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Overexpression of Cx43 and NF200 in Hibernating Species Citellus undulates During the Hibernation State

Document Type

Feature Article

Publication Date

Spring 5-1-2007

Publication Title

Washington University Undergraduate Research Digest: WUURD 2(2)

Abstract

Faculty Mentor: Igor R. Efimov

Most mammalian species experience cardiac arrhythmias in hypother- mic conditions. Hibernating mammals, on the other hand, are able to maintain proper cardiac conduction and rhythm even at -2o C body tem- perature. The purpose of this study was to understand the underlying molecular mechanisms utilized by the hibernating species Citellus undu- latus (Siberian ground squirrel, GS) that allow the GS to maintain prop- er conduction under extreme hypothermic conditions by looking at pro- tein expression in the left ventricular free wall. This study aims to quan- tify expression of connexin 43 (Cx43), the main ventricular gap junction- al protein, and neurofilament 200 (NF200), a marker of intracardial nerv- ous cells. Fluorescence immunohistochemistry was performed on trans- mural sections of the left ventricular free wall of summer active (SA, n=2), winter hibernating (WH, n=3), interbout arousal (IBA, n=3), and entrance into torpor (ET, n=2) ground squirrel (GS) heart. Quantitative analysis indicates that there is significant overexpression of Cx43 in WH epicardium and endocardium compared with ET and SA. NF200 expres- sion in the endocardium was found to be higher in WH GS than in ET, IBA, and SA. Citellus undulatus can maintain proper heart rhythm during extreme hypothermic conditions through overexpression of Cx43 in ven- tricular myocytes. For the first time, the pattern of autonomic innervation was characterized in endocardial ventricular tissue of a hibernating species through NF200 immunostaining. Overexpression of NF200 in WH indicates an important role of autonomic regulation in ventricular function during hibernation. Long-term goals of this research include contribution to treatments that allow for extended organ storage prior to transplantation, as well as development of anti-arrhythmia therapies.

From the Washington University Undergraduate Research Digest: WUURD, Volume 2, Issue 2, Spring 2007. Published by the Office of Undergraduate Research.

Henry Biggs, Director of Undergraduate Research and Associate Dean in the College of Arts & Sciences; Joy Zalis Kiefer, Undergraduate Research Coordinator, Editor, and Assistant Dean in the College of Arts & Sciences; Kristin Sobotka, Co-editor.

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