The WT, Myh6-McmTam, and Mb21d1–/– mice had normal sinus rhythm and showed no cardiac arrhythmias except for occasional premature atrial contractions (Figure 9 and Supplemental Table 1; supplemental material available online with this article; https://doi.org/10.1172/jci.insight.192283DS1). The gene discussed is MYH6; the disease is chronic obstructive pulmonary disease.