RYR2 and atrial fibrillation: Sixth, we have demonstrated that SOX4 can transactivate the expression of GJA1/Cx43 and SCN5A, alone or in synergy with TBX5, but the complex interaction between SOX4 and the other different players, such as LMNA, PITX2, RyR2, and others for the development of AF, remains to be elucidated.