INVOLVEMENT OF ISK-ASSOCIATED K-RATE CONTROL OF REPOLARIZATION IN A MURINE ENGINEERED MODEL OF JERVELL-AND-LANGE-NIELSEN-SYNDROME( CHANNEL IN HEART)

The Jervell and Lange-Nielsen (JLN) syndrome affects the human cardioa uditory system, associating a profound bilateral deafness with an abno rmally long QT interval on the EGG. It results from mutations in KVLQT 1 and ISK genes that encode the 2 subunits forming the K+ channel resp onsible for the cardiac and inner ear slowly activating component of t he delayed rectifier K+ current (I-Ks), A JLN mouse model that present s typical inner ear defects has been created by knocking out the isk g ene (isk-/-), This study specifically reports on the cardiac phenotype counterpart, determined in the whole animal and at mRNAs and cellular levels. Surface ECG recordings of isk-/- mice showed a longer QT inte rval at slow heart rates, a paradoxical shorter QT interval at fast he art rates, and an overall exacerbated QT-heart rate adaptation compare d with wild-type (WT) mice, A 300-ms increase in the heart rate cycle length induces a 309+/-21% increase in the QT duration of the WT mice versus a 500+/-50% in isk-/- mice (P<0.001), It is concluded that the isk gene product and/or I-Ks, when present, blunts the QT adaptation t o heart rate variations and that steeper QT-RR relationships reflect a greater susceptibility to arrhythmias in patients lacking I-Ks.