IGF2BP2 is Induced by Stress in the Heart and Mediates Dilated Cardiomyopathy

The IGF2BP family of RNA binding proteins consists of three paralogs that regulate intracellular RNA localization, RNA stability, and translational control. Although IGF2BP1 and 3 are oncofetal proteins, IGF2BP2 expression is maintained in many tissues, including the heart, into adulthood. Previous studies indicated that IGF2BP2 is upregulated in cardiomyocytes during cardiac stress and remodelling and returns to normal levels in recovering hearts. These results suggested that IGF2BP2 might play an adaptive role during cardiac stress and recovery. Using a conditional, inducible transgenic mouse line, we found that enhanced expression of the IGF2BP2 transgene in newborn or adult hearts leads to dilated cardiomyopathy (DCM), with remodelling, fibrosis, and death within 3-4 weeks. Downregulation of the transgene after 2 weeks, however, rescues these mice, with complete recovery by 12 weeks. Proteomic analysis identified a downregulation of sarcomeric and mitochondrial proteins in hearts overexpressing IGF2BP2, and electron microscopy revealed fragmented mitochondria and elongated, thinner sarcomeres. Consistent with these results, IGF2BP2 is upregulated in patients with DCM or after myocardial infarction. These results show that cardiac stress upregulates IGF2BP2, leading to remodelling and compensation of the heart. Prolonged expression, however, leads to heart failure and death, making it an attractive target for therapeutic intervention.