Although PLN is predominantly found in the ventricle (Bhupathy et al., 2007), we showed not only its expression is increased in the atria in the context of Tbx5 loss, but also PLN participates in rheostatic control of SERCA activity in the atria, which is sufficient to protect against AF inducibility (Figures 5–7). The gene discussed is TBX5; the disease is atrial fibrillation.