Using miRCURY LNA-miR-TSB in vivo to selectively block the mi-R31–5p/CALCR interaction, we tested causality between the miR-31–5p/CALCR interaction, atrial fibrosis, and AF development in the previously-validated Lkb1-aKD mouse model of spontaneous AF (fig. The gene discussed is STK11; the disease is atrial fibrillation.