Abstract 3197: miR-206 Mediates Yap-induced Cardiac Hypertrophy: A Component of the Mammalian Hippo Pathway Regulating Cardiac Hypertrophy
The Hippo pathway is an evolutionarily conserved signaling mechanism regulating organ size and cell death. Mammalian sterile 20 like kinase 1 (Mst1) and Lats2, tumor suppressor kinases, promote apoptosis and inhibit compensatory hypertrophy, thereby contributing to the development of heart failure. Lats2 phosphorylates and inhibits YAP, a transcription co-factor, which stimulates cardiac hypertrophy through interaction with transcription factors, including Tbx5 and TEF1. In Drosophila, Yorkie, a homologue of YAP, upregulates bantam, a microRNA, which in turn regulates growth and death. Thus far, a mammalian homologue of bantam has not been identified. In order to identify microRNAs involved in YAP-induced cardiac hypertrophy, total RNA was extracted from YAP-overexpressing neonatal cardiac myocytes (CM), enriched for small RNA, and analyzed by microarrays containing rodent microRNAs. Top upregulated microRNAs were selected, including miR-711, miR-483, miR-206 and miR-29c. Among them, miR-206 is a muscle specific microRNA, and its precursor is upregulated in skeletal muscle hypertrophy. We confirmed that YAP upregulates miR-206, using northern blot (+1.44 fold, p<0.05), qRT-PCR (+2.13 fold), and a 3′UTR luciferase reporter containing the targeting sequence specific for miR-206 (luciferase activity −51.0%). To examine the cardiac effects of miR-206, we made adenovirus vectors allowing us to either overexpress or knock down miR-206 in CM. Overexpression of miR-206 induced cardiac hypertrophy, as evidenced by increases in cell size (+1.17 fold), peri-nuclear atrial natriuretic factor (ANF) staining (+1.74 fold), ANF luciferase activity (+1.67 fold) and NF-AT luciferase activity (+1.95 fold). Downregulation of miR-206 attenuated YAP-induced cardiac hypertrophy, as evidenced by decreases in cell size (−15.0%), ANF luciferase activity (−64.4%), ANF western blot (−56.3%) and peri-nuclear ANF staining (−54.0%). These results suggest that miR-206 is necessary and sufficient for mediating YAP-induced cardiac hypertrophy in cardiac myocytes and, thus, functions as a mammalian homologue of Drosophila bantam.
This research has received full or partial funding support from the American Heart Association, National Center.