FLVCR2 Regulation of Intracellular Heme Modulates Vascular Tip/Stalk Specification During Retinal Angiogenesis

Area of Science:

• * Molecular biology
• * Developmental biology
• * Cell biology

Background:

• * Fowler syndrome is an embryonic lethal disease linked to FLVCR2 mutations, causing CNS vascular defects.
• * FLVCR2 mutations are associated with hypovascularization and glomeruloid formations.
• * Previous studies showed reduced brain vascularization in Flvcr2 gene deletion models.

Purpose of the Study:

• * To elucidate the mechanisms of FLVCR2 regulation in retinal angiogenesis.
• * To investigate the role of FLVCR2 in retinal vascular development.
• * To explore how FLVCR2 influences angiogenic signaling pathways.

Main Methods:

• * Conditional knockout of Flvcr2 in mice.
• * Knockdown of Flvcr2 in primary bovine retinal endothelial cells.
• * Chemical inhibition of heme synthesis and supplementation with heme precursors.

Main Results:

• * Deletion of Flvcr2 reduced vascular expansion and caused abnormal glomeruloid formation.
• * Flvcr2 knockdown decreased cellular heme, promoted NOTCH signaling, and increased proliferation.
• * Heme supplementation or using cell-permeable hemin reversed these effects.
• * FLVCR2/heme signaling attenuates NOTCH1 activation and prevents VEGF-induced proliferation.

Conclusions:

• * FLVCR2 plays a critical role in regulating retinal angiogenesis.
• * Heme acts as a key mediator in FLVCR2's function.
• * FLVCR2 and heme signaling are essential for tip/stalk cell specification in angiogenesis.