Research Projects

Congenital heart defects (CHDs) represent the most common birth defects. While the etiology of more than 50% of CHDs remains unknown, human genetics studies have uncovered some of the genetic causes. Nevertheless, the disease mechanism downstream of the mutations remains difficult to decipher due to the paucity of suitable models. The structural defects in the CHDs result from disrupted morphogenesis caused by altered cell behaviours and cell-cell interactions among the multiple cell types that make up the heart. Therefore, a model that captures the cellular and structural complexity of the heart is key for disease research. We propose two objectives: 1) to generate murine stem-cell-based, self-organizing, 3D complex heart organoids, and 2) to test the utility of the generated organoids in modeling CHDs. We have discovered a critical step in the developmental trajectory of the heart. Recapitulating this step during pluripotent stem cell differentiation results in efficient cardiac organoid generation. Using this as a foundation, we propose to design a robust method for complex cardiac organoid generation from mouse embryonic stem cells. We will systematically enhance the organoid generation pipeline with a developmentally inspired approach to create cardiac organoids, which reflect the cellular and structural complexity of the mammalian heart. Using single-cell RNA-sequencing, we will analyze the cardiac cell types formed in the organoids. Subsequently, we will assess the structural complexity by marker gene expression analysis in situ. Then, we will drive the maturation of cardiomyocytes through metabolic rewiring and assess their contractile function by calcium imaging. Next, we will provide a proof-of-concept for the value of these organoids to model CHDs. We will generate cardiac organoids carrying a disease mutation in Gata4, encoding a cardiac transcription factor, to study ventricular septal defects. As an alternative strategy, in case septum formation is not reproducible in our model, we incorporate a single-cell transcriptomic approach to dissect the disease phenotype at the cellular and molecular level. This will provide a solid framework to address the developmental defects arising from the disease mutation. The outcome of the project will be a scalable, amenable model for research on CHDs. Moreover, it will be a stepping stone for developing the human heart organoid model, which can potentially revolutionize drug screening and research.