Choreographed morphogenetic events underlie early foregut development in the mouse embryo

During embryonic days 7.5 to 8.5, the mouse embryo experiences a significant reshaping of its anterior region, a phenomenon known as ventral folding. This complex process involves the simultaneous development of the cardiac crescent, cranial headfolds, and the anterior foregut, which collectively establish the body's antero-ventral plan.

Although the mechanisms behind cardiac morphogenesis have been extensively studied, the cellular and mechanical underpinnings of foregut involution have remained largely unclear. To address this knowledge gap, researchers employed a combination of light-sheet and spinning-disk live imaging techniques to monitor foregut formation throughout its entire development window.

Their findings reveal that involution unfolds through a highly structured morphological program that does not rely on actomyosin contractility for its onset. Prior to this involution, a wave of apoptosis emerges in a spatially and temporally limited manner, targeting embryonic visceral endoderm (emVE) cells and causing them to extrude bidirectionally.

By analyzing emVE, definitive endoderm, and epiblast populations using lineage- and stage-resolved bulk RNA-sequencing, researchers identified a distinct differential-adhesion and cell-cycle signature associated with this behavior. Further investigation into a visceral-endoderm-specific Bmp2 knockout mutant uncovered that BMP2 indirectly controls involution by influencing notochord positioning and, in turn, the mechanical dynamics of the heart and headfold structures.

In summary, these discoveries suggest that ventral folding is not a series of unconnected events, but rather a unified geometric process that orchestrates the development of the mouse embryo's anterior structures.