We performed a first comparative assessment of the levels of mRNAs encoding ion channels or gap junction proteins (Cacna1c, Kcnd2, Scn5a, Kcne1, Kcnv2, Gja5), ion channel regulators (Fxyd1), and proteins involved in ion channel localization and stabilization (Ank2, Cav3), structural and functional organization of intercalated disks (Cxadr), signal transduction (Akap9), gene transcription (Mef2c), and myosin function (Myl3) to study the expression of genes linked to AF development and discussed in the context of the hemizygous model (Seidl et al., 2017). The gene discussed is MYL3; the disease is atrial fibrillation.