Arteriovenous Shunt in an Epas1^A529V Mutant Mouse

The recently described EPAS1 gain-of-function mutation syndrome (Pacak-Zhuang syndrome) is characterized by a constellation of multiple paragangliomas and pheochromocytomas, duodenal somatostatinoma, and polycythemia caused by postzygotic gain-of-function mutations in the EPAS1 gene, encoding for hypoxia-inducible factor 2α (HIF-2α). Because development of ocular structures requires proper coordination of hypoxia signaling, researchers evaluated patients with the syndrome for eye abnormalities and developed and evaluated a transgenic mouse model with a somatic heterozygous Epas1^A529V mutation (corresponding to the human EPAS1^A530V mutation) to establish the role of HIF-2α in the development of eye pathologies identified in the patients. This video of time-lapse fluorescein angiography demonstrates a venous plexus out towards the periphery of the eye with plexiform arteriovenous shunting (arrow) in a mutant mouse, mimicking some of the findings seen in humans. This and other findings from the mouse model suggests that HIF-2α is a critical component of the development of choroid and retinal vasculature and that abnormal vascular patterns in patients are developmental in origin. Click the related article for full details and discussion.