SMC5 Plays Independent Roles in Congenital Heart Disease and Neurodevelopmental Disability

Area of Science:

• Genetics
• Developmental Biology
• Cardiology

Background:

• Severe congenital heart disease (CHD) is linked to neurodevelopmental disability (NDD) in up to 50% of patients.
• Hypoxia during or after cardiac surgery is the presumed cause of NDD in CHD.
• Recent findings suggest a genetic overlap between CHD and NDD, but direct evidence linking CHD genes to NDD independent of hypoxia is limited.

Purpose of the Study:

• To investigate the role of the SMC5 gene in concurrent CHD and NDD.
• To determine if mutations in CHD-associated genes can cause NDD independently of hypoxic events.
• To model the impact of SMC5 mutations on cardiac and neurological development.

Main Methods:

• Case study of a patient with hypoplastic left heart syndrome and NDD with a de novo SMC5 mutation.
• Xenopus tropicalis embryo modeling of smc5 mutation to assess heart and brain development.
• Conditional knockout (cKO) of Smc5 in mouse cardiomyocytes to evaluate cardiac function.
• Conditional knockout (cKO) of Smc5 in the mouse central nervous system to assess brain structure and connectivity.

Main Results:

• Xenopus embryos with smc5 mutation showed reduced heart size, decreased brain length, and disrupted pax6 patterning.
• SMC5 cKO in mouse cardiomyocytes led to depleted mature cardiomyocytes and abnormal contractility.
• SMC5 cKO in the mouse brain resulted in reduced brain volume and impaired motor function connectivity, without affecting vascular or ventricular volumes.

Conclusions:

• Genetic factors, specifically mutations in genes like SMC5, can contribute to neurodevelopmental disability in patients with congenital heart disease.
• The findings challenge the sole reliance on hypoxia as the cause of NDD in CHD, highlighting a direct genetic link.
• SMC5 plays a crucial role in both cardiac and central nervous system development, suggesting a shared genetic etiology for concurrent CHD and NDD.