Background
Patch clamping studies using non-cardiomyocytes revealed that the human connexin40
mutations P88S, G38D, and A96S are associated with reduced gap junction conductances
compared to wild type connexin40 (wtCx40). Their effects within myocytes however are
unclear. We aimed to characterise P88S, G38D, and A96S after expression in rat hearts
and primary cardiomyocyte cultures.
Methods
Adult Sprague-Dawley rat atria were transduced with a lentivector containing a transgene
encoding wtCx40, P88S, G38D, A96S, or eGFP (n = 6 per transgene). Electrophysiology studies (EPS) were performed just prior to and
7 days after surgery. Left atria were assessed for connexin expression, mRNA levels,
inflammation and fibrosis. Primary cardiomyocyte cultures were also transduced with
the abovementioned vectors (n = 6 per transgene) and monolayer conduction velocities (CV) and protein expression were
assessed at 96 hours.
Results
At day 7 EPS, P wave and induced atrial fibrillation (AF) durations were significantly
longer in the mutant groups when compared to wtCx40 controls (p < 0.05). There were no significant differences in inflammation, fibrosis, or heart to
body weight ratios. Monolayer CV’s were reduced in the A96S group compared to the
wtCx40 group. While similar to wtCx40 controls, P88S velocities were reduced compared
to eGFP controls. G38D monolayers possessed spontaneous fibrillatory activity and
could not be paced. Immunofluorescence revealed that P88S and G38D reduced native
connexin43 myocyte coupling while A96S appeared to co-localise with connexin43 in
gap junctions. Connexin43 mRNA levels were similar between groups.
Conclusions
The A96S, G38D, and P88S Cx40 mutations slow conduction and increased the propensity
for inducible AF.
Keywords
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Article info
Publication history
Published online: March 21, 2017
Accepted:
February 6,
2017
Received in revised form:
December 20,
2016
Received:
July 11,
2016
Identification
Copyright
Crown Copyright © 2017 Published by Elsevier B.V. on behalf of Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). All rights reserved.
