Non-targeted metabolomics of Brg1/Brm double-mutant cardiomyocytes reveals a novel role for SWI/SNF complexes in metabolic homeostasis
Mammalian SWI/SNF chromatin-remodeling complexes utilize either BRG1 or Brm as alternative catalytic subunits to alter the position of nucleosomes and regulate gene expression. Genetic studies have demonstrated that SWI/SNF complexes are required during cardiac development and also protect against cardiovascular disease and cancer. However, Brm constitutive null mutants do not exhibit a cardiomyocyte phenotype and inducible Brg1 conditional mutations in cardiomyocyte do not demonstrate differences until stressed with transverse aortic constriction, where they exhibit a reduction in cardiac hypertrophy. We recently demonstrated the overlapping functions of Brm and Brg1 in vascular endothelial cells and sought here to test if this overlapping function occurred in cardiomyocytes. Brg1/Brm double mutants died within 21 days of severe cardiac dysfunction associated with glycogen accumulation and mitochondrial defects based on histological and ultrastructural analyses. To determine the underlying defects, we performed nontargeted metabolomics analysis of cardiac tissue by GC/MS from a line of Brg1/Brm double-mutant mice, which lack both Brg1 and Brm in cardiomyocytes in an inducible manner, and two groups of controls. Metabolites contributing most significantly to the differences between Brg1/Brm double-mutant and control-group hearts were then determined using the variable importance in projection analysis. Increased cardiac linoleic acid and oleic acid suggest alterations in fatty acid utilization or intake are perturbed in Brg1/Brm double mutants. Conversely, decreased glucose-6-phosphate, fructose-6-phosphate, and myoinositol suggest that glycolysis and glycogen formation are impaired. These novel metabolomics findings provide insight into SWI/SNF-regulated metabolic pathways and will guide mechanistic studies evaluating the role of SWI/SNF complexes in homeostasis and cardiovascular disease prevention.
KeywordsSWI/SNF complex BRG1 BRM Cardiomyocyte Metabolomics Fatty acid Glucose
- Ang II
BRG1- or BRM-associated factors
Brahma-related gene 1
LoxP-flanked DNA polymerase gene
Cre recombinase fused to a mutated ligand-binding domain of human estrogen receptor
Retinoid X receptor alpha
Peroxisome proliferator activated receptor
PPAR-gamma coactivator 1-alpha
Vascular endothelial cells
Variable importance in projection
The authors would like to thank Kumar Pandya for providing the αMHC-Cre-ERT transgenic mice and advice on adding tamoxifen to the rodent chow. The authors would like to acknowledge Janice Weaver (University of North Carolina Animal Histopathology Laboratory) and Victoria Madden (University of North Carolina Microscopy Services Laboratory) for assistance in preparing histological specimens and performing the TEM, respectively. Finally, the authors would also like to thank Tim Koves for his guidance and valuable discussion and suggestions for harvesting and preparing heart samples for metabolomics analysis. This work was supported by the National Institutes of Health (R01HL104129 to M.W. and RO1 CA125237 to S.J.B.), a Jefferson-Pilot Corporation Fellowship (to M.W.), and the Fondation Leducq (to M.W.).
Conflict of interest
The authors declare that they have no conflict of interest.
Compliance with Ethical Standards
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.
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