Abstract 21011: Crispr/ndcas9 Adenoviral Vector System as a Tool for Promoting Mitochondrial Biogenesis in Cardiomyocytes

Abstract

Mitochondrial dysfunction contributes to heart failure. Our recent work revealed that genes in mitochondrial biogenesis and quality control, such as the peroxisome proliferator activated receptor gamma coactivator-1α(PGC-1α) and mitochondrial transcription factor A(TFAM), are downregulated in a rodent model of heart failure. Here, we apply CRISPR/Cas9 technology as a transcriptional activator to target sequences upstream of the start site to promote transcription of PGC-1α or TFAM. Since cardiomyocytes are difficult to transduce, we developed an adenoviral gene delivery system for expression of the CRISPR/Cas9 activating complex and a targeting gRNA to modulate expression of any gene of interest in differentiated cardiomyocytes, with our initial focus on activating the metabolic gene program. We use nuclease-dead Cas9 (ndCas9) fused to an activation domain VP64 and guide RNAs for activation of target genes. Proof-of-principle evidence was obtained by activating a cyclic AMP response element (CRE)-driven luciferase reporter gene and activation of endogenous CRE-regulable genes (PCK1 and PGC-1α). Next, we constructed ndCas9-gRNA adenoviral vectors to target PGC-1α and TFAM in the rat genome to determine if transcription of these genes can be increased. Functional effects of viral gene transduction in H9C2 cells and neonatal rat ventricular myocytes are assessed by determining mitochondrial DNA copy number (mtDNA)/genomic DNA ratio, and mtDNA quantity by picogreen labeling. Results: We have successfully upregulated the luciferase gene and endogenous CRE-regulated gene PCK1 in the same reporter cell line with ndCas9-VP64, as evidenced by significant increases in mRNA and protein expression levels. We have constructed and delivered adenoviral vectors with ndCas9 that are efficiently expressed by the host cells (NRVMs and H9c2 cells) and showed increased expression of PGC1a and TFAM in H9c2 cells. Importantly, an increase in mtDNA copy number was evoked by TFAM activation. For the first time, we show that the CRISPR/ndCas9 system can be used as a powerful tool for modulating transcription of native genes involved in mitochondrial biogenesis in cardiac cells, opening the door to developing novel therapeutic approaches for heart failure