Identification of SOX2 Interacting Proteins in the Developing Mouse Lung With Potential Implications for Congenital Diaphragmatic Hernia

Abstract

Congenital diaphragmatic hernia is a structural birth defect of the diaphragm, with lung hypoplasia and persistent pulmonary hypertension. Aside from vascular defects, the lungs show a disturbed balance of differentiated airway epithelial cells. The Sry related HMG box protein SOX2 is an important transcription factor for proper differentiation of the lung epithelium. The transcriptional activity of SOX2 depends on interaction with other proteins and the identification of SOX2-associating factors may reveal important complexes involved in the disturbed differentiation in CDH. To identify SOX2-associating proteins, we purified SOX2 complexes from embryonic mouse lungs at 18.5 days of gestation. Mass spectrometry analysis of SOX2-associated proteins identified several potential candidates, among which were the Chromodomain Helicase DNA binding protein 4 (CHD4), Cut-Like Homeobox1 (CUX1), and the Forkhead box proteins FOXP2 and FOXP4. We analyzed the expression patterns of FOXP2, FOXP4, CHD4, and CUX1 in lung during development and showed co-localization with SOX2. Co-immunoprecipitations validated the interactions of these four transcription factors with SOX2, and large-scale chromatin immunoprecipitation (ChIP) data indicated that SOX2 and CHD4 bound to unique sites in the genome, but also co-occupied identical regions, suggesting that these complexes could be involved in co-regulation of genes involved in the respiratory system.

Expanding the genetics and phenotypes of ocular congenital cranial dysinnervation disorders

“…CUX1 is highly missense-constrained within humans (missense z=3.749). 16 Notably, CUX1 binds to known DRS-associated protein CHN1, 35 and a mutant CUX1 fly ortholog has abnormal neuroanatomy and neurophysiology (Supplementary Table 8). Largely LOF DNVs in CUX1 have been reported in global developmental delays with or without intellectual disabilities (MIM116896), a phenotype which was not documented in any of our three pedigrees.…”

SOX2 and SOX21 in Lung Epithelial Differentiation and Repair

“…So, SOX21 may fine-tune SOX2 function, and is important in maintaining a progenitor state, but it probably does not regulate sets of genes that are essential for the development of the esophagus, trachea or airways. It would be valuable to identify the genomic targets of SOX2 and SOX21, and recently it was shown that these factors have unique and common genomic binding sites, but it may also be interesting to evaluate binding profiles of these factors at varying levels of expression [ 30 ].…”

“…SOX proteins alone do not elicit their action, but require binding to other (mostly) transcription factors that provide specificity [ 26 , 31 , 32 ]. A number of putative SOX2 binding partners were identified in E18.5 lung using a mouse model containing a biotinylated SOX2 [ 30 , 33 ]. The contradicting phenotypes of increased or decreased differentiation in lung progenitors upon loss of SOX2 or SOX21, respectively, could be in part explained by differences in binding partners [ 14 , 18 ].…”