Cardiac Characteristics of Transgenic Mice Overexpressing Refsum Disease Gene-Associated Protein within the Heart

Arrhythmia is a common cardiac symptom of Refsum disease. Recently, we identified a novel neuron-specific PAHX-associated protein (PAHX-AP1), which binds to the Refsum disease gene (PAHX). In this report, we developed heart-targeted transgenic (TG) mice under the control of alpha-myosin heavy chain promoter to determine whether cardiac overexpression of PAHX-AP1 provokes cardiac involvement symptoms. Northern and in situ hybridization analyses revealed PAHX-AP1 transcript was overexpressed in TG atrium, especially in the sinoatrial node. TG mice showed tachycardia, and tachyarrhythmia was observed in 20% of TG mice. Isolated TG atria showed higher frequency beating and were more sensitive to aconitine-induced tachyarrhythmia than the wild-type, and 40% of the TG atria showed irregular beating. Action potential duration in TG atrial fiber was shortened much more than the wild-type. Systemic administration of arrhythmogenic agents induced arrhythmia in TG mice, while no arrhythmia with the same dose in nonTG mice. Our results indicate that the chronic atrial tachycardia by overexpressed neuron-specific PAHX-AP1 transgene in atrium may be responsible for the increased susceptibility to arrhythmia.