Identification and characterization of a transcribed distal enhancer involved in cardiac Kcnh2 regulation

The human ether-a-go-go-related gene KCNH2 encodes the voltage-gated potassium channel underlying IKr, a current critical for the repolarization phase of the cardiac action potential. Mutations in KCNH2 that cause a reduction of the repolarizing current can result in cardiac arrhythmias associated with long QT syndrome. Here, we investigated the regulation of this critical cardiac gene and identified multiple active enhancers in the Kcnh2 locus. An enhancer ~85 kbp downstream of Kcnh2 physically contacted the promoters of two Kcnh2 isoforms in a cardiac-specific manner in vivo. Knockdown of a ncRNA controlled by this enhancer results in reduced expression of Kcnh2b and two neighboring mRNAs, Nos3 and Abcb8, in vitro. Genomic deletion of the enhancer, including the ncRNA transcription start site, from the mouse genome caused a modest downregulation of both Kcn2a and Kcn2b in the ventricles. These findings establish that the regulation of Kcnh2a and Kcnh2b is governed by a complex regulatory landscape that involves multiple partially redundantly acting enhancers. Overall design: 4C-seq on adult murine hearts and livers to identify contact profiles of the Kcnh2 promoter and or cis-regulatory element Kcnh2_CRE11