R. Di Lisi et al., An atrioventricular canal domain defined by cardiac troponin I transgene expression in the embryonic myocardium, ANAT EMBRYO, 202(2), 2000, pp. 95-101
During early cardiac development the atrial myocardium is continuous with t
he ventricular myocardium throughout the atrioventricular canal. The atriov
entricular canal undergoes complex remodelling involving septation, formati
on of atrioventricular valves and insulation between atria and ventricles e
xcept at the level of the atrioventricular node. Understanding of these pro
cesses has been hampered by the lack of markers specific for this heart reg
ion. We have generated transgenic mice expressing beta-galactosidase under
the control of the cardiac troponin I gene that show transgene expression m
ainly confined to the atrioventricular canal myocardium during early embryo
nic development. With further development beta-galactosidase positive cells
are observed in the atrioventricular node and in the lower rim of both rig
ht and left atria, supporting the view that atrioventricular canal myocardi
um contributes to the atrioventricular node and is in part incorporated int
o the lower rim of the atria. These results identify the atrioventricular c
anal myocardium as a distinct transcriptional domain.