Abstract Body: Background
Following birth, cardiomyocytes (CMs) undergo a dynamic maturation process requiring coordinated mitochondrial expansion, translational and proteome remodeling to establish the mature oxidative phenotype. SLC25A1, a mitochondrial citrate carrier, is required for cardiac morphogenesis and mitochondrial metabolic reprogramming during embryonic development, but whether it coordinates postnatal CM maturation remains unknown.
Methods
CM-specific Slc25a1 knockout (Slc25a1-cKO) mice were generated using Slc25a1 floxed and Tnnt2-Cre lines. Gravimetric and survival analyses were performed across neonatal timepoints. Quantitative proteomic profiling by mass spectrometry was performed on Slc25a1-cKO and littermate floxed control hearts at postnatal day 28 (P28; n=5/genotype), with differentially abundant proteins assessed at q<0.1 and |FC|>1.5. Pathway enrichment was performed using Gene Set Enrichment Analysis (GSEA) against Gene Ontology and Reactome databases. Cardiac mitochondrial respiratory capacity was assessed by respirometry at P28.
Results
Slc25a1-cKO mice are born morphologically normal at P7 but exhibit systemic growth defects that emerge at P14 and become significant by P21. Reduced survival of mice relative to controls was also observed. At P28, when mitochondrial metabolic maturation is normally established in the mouse, Slc25a1-cKO hearts exhibited significantly decreased coupled and maximal uncoupled respiration. Quantitative proteomics identified 71 differentially abundant proteins, with a strong bias toward decreased abundance (68 downregulated vs. 16 upregulated in Cre vs. control). Downregulated proteins were notably enriched for mitochondrial oxidative phosphorylation machinery as well as mitochondrial translation, ribosome biogenesis, cytosolic translation. GSEA revealed significant negative enrichment of translation and electron transport chain programs across Gene Ontology: Biological Processes and Reactome databases. In contrast, upregulated proteins were enriched for lipid remodeling and stress-response pathways.
Conclusions
In conclusion, cardiomyocyte SLC25A1 is required for the neonatal cardiac maturation program and normal postnatal growth. Loss of Slc25a1 suppresses the coordinated translational and oxidative proteome networks necessary for cardiac maturation while activating stress-adaptive responses. These findings identify SLC25A1 as a previously unrecognized coordinator of neonatal cardiac maturation.