During development, cells shape epithelial tissues into distinct 3D structures with specialized molecular and mechanical regions. The vertebrate heart tube, for instance, extends by adding Second Heart Field (SHF) progenitor cells from the dorsal pericardial wall. Initially contributing to the entire cardiac primordium, SHF cell addition becomes restricted to the cardiac poles after the dorsal mesocardium breaks down. Disruptions in SHF deployment lead to congenital heart defects (CHD). The T-box genes Tbx1 and Tbx5, linked to CHD, regulate the development of arterial and venous poles as progenitor cells segregate.
This study presents quantitative morphometric analysis of SHF cells in the murine dorsal pericardial wall at embryonic days 8 and 9, using force inference image analysis to explore the relationship between cell shape and mechanical forces. We find that cell elongation and tension are key features of SHF morphology, with distinct differences in progenitor cells near arterial and venous poles. Analysis of Tbx1 and Tbx5 mutants reveals differential regulation of cell orientation and stress patterns. The project provide new insights into cardiac morphogenesis and CHD origins by integrating cell morphology, mechanical stress, and gene regulation.