Cardiomyopathy in Irx4-deficient mice is preceded by abnormal ventricular gene expression

Area of Science:

• Cardiovascular Biology
• Developmental Biology
• Genetics

Background:

• The Iroquois family of homeobox transcription factors plays a role in mammalian development.
• The specific function of Irx4 in heart development and function remains to be fully elucidated.

Purpose of the Study:

• To investigate the role of the Irx4 gene in mammalian heart development and function.
• To determine the consequences of Irx4 gene disruption on cardiac morphology and gene expression.

Main Methods:

• Disruption of the murine Irx4 gene to create Irx4-deficient mice (Irx4(Delta ex2/Delta ex2)).
• Analysis of cardiac morphology and gene expression at various developmental stages (embryogenesis, neonatal, adult).
• Assessment of ventricular and atrial gene expression patterns, including Hand1, Irx2, atrial natriuretic factor, and alpha-skeletal actin.

Main Results:

• Irx4-deficient mice exhibited normal cardiac morphology during embryogenesis and early postnatal life.
• Adult Irx4(Delta ex2/Delta ex2) mice developed cardiomyopathy with cardiac hypertrophy and impaired contractile function.
• Irx4 deficiency led to abnormal ventricular gene expression, including reduced Hand1, increased Irx2, and altered chamber-specific gene expression, preceding cardiomyopathy.

Conclusions:

• Irx4 is essential for establishing a ventricle-specific gene expression program, though not for initial ventricular chamber formation.
• Loss of Irx4 function results in the deterioration of ventricular function and the development of cardiomyopathy.
• Other Irx genes (Irx1, Irx2, Irx5) may partially compensate for the absence of Irx4.