R-FunSel · In vivo functional screening via CRISPR-Cas9 to systematically identify cardiomyocyte receptors as targets for the innovative therapies for myocardial infarction and heart failure

Myocardial Infarction (MI) is the leading cause of heart failure, which represents a major medical, social and economic burden worldwide. There is a desperate need for new therapies for these conditions. Here we propose a new approach for the in vivo, unbiased and systematic identification of receptors involved in MI, which might become targets for innovative therapeutics. The method we developed, named Reverse Functional Selection (R-FunSel) takes advantage of the CRISPR/Cas9 genome editing technology and is based on the intracardiac screening of a library of single-guide (sg) RNAs in Cas9 transgenic mice upon gene delivery using the highly cardiotropic adeno-associated virus serotype 9 (AAV9). First, we will construct an arrayed library of sgRNAs, individually cloned into AAV9 vectors, driving CRISPR/Cas9 towards each of the receptor genes expressed by cardiomyocytes. Second, we will package pools of this library and transduce the mouse heart, at a multiplicity by which each vector enters a different cell. Then, MI will be applied as a selective stimulus and, after a few weeks, vector inserts will be recovered from the viable tissue and their frequency measured by Next Generation Sequencing. R-FunSel is based on Darwinian selection of cardiomyocyte survival, thus sgRNAs that will be lost are likely to target cardioprotective genes while those that are enriched code for detrimental factors. The choice to develop R-FunSel for the systematic screening of cardiomyocyte receptors will allow identification of novel druggable targets for the development of therapeutics, either in the form of molecules activating the protective receptors or inhibiting them or their ligands. R-FunSel is based on solid technologies that support the feasibility and power of the in vivo screening approach. Compared to biochemical or phenotypic studies, screening in vivo directly for function is a novel strategy to move basic research into translational medicine at a quick pace.