Abstract 13324: Mouse Model of Human Congenital Heart Disease: High Incidence of Diverse Cardiac Anomalies and Ventricular Noncompaction by Heterozygous Nkx2-5 Homeodomain Missense Mutation
Background: The heterozygous knockout of murine Nkx2-5, in contrast, manifests less profound cardiac malformations, with low disease penetrance. We sought to study this apparent discrepancy in human and mouse genetics. Since missense mutations in the NKX2-5 homeodomain (DNA binding domain) are the most frequently reported type of human mutation, we replicated this genetic defect in a murine model.
Methods and Results: To address mechanistically whether a missense mutation in the homeodomain of NKX2-5 underlies a high disease penetrance, we generated a novel murine model in a 129/Sv genetic background by knocking-in a homeodomain missense mutation previously identified in humans. The mutation was located at homeodomain position 52Arg→Gly (R52G). To directly compare missense and nonsense mutations, we generated a second murine model, heterozygous Nkx2-5 knockout in a 129/Sv genetic background.
Periodically, newborn heterozygous Nkx2-5+/R52G mice were found cyanotic or dead. The ratio between P1 Nkx2-5+/+ (48%) vs. Nkx2-5+/R52G (52%) mice (n=65) and P10 Nkx2-5+/+ (58%) vs. Nkx2-5+/R52G (42%) mice (n=61) suggested that approximately one-quarter of the Nkx2-5+/R52G mice die perinatally. Detailed analyses using serial tissue-sectioning and 3-dimensional reconstruction of 15 P1 Nkx2-5+/R52G mice displayed complete penetrance of ventricular noncompaction, and a high incidence (~80%) of ventricular septal defects, as well as perinatal lethal complex cardiac anomalies, such as common atrioventricular junction, tricuspid atresia, or Ebstein’s malformation of the tricuspid valve. Furthermore, quantitative analyses from a total of 27 P10 hearts showed a significant increase in the size of the interatrial communication and the foramen ovalis, with the maximum length of the septum primum being decreased in Nkx2-5+/R52G compared to age-matched Nkx2-5+/+ or Nkx2-5+/- mice.
Conclusion: The results of our study demonstrate that heterozygous missense mutation in the murine Nkx2-5 homeodomain (R52G) are highly penetrant, and result in pleiotropic cardiac effects. Thus, in contrast to heterozygous Nkx2-5 knockout mice, the effects of the heterozygous knock-in mimic findings in humans with heterozygous missense mutation in NKX2-5 homeodomain.
- © 2013 by American Heart Association, Inc.