Dosage-sensitive RBFOX2 autoregulation promotes cardiomyocyte differentiation by maturing the transcriptome.

Area of Science:

• Molecular Biology
• Cardiovascular Research
• Developmental Biology

Background:

• Haploinsufficiency of RNA splicing regulator RBFOX2 is associated with congenital heart disease (CHD).
• The precise pathogenic mechanisms linking RBFOX2 to CHD remain largely unknown.
• RBFOX2 plays a critical role in regulating gene expression through alternative splicing.

Purpose of the Study:

• To elucidate the role of RBFOX2 in cardiomyocyte differentiation and its contribution to CHD pathogenesis.
• To investigate the autoregulatory splicing mechanism of RBFOX2 and its impact on isoform generation.
• To determine if ACTN2 overexpression can rescue RBFOX2 deficiency-related phenotypes.

Main Methods:

• Analysis of RBFOX2 function in cardiomyocyte differentiation.
• Investigation of splicing patterns in sarcomere, cytoskeletal, and focal adhesion genes.
• Assessment of autoregulatory splicing at mutually exclusive exons.
• Generation and analysis of heterozygous and null models.
• Functional rescue experiments involving ACTN2 overexpression.

Main Results:

• RBFOX2 is essential for cardiomyocyte differentiation, promoting mature splicing patterns.
• Disrupted autoregulation in heterozygous cells leads to skewed isoform ratios and dominant-negative products.
• Overexpression of alpha-actinin-2 (ACTN2) rescues heterozygous phenotypes by restoring contractility.
• A mechanosensing feedback loop involving RBFOX2 upregulation and transcriptome maturation is activated by ACTN2 rescue.

Conclusions:

• Decreased RBFOX2 dosage impairs cardiomyocyte differentiation by disrupting autoregulation and splicing.
• These disruptions contribute to CHD pathogenesis and heart failure susceptibility.
• RBFOX2 autoregulation is crucial for maintaining normal cardiac development and function.