FGF12 Alleviates Cardiac Hypertrophy by Inhibiting Phosphorylation of CaM/CaMKII/CREB1 Axis

Hypertrophic cardiomyopathy (HCM) arises from genetic mutations in sarcomere proteins, resulting in major structural abnormalities and limited treatment options. Patients with HCM had reduced expression of the FGF12 (fibroblast growth factor 12), but its precise functional role remains unclear.

To explore FGF12's function and interactions, we utilized clustered regularly interspaced short palindromic repeats-Cas9 technology in cardiomyocytes derived from human induced pluripotent stem cells-induced cardiomyocytes, as well as in other cell lines and mouse models (MYH7^R403Q/+, MYBPC3^{c790GtoA/c790GtoA}, and transverse aortic constriction models). We transfected HCM or mice model with FGF12-coding sequence and FGF12-ΔNLS plasmids or adeno-associated virus 9 vectors to reduce myocardial hypertrophy. As hypertrophy progressed, we used cleavage under targets and tagmentation) sequencing and AlphaFold3 on myocardial tissues from patients and induced pluripotent stem cells-induced cardiomyocytes. To predict mitochondrial function in cardiomyocytes, we measured mitochondrial Ca²⁺ concentrations and reactive oxygen species content.

First, we observed a decrease in FGF12 expression and a difference in its subcellular localization in patients with HCM compared with healthy volunteers. In hypertrophic mouse models, injecting adeno-associated virus 9 reduced myocardial hypertrophy. FGF12 binds to calmodulin and inhibits its phosphorylation. This interaction also suppresses the expression and phosphorylation of downstream proteins, including CaMKII, ERK1/2, CREB1, and MCU. The nuclear-localization FGF12 binds to the promoter region of CREB1. FGF12 inhibits the expression of the CREB1-MCU axis expression, leading to reductions in both mitochondrial Ca²⁺ concentration and mitochondrial reactive oxygen species.

This study reveals a pathological mechanism associated with HCM linked to FGF12. FGF12, located outside the nucleus, suppresses the expression of metabolism-related genes by reducing the phosphorylation levels within the calmodulin-ERK1/2-CREB1-MCU axis. In contrast, the nuclear localization of FGF12 facilitates its binding to the promoter regions of CREB1, inhibiting CREB1 expression. This dual action maintains cardiomyocyte function and mitochondrial homeostasis. Our findings position FGF12 as a promising therapeutic target for HCM.