ETS1 and HLHS: Implications for the Role of the Endocardium

Area of Science:

• Genetics
• Developmental Biology
• Cardiology

Background:

• Congenital heart defects (CHDs) are a significant cause of infant mortality.
• Jacobsen syndrome, a chromosomal disorder, is associated with a high incidence of CHDs, including hypoplastic left heart syndrome (HLHS).
• The genetic underpinnings of HLHS and its association with Jacobsen syndrome remain incompletely understood.

Purpose of the Study:

• To identify the genetic cause of CHDs, specifically HLHS, in Jacobsen syndrome.
• To investigate the role of the ETS1 gene in heart development using model organisms.
• To elucidate the molecular mechanisms underlying HLHS pathogenesis and identify potential therapeutic targets.

Main Methods:

• Genetic analysis of patients with Jacobsen syndrome and CHDs.
• Gene expression studies in developing murine hearts.
• Functional studies of ETS1 in model organisms including *Ciona intestinalis*, *Drosophila*, and *Xenopus*.

Main Results:

• The ETS1 gene was identified as the causative gene for CHDs, including HLHS, in Jacobsen syndrome.
• ETS1 plays a critical role in cardiac neural crest and endocardial cell development.
• Studies in model organisms revealed ETS1's function in heart cell fate determination and migration, suggesting impairment of these processes leads to HLHS.
• A conserved "HLHS transcriptional network" involving ETS1 essential for early heart development was implicated.
• Evidence suggests HLHS left ventricular myocytes may be intrinsically normal in some patients.

Conclusions:

• ETS1 is a key gene in the pathogenesis of HLHS within Jacobsen syndrome.
• Dysregulation of ETS1 impacts cardiac cell fate and migration, leading to HLHS.
• The findings suggest a conserved genetic network critical for heart development and offer insights into potential therapeutic strategies for HLHS.