Discontinuous thoracic venous cardiomyocytes and heart exhibit synchronized developmental switch of troponin isoforms. (2nd January 2013)

• Record Type: Journal Article
• Authors: Kracklauer, Martin P.; Feng, Han‐Zhong; Jiang, Wenrui; Lin, Jenny L.‐C.; Lin, Jim J.‐C.; Jin, Jian‐Ping
• Is Part Of: FEBS journal. Volume 280:Number 3(2013)
• Page Start: 880
• Page End: 891
• Publication Date: 2013-01-02
• Subjects: cardiac muscle -- development -- myofilament protein -- pulmonary vein -- troponin isoform switch; Biochemistry -- Periodicals; Molecular biology -- Periodicals; Pathology, Molecular -- Periodicals; 572
• DOI: 10.1111/febs.12076
• Languages: English
• ISSNs: 1742-464X

Abstract

Abstract : Cardiomyocyte‐like cells have been reported in thoracic veins of rodents and other mammals, but their differentiation state and relationship to the muscle mass in the heart remain to be characterized. Here we investigated the distribution, ultrastructure, expression and developmental regulation of myofilament proteins of mouse and rat pulmonary and azygos venous cardiomyocytes. Tracing cardiomyocytes in transgenic mouse tissues using a lac Z reporter gene driven by a cloned rat cardiac troponin T promoter demonstrated scattered distribution of cardiomyocytes discontinuous from the atrial sleeves. The longitudinal axis of venous cardiomyocytes is perpendicular to that of the vessel. These cells contain typical sarcomere structures and intercalated discs as shown in electron microscopic images, and express cardiac isoforms of troponin T, troponin I and myosin. The expression of troponin I isoform genes and the alternative splicing of cardiac troponin T in thoracic venous cardiomyocytes are regulated during postnatal development in precise synchrony with that in the heart. However, the patterns of cardiac troponin T splicing in adult rat thoracic venous cardiomyocytes are slightly but clearly distinct from those in the atrial and ventricular muscles. The data indicate that mouse and rat thoracic venous cardiomyocytes residing in extra‐cardiac tissue possess a physiologically differentiated state and an intrinsically pre‐set developmental clock, which are apparently independent of the very different hemodynamic environments and functional features of the vessels and heart. Abstract : Abundant cardiomyocytes are present in mouse and rat pulmonary and azygos veins. These cells are disconnected from the heart muscle mass but exhibit mature sarcomeres, cardiac forms of contractile protein, and developmental regulations synchronized to that in the heart. Therefore the thoracic venous cardiomyocytes residing in extra‐cardiac tissue possess a physiologically differentiated state and an intrinsically preset developmental clock