Abstract 16976: A Mouse Model of Human Congenital Heart Disease: High Incidence of Diverse Cardiac Anomalies, Ventricular Noncompaction and Progressive Atrioventricular Block by Heterozygous Nkx2-5 Homeodomain Missense Mutation
Introduction: Heterozygous human NKX2-5 mutations are highly penetrant and associated with varied congenital heart defects (CHD) as well as progressive postnatal atrioventricular (AV) block, usually requiring pacemaker implantation. Heterozygous knockout of murine Nkx2-5, in contrast, manifests less profound CHD with low disease penetrance.
Hypothesis: We hypothesized that heterozygous knock-in having a disease-causing missense mutation rather than heterozygous knockout will mimic the phenotype of human patients.
Methods: Homeodomain (HD, DNA binding domain) missense mutations are the most frequently reported type of human NKX2-5 mutation, thus we replicated this genetic defect in a murine knock-in model (Arg52Gly) in a 129/Sv genetic background. Mouse phenotype was analyzed by histopathology (serial tissue sectioning, immunostaining), surface and telemetry ECG, and in vivo electrophysiology and compared to control Nkx2-5+/+ or Nkx2-5+/- mice at different postnatal stages from neonatal to 17 months of age.
Results: All heterozygous neonatal Nkx2-5+/R52G mice demonstrated a prominent trabecular layer in the ventricular wall, so-called noncompaction, along with diverse CHD, including ventricular septal defects (82%, n=17), atrioventricular septal defects (18%), and tricuspid valve anomalies (47%) such as Ebstein’s malformation. In addition, P10 Nkx2-5+/R52G mice demonstrated atrial septal anomalies, with significant increase in the size of the inter-atrial communication and fossa ovalis, and decrease in the length of the flap valve compared to control Nkx2-5+/+ or Nkx2-5+/- mice.
PR-prolongation (1st degree AV block) was present at 7 and 17 months of age but not at P1 and 4 weeks of age in Nkx2-5+/R52G versus control Nkx2-5+/+ mice. Advanced AV block was occasionally demonstrated in Nkx2-5+/R52G. In vivo electrophysiology studies showed that AV nodal function and right ventricular effective refractory period were impaired in Nkx2-5+/R52G mice, while sinus nodal function was not affected.
Conclusion: The effects of the human heterozygous missense mutations in NKX2-5 HD with highly penetrant, pleiotropic cardiac effects and progressive AV block was replicated in mice by introducing the missense mutation instead of knock-out.
Author Disclosures: M. Melanson: None. H. Ashraf: None. R. Chowdhury: None. M. Silberbach: None. H. Wakimoto: None. D. Benson: None. R. Anderson: None. H. Kasahara: Research Grant; Significant; NIH, AHA.
- © 2014 by American Heart Association, Inc.