The four-chambered mammalian heart develops from two fields of cardiac progenitor cells (CPCs) distinguished by their spatiotemporal patterns of differentiation and contributions to the mature heart. The first heart field (FHF) differentiates earlier in lateral plate mesoderm, generates the linear heart tube, and ultimately gives rise to the left ventricle. The second heart field (SHF) differentiates later in pharyngeal mesoderm, elongates the heart tube, and gives rise to much of the right ventricle and outflow tract (OFT). We have demonstrated that the zebrafish heart develops in a similar way to the mammalian heart - from both FHF and SHF progenitors - despite the zebrafish heart being comprised of a single ventricular chamber.
Current Projects in the Burns Lab include:
Cardiovascular Progenitor Cell Biology: We have identified multiple lineages that differentiate from nkx2.5+ progenitor cells in the lateral plate mesoderm. We have also found that SHF ventricular progenitors follow an independent trajectory compared to progenitors that give rise to the OFT and pharyngeal arch arteries (PAAs) during zebrafish development. We are currently addressing the cellular and molecular heterogeneity of nkx2.5+ progenitors in the lateral plate mesoderm and pursuing genetic mechanisms that regulate development of each subpopulation.
Congenital Heart Disease modeling: We have taken variants identified in humans with specific CHDs and created loss-of-function mutations in the orthologous zebrafish gene(s) in order to directly implicate the variants in disease pathogenesis and to uncover its mechanism of action. We are currently pursuing an Rbfox-deficient model of hypoplastic left heart syndrome (HLHS) and an NAA15-deficient model of CHD. In addition to zebrafish, we have also created and are characterizing human iPSC-derived cardiomyocytes devoid of RBFOX2. We are also continuing to pursue the role of Tbx1 in driving 22q11 deletion syndrome/DiGeorge Syndrome using a zebrafish model.
CRISPR screening: We are generating gRNA libraries to knock-out genes in zebrafish that are orthologous to human variants linked to left-sided lesions such as HLHS, bicuspid aortic valve, and aortic arch hypoplasia. W are also generating libraries to knock-out genes that are highly expressed in nkx2.5+ progenitors in the ALPM. We will perform a rolling screen where hits are prioritized based on CHD association, novelty, and gene function.