Embryonic development of the liver

“…133,134,139 Hnf4 knockout embryos die before the onset of liver development due to a crucial role for this factor in regulating extra-embryonic endoderm function. 140,141 However, HNF4␣ was also found to be essential for hepatocyte differentiation when the extraembryonic endoderm deficiency was circumvented either by generating mice from Hnf4 Ϫ/Ϫ embryonic stem cells using tetraploid embryo complementation or by ablation of Hnf4 specifically in hepatoblasts using the Cre/loxP system. 133,134,142 Analyses of livers from E18.5 Hnf4 loxP/loxP AlfpCre embryos revealed that hepatic morphology, including the distribution of sinusoids, was severely perturbed and hepatocytes lacking HNF4␣ failed to express a plethora of genes associated with hepatocyte activity.…”