Embryonic VHL-HIF signaling defines dynamic heart metabolic compartments essential for cardiac maturation

While gene regulatory networks involved in cardiogenesis have been characterized, the role of bioenergetics remains less studied. Here we show that until midgestation, myocardial metabolism is compartmentalized, with a glycolytic signature restricted to compact myocardium contrasting with increased mitochondrial oxidative activity in the trabeculae. HIF1a regulation mirrors this pattern, with expression predominating in compact myocardium and scarce in trabeculae. By midgestation, the compact myocardium downregulates HIF1a and switches toward oxidative metabolism. Deletion of the E3 ubiquitin ligase Vhl results in HIF1a hyperactivation, disrupting metabolic compartmentalization and blocking the midgestational shift toward oxidative phosphorylation. Moreover, the altered glycolytic signature induced by HIF1 trabecular activation precludes regulation of genes essential for cardiac conduction system establishment. Our findings reveal VHL-HIF-mediated metabolic compartmentalization in the developing heart and the connection between metabolism and myocardial differentiation. These results highlight the importance of bioenergetics in ventricular myocardium specialization and its potential relevance to congenital heart disease. Overall design: RNA was isolated from individual E12.5 embryonic hearts after removal of the atria and valvular region. KOs and control littermates were matched by somite count, and a total number of 3 KOs and 3 controls from 3 independent litters were used. For RNA extraction, QIAzol Lysis Reagent (Qiagen; CA; USA) and the miRNeasy Mini Kit (Qiagen; CA; USA) were used. RNA was quantified and its purity checked with a NanoDrop ND-1000 spectophotometer (Thermo Scientific; MA; USA). RNA integrity was verified with an Agilent 2100 Bioanalyzer (Agilent Technologies; CA; USA). Index-tagged cDNA libraries were constructed from 500 ng of total RNA using the TruSeq RNA Sample Preparation v2 Kit (Illumina; CA; USA). Libraries were quantified by Quant-iTâ„¢ dsDNA HS assay in a Q-bit fluorometer (Life Technologies; CA; USA). Average library size and size distribution were determined by DNA 1000 assay in an Agilent 2100 Bioanalyzer. Libraries were normalized to 10nM using 10mM Tris-HCl, pH8.5 containing 0.1% Tween 20 and then applied to an Illumina flow cell for cluster generation (True Seq SR Cluster Kit V2 cBot) and sequencing-by-synthesis. Single reads of length 75bp were generated with the TruSeq SBS Kit v5 (Illumina; CA; USA) on the Genome Analyzer IIx platform, following the standard RNA sequencing protocol. Reads were further processed using the CASAVA package (Illumina; CA; USA) to split reads according to adapter indexes and produce fastq files.

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Menendez-Montes I, Escobar B, Palacios B, Gómez MJ, Izquierdo-Garcia JL, Flores L, Jiménez-Borreguero LJ, Aragones J, Ruiz-Cabello J, Torres M, Martin-Puig S