PAH is a rare fatal disease characterised by increased muscularisation of pulmonary arteries leading to obliteration of the vessel lumens. To identify causal mutations in patients without a known genetic mutation, we undertook a whole-genome sequencing study of >1000 PAH patients and found that rare variants in SOX17 that are predicted to be deleterious to function were significantly associated with PAH.
SOX17 is a transcription factor that is highly expressed in endothelial cells and reported to be essential for endothelial function. The chief aim of this study is to explore the role of SOX17 in the pulmonary endothelium and how SOX17 deficiency may cause dysregulated vascular function. To achieve this, the two approaches are the knockdown of SOX17 using siRNAs and the generation of an iPSC line which harbours the SOX17R140Pmutation found in patients. Both tools will be used to evaluate the effect of altered SOX17 expression on endothelial integrity.
No significant difference was observed in the rates of apoptosis in SOX17-deficient cells while preliminary in vitro studies indicate these cells exhibit a decreased number of branch points during tube formation. Assessment of endothelial monolayer permeability and cell proliferation are in progress.
Furthermore, our GWAS project has identified a group of common variants in PAH patients ~100kb upstream of SOX17. Epigenetic data suggest these SNPs associate with a putative enhancer region. Selective cloning of this region into a zebrafish GFP reporter system showed 2/32 transgenic fish exhibiting vascular GFP expression, indicating SOX17 enhancer activity. A refined set of constructs are cloned to strengthen this observation and to determine whether the identified variants dysregulate SOX17 expression.
In summary, the data to date is providing this study with the multiple platforms that are necessary to address the role of variants within or near SOX17 in the mechanism underlying PAH pathology.