A phenotype-based forward genetic screen identifiesDnajb6as a sick sinus syndrome gene

Sick sinus syndrome (SSS) is a group of heart rhythm disorders caused by malfunction of the sinus node, the heart’s primary pacemaker. Partially owing to its aging-associated phenotypic manifestation and low expressivity, molecular mechanisms of SSS remain difficult to decipher. Here, we aim to develop a phenotype-based forward genetic approach in the zebrafish (Danio rerio) animal model for discovering essential genes which dysfunction could result in SSS-like phenotypes. Previously we showed the generation of protein trap library by using a revertible gene-breaking transposon (GBT)-based insertional mutagenesis system. Here, we reported the generation of a collection of 35 zebrafish insertional cardiac lines derived from this protein trap library, which was screened using electrocardiographic measurements. As a result, three mutants with SSS-like phenotypes were identified. We then focused on one of these 3 GBT mutants calledGBT411in whichdnajb6bgene was disrupted, and conducted expressional, genetic, transcriptome, and electrophysiological studies using both zebrafish and mouse models. These studies confirmed the identity ofDnajb6as a novel SSS causative gene with a unique expression pattern within the specialized population of sinus node pacemaker cardiomyocytes that lack the expression of HCN4 channels. Together, this study demonstrates the feasibility of a genetic screening approach in an adult vertebrate animal model for discovering new genetic factors for a heart rhythm disorder such as SSS.