To analyze whether the synthesis of ECM proteins by the OAF cells is altered due to Tnmd deficiency, we next performed immunofluorescence analysis for Col I, which is the main protein component of OAF; Fn, which plays a pivotal role in facilitating AF cell attachment and fiber alignment (Attia, Santerre, & Kandel, 2011); and Lum, which interacts with collagen fibrils and contributes to AF mechanical properties (Sztrolovics, Alini, Mort, & Roughley, 1999). Here, TNMD is linked to atrial fibrillation.