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Updated: May 12, 2026
Isolation, Culture, and Functional Characterization of Adult Mouse Cardiomyoctyes
Published on: September 25, 2013
Progressive atrioventricular conduction defects and heart failure in mice expressing a mutant Csx/Nkx2.5 homeoprotein
H Kasahara1, H Wakimoto, M Liu
1Cardiovascular Division, Beth Israel Deaconess Medical Center, and Department of Medicine, Children's Hospital, Boston, Massachusetts, USA. hkasahar@caregroup.harvard.edu
Abstract:
A DNA nonbinding mutant of the NK2 class homeoprotein Nkx2.5 dominantly inhibits cardiogenesis in Xenopus embryos, causing a small heart to develop or blocking heart formation entirely. Recently, ten heterozygous CSX/NKX2.5 homeoprotein mutations were identified in patients with congenital atrioventricular (AV) conduction defects. All four missense mutations identified in the human homeodomain led to markedly reduced DNA binding. To examine the effect of a DNA binding-impaired mutant of mouse Csx/Nkx2.5 in the embryonic heart, we generated transgenic mice expressing one such allele, I183P, under the beta-myosin heavy chain promoter. Unexpectedly, transgenic mice were born apparently normal, but the accumulation of Csx/Nkx2.5(I183P) mutant protein in the embryo, neonate, and adult myocardium resulted in progressive and profound cardiac conduction defects and heart failure. P-R prolongation observed at 2 weeks of age rapidly progressed into complete AV block as early as 4 weeks of age. Expression of connexins 40 and 43 was dramatically decreased in the transgenic heart, which may contribute to the conduction defects in the transgenic mice. This transgenic mouse model may be useful in the study of the pathogenesis of cardiac dysfunction associated with CSX/NKX2.5 mutations in humans.
Insights
Mutant NKX2.5 protein impairs heart development, causing progressive conduction defects and heart failure in mice. This model aids research into congenital heart defects linked to NKX2.5 mutations.
Area of Science:
- Cardiovascular Biology
- Developmental Biology
- Genetics
Background:
- Mutations in the NKX2.5 gene are linked to congenital heart defects, specifically atrioventricular (AV) conduction abnormalities.
- The NKX2.5 homeoprotein is crucial for heart development, and its DNA-binding ability is essential for function.
Purpose of the Study:
- To investigate the in vivo effects of a DNA-binding impaired NKX2.5 mutant (I183P) on cardiac development and function.
- To establish a transgenic mouse model for studying the pathogenesis of cardiac dysfunction caused by CSX/NKX2.5 mutations.
Main Methods:
- Generation of transgenic mice expressing the I183P mutant allele of mouse Csx/Nkx2.5 under the control of the beta-myosin heavy chain promoter.
- Longitudinal assessment of cardiac function, including electrocardiography (ECG) to monitor P-R interval and AV block progression.
- Analysis of connexin 40 and 43 expression in the hearts of transgenic mice.
Main Results:
- Transgenic mice expressing Csx/Nkx2.5(I183P) exhibited progressive cardiac conduction defects and heart failure, despite appearing normal at birth.
- Significant P-R interval prolongation was observed, rapidly progressing to complete AV block by 4 weeks of age.
- Downregulation of connexins 40 and 43 was detected in the myocardium of affected hearts, correlating with conduction abnormalities.
Conclusions:
- A DNA-binding deficient NKX2.5 mutant causes severe, progressive cardiac conduction defects and heart failure in a mouse model.
- Reduced expression of connexins 40 and 43 likely contributes to the observed cardiac dysfunction.
- This transgenic model provides a valuable tool for understanding the mechanisms underlying human congenital heart diseases associated with NKX2.5 mutations.
