title: Novel chemical suppressors of long QT syndrome identified by an in vivo functional screen.
abstract: BACKGROUND
  Genetic long QT (LQT) syndrome is a life-threatening disorder caused by mutations that result in prolongation of cardiac repolarization. Recent work has demonstrated that a zebrafish model of LQT syndrome faithfully recapitulates several features of human disease, including prolongation of ventricular action potential duration, spontaneous early afterdepolarizations, and 2:1 atrioventricular block in early stages of development. Because of their transparency, small size, and absorption of small molecules from their environment, zebrafish are amenable to high-throughput chemical screens. We describe a small-molecule screen using the zebrafish KCNH2 mutant breakdance to identify compounds that can rescue the LQT type 2 phenotype.
  
  
  RESULTS
  Zebrafish breakdance embryos were exposed to test compounds at 48 hours of development and scored for rescue of 2:1 atrioventricular block at 72 hours in a 96-well format. Only compounds that suppressed the LQT phenotype in 3 of 3 fish were considered hits. Screen compounds were obtained from commercially available small-molecule libraries (Prestwick and Chembridge). Initial hits were confirmed with dose-response testing and time-course studies. Optical mapping with the voltage-sensitive dye di-4 ANEPPS was performed to measure compound effects on cardiac action potential durations. Screening of 1200 small molecules resulted in the identification of flurandrenolide and 2-methoxy-N-(4-methylphenyl) benzamide (2-MMB) as compounds that reproducibly suppressed the LQT phenotype. Optical mapping confirmed that treatment with each compound caused shortening of ventricular action potential durations. Structure activity studies and steroid receptor knockdown suggest that flurandrenolide functions via the glucocorticoid signaling pathway.
  
  
  CONCLUSIONS
  Using a zebrafish model of LQT type 2 syndrome in a high-throughput chemical screen, we have identified 2 compounds, flurandrenolide and the novel compound 2-MMB, as small molecules that rescue the zebrafish LQT type 2 syndrome by shortening the ventricular action potential duration. We provide evidence that flurandrenolide functions via the glucocorticoid receptor-mediated pathway. These 2 molecules and future discoveries from this screen should yield novel tools for the study of cardiac electrophysiology and may lead to novel therapeutics for human LQT patients.
authors.affiliation: Cardiovascular Research Center and Cardiac Arrhythmia Service, Massachusetts General Hospital, 149 13th St, Charlestown, MA 02129, USA.
authors.forename: David S
authors.initials: DS
authors.lastname: Peal
authors.forename: Robert W
authors.initials: RW
authors.lastname: Mills
authors.forename: Stacey N
authors.initials: SN
authors.lastname: Lynch
authors.forename: Janet M
authors.initials: JM
authors.lastname: Mosley
authors.forename: Evi
authors.initials: E
authors.lastname: Lim
authors.forename: Patrick T
authors.initials: PT
authors.lastname: Ellinor
authors.forename: Craig T
authors.initials: CT
authors.lastname: January
authors.forename: Randall T
authors.initials: RT
authors.lastname: Peterson
authors.forename: David J
authors.initials: DJ
authors.lastname: Milan
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D030801:Animals, Genetically Modified; D019556:COS Cells; D002522:Chlorocebus aethiops; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics; D005478:Flurandrenolone / Q000627:therapeutic use; D055785:Gene Knockdown Techniques / Q000379:methods; D057809:HEK293 Cells; D057166:High-Throughput Screening Assays / Q000379:methods; D006801:Humans; D008133:Long QT Syndrome / Q000235:genetics* / Q000503:physiopathology / Q000517:prevention & control*; D009154:Mutation / Q000235:genetics; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics*
chemical_list: D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D029961:Zebrafish Proteins; D005478:Flurandrenolone