Molecular architecture of the human specialised atrioventricular conduction axis.
The atrioventricular conduction axis, located in the septal component of the atrioventricular junctions, is arguably the most complex structure in the heart. It fulfils a multitude of functions, including the introduction of a delay between atrial and ventricular systole and backup pacemaking. Like any other multifunctional tissue, complexity is a key feature of this specialised tissue in the heart, and this complexity is both anatomical and electrophysiological, with the two being inextricably linked. We used quantitative PCR, histology and immunohistochemistry to analyse the axis from six human subjects. mRNAs for ~50 ion and gap junction channels, Ca(2+)-handling proteins and markers were measured in the atrial muscle (AM), a transitional area (TA), inferior nodal extension (INE), compact node (CN), penetrating bundle (PB) and ventricular muscle (VM). When compared to the AM, we found a lower expression of Na(v)1.5, K(ir)2.1, Cx43 and ANP mRNAs in the CN for example, but a higher expression of HCN1, HCN4, Ca(v)1.3, Ca(v)3.1, K(ir)3.4, Cx40 and Tbx3 mRNAs. Expression of some related proteins was in agreement with the expression of the corresponding mRNAs. There is a complex and heterogeneous pattern of expression of ion and gap junction channels and Ca(2+)-handling proteins in the human atrioventricular conduction axis that explains the function of this crucial pathway.
Cardiovascular Medicine, Faculty of Medical and Human Sciences, University of Manchester, UK.
I D
ID
Greener
O
O
Monfredi
S
S
Inada
N J
NJ
Chandler
J O
JO
Tellez
A
A
Atkinson
M-A
MA
Taube
R
R
Billeter
R H
RH
Anderson
I R
IR
Efimov
P
P
Molenaar
D C
DC
Sigg
V
V
Sharma
M R
MR
Boyett
H
H
Dobrzynski
D001145:Arrhythmias, Cardiac / Q000378:metabolism; D001283:Atrioventricular Node / Q000166:cytology* / Q000378:metabolism*; D020747:Calcium Channels, T-Type / Q000378:metabolism; D051244:Caveolin 3 / Q000378:metabolism; D018031:Connexin 43 / Q000378:metabolism; D017630:Connexins / Q000378:metabolism; D004594:Electrophysiology; D017629:Gap Junctions / Q000378:metabolism; D006329:Heart Conduction System / Q000166:cytology* / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007473:Ion Channels / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D062554:NAV1.5 Voltage-Gated Sodium Channel; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015222:Sodium Channels / Q000378:metabolism
C121855:CACNA1G protein, human; D020747:Calcium Channels, T-Type; D051244:Caveolin 3; D018031:Connexin 43; D017630:Connexins; C468137:GJD3 protein, human; D007473:Ion Channels; D009124:Muscle Proteins; D062554:NAV1.5 Voltage-Gated Sodium Channel; C568320:SCN5A protein, human; D015222:Sodium Channels