Mechanical Feedback in Gut Looping

The midgut of most organisms consists of a long coiled tube that is dorsally attached to a thin sheet called the mesentery. Previous work has established that the physical foundations of the looping patterns arise from the differential growth between the gut tube and the mesentery in the context of their respective geometric and elastic properties, and that these looping patterns are evolutionarily modulated, at least in part, through species-specific variation in BMP2 levels, affecting the growth rates within the developing mesentey. However, how BMP2 signaling itself is modulated in an endogeneous setting remains unknown. We explore the possibility that tension in the mesentery feedbacks onto the tissue to regulate levels of BMP2, thereby controlling looping morphogenesis, using in-ovo and explant experiments. Quantifying this idea closes the feedback loop linking molecular signaling and gut morphogenesis in the chick embryo, and suggests an evolutionary pathway for exploring gut looping across organisms at a mechanistic level.