Abstract 377: KLF15-TCF7L2-dependent Cardiac Transcriptional Reprogramming Induces Cardiomyocyte and Vascular Cell Remodeling in the Mammalian Heart

Integrative biochemical and omic-based approaches have refined our understanding of how cells integrate the Wnt signal at the chromatin level to yield specific cellular responses. However, this aspect remains unexplored in the heart. Since Wnt/β-catenin signaling activation is a hallmark in pathological cardiac remodeling, we aimed to characterize the specific Wnt cardiac transcriptional network regulation, amenable to therapeutic intervention in the adult heart.

In the adult heart, we found the transcription factor KLF15 occupying regulatory regions of tissue remodeling genes containing Wnt transcriptional activator, TCF7L2, binding sites, which are silenced in the healthy myocardium but are active during pathological remodeling. Supporting KLF15 repressive roles, its loss resulted in cardiac TCF7L2 activation, maladaptive reprograming and failure in vivo . We demonstrated that KLF15 possess transcriptional age-specific repressive functions controlling Wnt signaling, cardiomyocyte de-differentiation and vascular cell (VC) remodeling. Employing different transgenic mouse models we further identified a cooperative program inducing aberrant VC remodeling, caused by a reduction of KLF15 with a concomitant TCF7L2 activation in cardiomyocytes. Furthermore, we characterized a cardiac specific Wnt transcriptional inhibitory complex consisting of KLF15 directly interacting with β-catenin and TCF7L2 and identified the amino acids critical for these interactions. Next, using a CRISPR/Cas9-mediated approach we generated KLF15 knockout (KO) hESC lines differentiated into functional cardiomyocytes and used for engineering human myocardium (EHM) generation. KLF15 KO EHMs showed activation of TCF7L2-dependent transcription as well as impaired function in comparison to control lines, recapitulating the Klf15 KO mouse phenotype.

Altogether, we uncover an exquisite evolutionary conserved cardiac specific regulation mediated by KLF15 on Wnt signaling in myocardium offering a basis for designing highly specific pharmacological intervention for controlling Wnt cardiac-specific gene activation to prevent irreversible heart failure. We also underscore the significance of KLF15-Wnt dynamics in VC remodeling of the adult heart.