Deletion of the minK gene in mice resulted in absent IKs and reduced IKr currents, but no changes in ECGs, with minK expression restricted to the cardiac conduction system.
Does minK gene deficiency alter cardiac delayed rectifier currents and ECG characteristics in mice?
The minK gene modulates IKs and IKr currents in mice, and its expression is highly restricted to the cardiac conduction system, suggesting species-specific roles in cardiac electrophysiology.
The minK gene encodes a 129-amino acid peptide the expression of which modulates function of cardiac delayed rectifier currents (IKr and IKs), and mutations in minK are now recognized as one cause of the congenital long-QT syndrome. We have generated minK-deficient mice in which the bacterial lacZ gene has been substituted for the minK coding region such that beta-galactosidase expression is controlled by endogenous minK regulatory elements. In cardiac myocytes isolated from wild-type neonatal mice, IKs is rarely recorded, while IKr is common. In minK (-/-) myocytes, IKs is absent and IKr is significantly reduced and its deactivation slowed; these results further support a role for minK in modulating both IKs and IKr. Despite these changes, ECGs in (+/+) and (-/-) animals are no different at adult and at neonatal stages. ECG responses to isoproterenol are also similar in the 2 groups. beta-Galactosidase staining in postnatal minK (-/-) hearts is highly restricted, to the sinus-node region, caudal atrial septum, and proximal conducting system. Moreover, as early as embryonal day 11, segmentally restricted beta-galactosidase expression is observed in the portions of the sinoatrial and atrioventricular junctions that are thought to give rise to the conducting system, thereby implicating minK expression as an early event in conduction system development. More generally, the restricted nature of minK expression in the mouse heart suggests species-specific roles of this gene product in mediating the electrophysiological properties of the heart.
Kupershmidt et al. (Fri,) conducted a other in minK gene expression / cardiac conduction system. minK gene deletion (minK -/-) vs. Wild-type mice (+/+) was evaluated on IKs and IKr currents, ECG parameters, and beta-galactosidase expression. Deletion of the minK gene in mice resulted in absent IKs and reduced IKr currents, but no changes in ECGs, with minK expression restricted to the cardiac conduction system.