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Author: Satara A. Brown, Medical University of
South Carolina, Class of 2014
Introduction: Purkinje cardiomyocytes are
specialized cardiomyoctes that connect to working cardiomyocytes to
facilitate contraction of the heart muscle. Connexin 40 (Cx40) is
the predominant connexin found in gap junctions of Purkinje
cardiomyocytes; however, Cx43 and Cx45 are predominant in working
cardiomyocytes. In working cardiomyocytes following myocardial
infarction (MI), Cx43 remodeling occurs, which is indicated by
lateralization of Cx43 and ensuing arrhythmias. We hypothesize that
in murine Purkinje cardiomyocytes, MI will cause disorganization of
Cx40 expression at gap junctions.
Methods: A Cx40EGFP/+ transgenic mouse model
post-surgical ligation of the left anterior descending artery was
utilized to conduct this study. EGFP, enhanced green fluorescence
protein, allowed identification of Purkinje cardiomyocytes.
Antibodies to detect pan-cadherin and Cx40 were used in
immunofluorescence staining of tissues. Immunofluorescence and
confocal microscopy were employed to image gap junctions and
intercalated disks in EGFP areas. Differences in Cx40 expression,
cadherin expression, and colocalization of Cx40 and cadherin in
control mice and mice that have experienced MI were quantified.
Results: Cx40 remodeling was indicated by
decreased Cx40 expression, decreased cadherin expression, and
decreased colocalization of Cx40 and cadherin in the Purkinje cell
areas. Cx40 expression decreased by 56%, cadherin expression
decreased by 69%, and colocalization decreased by 24%. This
indicated that gap junctions were deficient and relocated from
their normal locations at intercalated disks following MI.
Conclusion: These results parallel changes that
have been detected with Cx43 expression in working cardiomyocytes.
Alterations in Cx40 in Purkinje cells may be responsible for
life-threatening arrhythmias that can occur post-MI. These findings
in the mouse model can be used to develop a treatment for post-MI
arrhythmias in humans in the future
October 2012 Issue of IMpact