Abstract 222: The Estrogen-related Receptor (ERR) Drives Cardiac Myocyte Maturation in Cooperation With GATA4

Abstract

During transition from fetal to adult developmental stages, the heart undergoes robust mitochondrial biogenesis in parallel with growth and structural maturation. Recently we identified a role for ERRα/γ in this broad program of postnatal cardiac maturation. We sought to delineate the mechanisms whereby ERRs coordinate transcriptional regulation of both metabolic and structural genes in the maturation of human induced pluripotent stem cell-derived cardiac myocytes (hiPSC-CMs). CRISPR-based gene deletion studies demonstrated that ERRα/γ is necessary for activation of genes involved in mitochondrial and structural maturation during hiPSC-CM differentiation including mitochondrial function, ion transport, Ca 2+ handling, and the adult sarcomere. Whole-genome RNA-sequencing and ChIP-sequencing (ChIP-seq) studies indicated that ERRγ directly regulates both metabolic and structural genes by remodeling H3K27ac depositions in related enhancer regions. Integration of the ERRγ ChIP-seq data with published hiPSC-CM datasets demonstrated that approximately 50% of super-enhancer regions overlapped ERRγ peaks, suggesting ERR is involved in the maintenance and function of cardiac super-enhancer regions. Corresponding motif analyses and intersection analyses with published GATA4 ChIP-seq datasets suggested that ERRγ cooperates with GATA4 on many structural, but not metabolic targets. Specifically, binding sites for both factors are often co-localized around cardiac contractile, ion channel, and Ca 2+ handling genes, including TNNI3, MYBPC3, MYH7, TTN, KCNQ1, and RYR2 . In contrast, ERRγ sites on target genes involved in mitochondrial maturation such as ATP5B, COX4I1, CPT1B , and FABP3 lacked GATA4 sites. Experiments using luciferase reporters demonstrated functional cooperation between ERRγ and GATA4 that depends on the known ERR coactivator, peroxisome proliferator-activated receptor gamma co-activator 1alpha (PGC-1α). We conclude that the ERR cooperates with GATA4 to drive cardiac structural gene transcription during cardiac differentiation, whereas ERR regulates genes involved in energy metabolism independent of GATA4. Activation of ERR signaling could prove to be an effective tool to drive hiPSC-CM maturation.