Kcnh2 Expression Profile and Continuous EEG/ECG Monitoring in a Rabbit Model of Long QT Syndrome Type 2

Abstract

Long QT Syndrome (LQTS) is a classically studied cardiac condition characterized by a prolonged ventricular excitation-repolarization interval (QT interval) on an electrocardiogram (ECG). LQTS is associated with an increased risk of arrhythmias and sudden cardiac death. People with LQTS, particularly those with Long QT Syndrome Type 2 (LQT2), are also at an increased risk of seizures/epilepsy. LQT2 is caused by loss of function variants in the KCNH2 gene. The dual neuro-cardiac phenotype of LQT2 can likely be explained by expression of KCNH2 in both the brain and heart. Using a rabbit model that harbors an endogenous knock-in mutation in one allele of the pore domain of the Kcnh2 gene, I characterized the molecular expression of WT vs. mutant Kcnh2 and developed a protocol for long-term subcutaneous EEG/ECG implantation.

To better understand the molecular profile of WT vs. mutant rabbits, the relative expression of WT vs mutant Kcnh2 transcripts was evaluated using quantitative PCR (qPCR) with verification via Oxford Nanopore Technology (ONT) sequencing. Additionally, 44 RNA sequencing libraries were prepared and sequenced for further analysis of the molecular profile of WT vs mutant rabbits. Micro-C and high molecular weight DNA libraries were also prepared for the construction of a more thorough rabbit genome.

In mutant rabbits, total Kcnh2 expression is roughly half that of WT rabbits. In mutant rabbits, the mutant Kcnh2 RNA represents 11% of the total Kcnh2. These data suggest that most mutant Kcnh2 RNA is degraded shortly after generation.

To continuously monitor the rabbits’ cardiac and neuronal electrical function in vivo, a method of constant EEG/ECG recording was designed and implemented. It involves the surgical placement of subdermal electrodes and the design and manufacturing of a wiring system. The surgical placement of electrodes has been optimized to minimize time and number of incisions and improve outcomes. The wiring system enables the rabbits to have free range of motion within the housing cage and keeps all wires protected and out of reach of the rabbits. This system is functional and generates high quality continuous EEG/ECG recordings.