Forkhead Box F1 as a mediator of Wnt signaling in human lung endothelial cells

Abstract

Pulmonary vascular diseases are associated with several congenital anomalies and often have limited treatment options because of their unknown pathogenesis, like Alveolar Capillary Dysplasia (ACD). Defective vascular development in ACD causes misaligned pulmonary veins, reduced number of capillaries and thickening of the alveolar septa, resulting in respiratory insufficiency and lethality in the newborn. ACD is associated with heterozygous mutations and large deletions that involve the <i>Forkhead Box F1 (FOXF1)</i> gene and its regulatory region, but the molecular mechanisms that cause these structural vascular abnormalities upon <i>FOXF1</i> gene alterations are not exactly known. Therefore, we aim to identify important FOXF1 molecular pathways and target genes in human endothelial cells in order to discover potential treatment targets. Human primary endothelial colony forming cells (ECFCS) have high FOXF1 expression and were isolated from human lungs. Immunoprecipitation of FOXF1 complexes followed by mass-spectrometry analysis identified β-catenin as an interaction partner of FOXF1, as well as two members of the β-catenin destruction complex, β-TrCP2 and CK1. Chromatin immunoprecipitation identified several FOXF1 binding sites in promoter regions containing a FOXF1 motif in close proximity to TCF/LEF1 binding sites. RNA-sequencing analysis upon <i>FOXF1</i> knock-down showed reduced expression of several β-catenin target genes, such as <i>BIRC5</i> and <i>CCNB1</i>. Collectively, these results suggest that FOXF1 is involved in Wnt signaling by interacting with β-catenin, thereby regulating the expression of β-catenin target genes in human lung endothelial cells.