doi: 10.1161/01.RES.0000253088.77311.b1
© 2006 American Heart Association, Inc.
Editorials |
Tuning the Beat
Differential Expression of Ion Channels in the Sinus Node
From the Department of Medicine I, University Hospital Grosshadern, Ludwig-Maximilians-University, Munich, Germany.
Correspondence to Stefan Kääb, MD, Department of Medicine I, University Hospital Grosshadern, Ludwig-Maximilians-University, 81366 Munich, Germany. E-mail Stefan.Kaab@med.uni-muenchen.de
See related article, pages 1384–1393
Key Words: cardiac electrophysiology • sinoatrial node • pacemaker • transcription
An extract of the first 250 words of the full text is provided, because this article has no abstract. |
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Introduction |
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In this issue Tellez et al1 give a detailed analysis of differentially expressed genes regulating excitation and conduction in the sinoatrial node (SAN) in rabbit. Quantitative PCR and in situ hybridization, as well as action potential recordings, enabled the investigators to assign specific patterns to central and peripheral regions of SAN, and to compare these with the corresponding properteis of atrial tissue. Cluster analysis revealed that the SAN transcript profile is significantly different from that of atrial muscle. More importantly, there are apparent isoform switches on moving from atrial muscle to the SAN center: RYR2 to RYR3, Nav1.5 to Nav1.1, Cav1.2 to Cav1.3 and Kv1.4 to Kv4.2. In this context the transcript profile of the SAN periphery represents an intermediate pattern between that of central SAN and atrial muscle.
Differential expression of a variety of genes has been demonstrated in anatomically distinct regions of the heart, for example atrial versus ventricular myocardium,2 or ventricular endocardium versus ventricular epicardium,3 which gives clues to the molecular substrates controlling distinct myocardial electrical properties of specific regions in the heart.
Tellez et al meticulously dissected SAN tissue based on previous work and functional studies, and the authors were able to demonstrate that differential expression corresponds to specific electrical properties of SAN central, SAN periphery and free atrial myocardium. SAN central is characterized by poor electrical coupling to protect against inhibitory hyperpolarizing influence of surrounding atrial muscle. It provides ionic currents appropriate for pacemaking, resulting in spontaneous activity, a
Related Article:
Circ. Res. 2006 99: 1384-1393.