• Shashank Gandhi

Using cardiac neural crest to rescue congenital heart defects

Updated: Jun 19, 2021

How do you fix a broken heart?

The neural crest is an embryonic stem cell population that gives rise to several critical cell types in the adult animal. Different subpopulations of the neural crest follow distinct migratory paths during development and consequently contribute to distinct cell types. One of these subpopulations is known as the cardiac neural crest, which migrates into the developing heart and separates the blood vessels that deliver deoxygenated blood to the lungs and oxygenated blood to the rest of the body. The cardiac neural crest's ability to contribute to heart development is unique, as replacing these cells in a chicken embryo even with closely related stem cell tissues leads to a heart defect similar to one found in humans.

I probed the molecular mechanisms that allow cardiac neural crest cells to septate the outflow tract in avian embryos (Gandhi et al., Developmental Cell, 2020). I found laterality differences in cardiovascular defects resulting from unilateral cardiac neural fold ablations between the left and right sides, with left ablation causing a higher proportion of Double Outlet Left Ventricle (DORV) compared to a right ablation, which caused a higher proportion of Persistent Truncus Arteriosus (PTA). We then resolved the heterogeneity within the migratory cardiac neural crest using single-cell RNA sequencing and reported an earlier-than-expected onset of gene expression that is associated with cardiac neural crest's ability to form heart muscle. Using CRISPR-Cas9-mediated loss-of-function analyses, I established the regulatory relationships between cardiac neural crest genes Sox8, Tgif1, and Ets1, and found that Tgif1 functioned in a cardiac neural crest subcircuit important for specification and proper septation of the outflow tract. Ectopic expression of this cardiac crest subcircuit, comprising of Sox8, Tgif1, and Ets1, was sufficient to reprogram trunk neural crest cells towards a cardiac neural crest-like fate, enabling them to migrate to the heart and rescue the effects of a cardiac crest ablation. These results have helped elucidate the genetic properties of the cardiac neural crest lineage in the formation and proper functioning of the heart, helping uncover potential target genes involved in cardiovascular birth defects.

Image: Cardiac neural crest cells migrate into the heart to septate the outflow tract into the aortic (Ao) and pulmonary (PT) trunks. Knocking out Tgif1 results in cardiovascular defects similar to the ones caused when trunk neural crest is grafted in place of the cardiac neural crest. However, genetically reprogrammed trunk neural crest cells can rescue the defects caused by cardiac neural crest ablation.

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