CL:1000409 'myocyte of sinoatrial node' vs CL:1000477 'cardiac pacemaker cell of sinoatrial node'

[GoogleCodeExporter]

id: CL:1000409
name: myocyte of sinoatrial node
is_a: CL:0002072  ! nodal myocyte

but there is another class:

CL:1000477 'cardiac pacemaker cell of sinoatrial node' 

in CL we have
CL:0002072 ! nodal myocyte [SYNONYM: "cardiac pacemaker cell" (exact)] 

if we define CL:1000477 in the obvious way it leads to an equivalence axiom

Original issue reported on code.google.com by cmung...@gmail.com on 20 Feb 2013 at 6:27

[gouttegd]

My understanding here is that the sinoatrial node contains both “cardiac pacemaker cells” and “transitional myocytes”, in which case the two terms myocyte of sinoatrial node (CL:1000409) and cardiac pacemaker cell of sinoatrial node (CL:1000477) are not actually redundant and should not be equivalent (since not all myocytes in the sinoatrial node are cardiac pacemaker cells).

I see two possible solutions here:

• either we say that nodal myocyte refers strictly to pacemakers cells (not to transitional cells that may also be found in the SA or AV nodes) – that's what the exact synonym “cardiac pacemaker cell” seems to imply –, in which case myocyte of sinoatrial node should not be a subclass of nodal myocyte (this one is defined as any muscle cell in the SA node) ;
• or nodal myocyte refers both to pacemakers cells and to transitional cells, in which case myocyte of sinoatrial node can indeed inherit from nodal myocyte – but then the exact synonym “cardiac pacemaker cell” on nodal myocyte should be relaxed.

[ghost]

My understanding here is that the sinoatrial node contains both “cardiac pacemaker cells” and “transitional myocytes”,

From https://www.ncbi.nlm.nih.gov/books/NBK459238/: "[SA node myocytes] have the ability to spontaneous (sic) generate an electrical impulse. It is the integrated activity of these so-called pacemaker cells that form the SA node. This electrical impulse is then transmitted by perinodal cells, or transitional (T) cells, to the right atrium... "

A "paranodal area" is also described in PMID:20946278: "Recent work has shown an extensive “paranodal area” in humans, located within the crista terminalis close to, but not continuous with, the SAN... The paranodal area comprises a mixture of loosely packed nodal and atrial myocytes and has a molecular architecture in some respects distinct and intermediate to the SAN and atrial muscle. Whereas in the SAN there is no Cx43 (connexin43—responsible for electrical coupling between cardiac myocytes) and no atrial natriuretic peptide (ANP), and in the atrial muscle there is both, in the paranodal area there is a heterogeneous mixture of myocytes, some of which express Cx43 and ANP while others do not..."

Perhaps the first point to clarify is whether CL:1000478 'transitional myocyte of the sinoatrial node' is actually part of the SAN or a separate, distinct "paranodal area".