Re: The sinoatrial node, connexin distribution patterns and specific immunodetection of connexin45

To the editor:In a recent paper in Cardiovascular Research, Verheijck et al. [1] examine the important topic of the electrophysiological properties of the sinoatrial (SA) node in relation to the distribution of different connexin types. It is certainly pleasing to see that these authors' results and conclusions on connexin distribution in the mouse SA node in many respects parallel our earlier published findings in the rabbit [2]. Unfortunately, however, these parallels are largely concealed to the reader by the authors' confused representation of our work. Muddling up citations (as, for example, in their statement referring to our report of connective tissue between the atrium and nodal tissue; Ref. [2], not Ref. [3] as cited) would alone be too trivial a matter to merit comment. However, the authors go on to state that Coppen et al. [2] reported the rabbit SA node to be connexin43 (Cx43) positive when, in fact—just as in the study of Verheijck et al. [1] in the mouse—we found the central SA node to be Cx43 negative. The confusion is then compounded by a series of comments that appear to cast doubt on the reliability and specificity of the Cx45 antibody used in our work demonstrating the SA node to be connexin45 positive [2]. Such comments undermine the research effort we have devoted to re-appraising and advancing investigation of the spatial and temporal expression patterns of Cx45 in cardiovascular and other tissues [2–11]. From this perspective, we feel it imperative that the record be set straight.The authors state that “Coppen et al. [3] showed that the Cx45 …