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Author Spotlight: Effect of Left Atrial Ligation on Avian Embryonic Hearts and HLHS Implications
Published on: June 16, 2023
Left-Sided Heart Defects and Laterality Disturbance in Hypoplastic Left Heart Syndrome
1Department of Developmental Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15201, USA.
Insights
Hypoplastic left heart syndrome (HLHS) involves left-sided heart defects, potentially caused by laterality disturbance. This disturbance affects left-right patterning genes, impacting cardiovascular development and blood oxygenation.
Area of Science:
- Developmental Biology
- Genetics
- Cardiovascular Science
Background:
- Hypoplastic left heart syndrome (HLHS) is a severe congenital heart defect.
- The cause of left-sided heart hypoplasia in HLHS is not fully understood.
- Co-occurrence of HLHS with situs defects suggests a potential laterality disturbance.
Purpose of the Study:
- Investigate the role of laterality disturbance in HLHS.
- Explore the genetic basis of left-right patterning defects in HLHS.
- Understand the integration of heart development with asymmetric patterning.
Main Methods:
- Analysis of HLHS patient genetic variants in left-right patterning genes.
- Examination of HLHS mutant mouse models (Ohia mice).
- Investigation of gene regulation by Sap130 within the Sin3A chromatin complex.
Main Results:
- Pathogenic variants in left-right patterning genes are found in HLHS patients.
- Ohia mice with HLHS exhibit splenic defects, indicative of heterotaxy.
- Sap130 mutations in Ohia mice affect Lefty1 and Snai1, crucial for left-right patterning.
Conclusions:
- Laterality disturbance is implicated as a mediator of left-sided heart defects in HLHS.
- Shared mechanisms between HLHS and other congenital heart defects (CHD) may involve laterality.
- Integration of cardiac development with left-right patterning is vital for cardiovascular asymmetry and efficient oxygenation.
Abstract:
Hypoplastic left heart syndrome (HLHS) is a complex congenital heart disease characterized by hypoplasia of left-sided heart structures. The developmental basis for restriction of defects to the left side of the heart in HLHS remains unexplained. The observed clinical co-occurrence of rare organ situs defects such as biliary atresia, gut malrotation, or heterotaxy with HLHS would suggest possible laterality disturbance. Consistent with this, pathogenic variants in genes regulating left-right patterning have been observed in HLHS patients. Additionally, Ohia HLHS mutant mice show splenic defects, a phenotype associated with heterotaxy, and HLHS in Ohia mice arises in part from mutation in Sap130, a component of the Sin3A chromatin complex known to regulate Lefty1 and Snai1, genes essential for left-right patterning. Together, these findings point to laterality disturbance mediating the left-sided heart defects associated with HLHS. As laterality disturbance is also observed for other CHD, this suggests that heart development integration with left-right patterning may help to establish the left-right asymmetry of the cardiovascular system essential for efficient blood oxygenation.
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