Synchronous down-modulation of miR-17 family members is an early causative event in the retinal angiogenic switch

Six members of the microRNA-17 (miR-17) family were mapped to three different chromosomes, although they share the same seed sequence and are predicted to target common genes, among which are those encoding hypoxia-inducible factor-1α (HIF1A) and VEGFA. Here, we evaluated the in vivo expression profile of the miR-17 family in the murine retinopathy of prematurity (ROP) model, whereby Vegfa expression is highly enhanced at the early stage of retinal neovascularization, and we found simultaneous reduction of all miR-17 family members at this stage. Using gene reporter assays, we observed binding of these miRs to specific sites in the 3′ UTRs of Hif1a and Vegfa . Furthermore, overexpression of these miRs decreased HIF1A and VEGFA expression in vitro. Our data indicate that this miR-17 family elicits a regulatory synergistic down-regulation of Hif1a and Vegfa expression in this biological model. We propose the existence of a coordinated regulatory network, in which diverse miRs are synchronously regulated to target the Hif1a transcription factor, which in turn, potentiates and reinforces the regulatory effects of the miRs on Vegfa to trigger and sustain a significant physiological response. Significance Retinal angiogenesis is a finely tuned biological phenomenon and a major cause of blindness. We studied the regulation of this phenomenon and identified cross-talk involving microRNAs (miRs) that share the same seed sequence, transcription factors, and angiogenesis effectors. In a mouse model of retinopathy of prematurity, we show the down-regulation of all miR-17 family members as an early event in the angiogenic switch, which resulted in increased levels of hypoxia-inducible factor-1α and Vegfa in vitro. Notably, this coordinated regulation did not require the marked quantitative alterations of an individual miR but instead, relied on synchronous changes in members that share the same seed sequence. These results identify potential therapeutic targets in eye diseases with abnormal retinal angiogenesis.