Abstract 637: A Pharmacogenetic Screen for Modifiers of Drug Induced QT Prolongation Reveals 15 Novel Genes.
Introduction: Variability in response to therapeutic drugs is a vexing problem that has recently begun to yield to intense investigatory efforts. Rigorous pharmacogenetic studies will require model systems that recapitulate the complexity of individual drug responses.
Methods: We have employed the voltage sensitive fluorescent dye di 4-ANEPPS and high speed CCD camera acquisition to study cardiac repolarization in embryonic zebrafish. We used a known zebrafish KCNH2 mutant, anemone toxin II (ATXII) and dofetilide to perturb cardiac repolarization. We also undertook a screen of a known panel of 294 mutant zebrafish lines to identify genes that modify the response to IKr block.
Results: Using optical mapping, we demonstrate action potential prolongation (Figure 1a,b⇓), reduced repolarization reserve (Figure 1d⇓), and spontaneous early afterdepolarizations in zebrafish harboring a mutation in KCNH2. We also show that augmentation of late sodium current using anemone toxin II prolongs action potential duration (Figure 1c⇓). Using this model we have conducted a pharmacogenetic screen for modifiers of drug-induced QT prolongation, and have identified 15 genes that modulate the response to IKr block, including three members of the heg-san-vtn pathway.
Conclusion: Together these data implicate a complex network of non-ion channel proteins functioning in membrane microdomains to regulate channel function, and validate high-throughput screening in zebrafish to dissect complex biologic systems.