Functional Characterization of Evolutionarily Conserved DNA Regions in Forkhead Box F1 Gene Locus.

The Forkhead Box f1 (Foxf1) transcription factor (previously known as HFH-8 or Freac-1) is expressed in the septum transversum and splanchnic (visceral) mesoderm and is required for proper development of gut-derived organs. Sequence comparisons of mouse and human Foxf1 genes have revealed highly conserved DNA sequences located within the -5.3-kb Foxf1 promoter region and the 400-nucleotide regulatory element located 1 kb 3' to the Foxf1 gene (3'RE). To examine their transcriptional activity during mouse embryonic development, we generated transgenic mice in which the expression of the beta-galactosidase transgene was controlled by the -2.7-kb Foxf1 promoter region, the -5.3-kb Foxf1 promoter region, or the -5.3-kb Foxf1 promoter region fused to the 3'RE. The -5.3-kb Foxf1 promoter sequences induced appropriate transgene expression in the midgut and developing intestine, whereas the -2.7-kb Foxf1 promoter region was transcriptionally inactive. Addition of 3'RE to the -5.3-kb Foxf1 promoter restored proper transgene expression in the foregut, liver, and lung mesenchyme and prevented ectopic transgene expression in the developing nervous system. Cotransfection studies demonstrated that FoxA2 protein bound to the 3'RE region (+4506/+4529 bp) and was sufficient to inhibit expression of the -5.3-kb Foxf1 promoter. Furthermore, C/EBPbeta and HNF-6 proteins bound to the 3'RE region (+4647/+4694 bp) and provided synergistic transcriptional activation of the -5.3-kb Foxf1 promoter in cotransfection assays. These studies demonstrated that the conserved Foxf1 3'RE region is essential for proper tissue-specific regulation of the Foxf1 promoter region during mouse embryogenesis.