An initial hypothesis for the coiling of the gut proposed that similar inhomogeneous growth patterns within the mesentery or differential cell proliferation in the gut may have led to coiling.
However, an informal conversation at the origin of the collaboration with Tabin and co-author Natasza Kurpios inspired Mahadevan to propose a simpler hypothesis: that the gut grows uniformly faster relative to the mesentery.
Experiments showed that there are no non-uniformities in the cell proliferation patterns in the gut or the mesentery individually, and confirmed that the gut tube does, indeed, grow uniformly faster than the mesentery, to which it is attached.
As a result of this differential growth, the mesentery stretches, while the gut is compressed. When the elastic forces build up to a certain point, the gut tube buckles and coils.
The Harvard team also demonstrated that the web-like mesentery is integral to the shape of the developing gut. Kurpios and co-author Amy Shyer showed, through surgical manipulations, that removing the mesentery from an early-stage embryo in ovo prevented loops from forming, and removing it from a late-stage embryo caused the looping structure to relax.
These manipulations confirmed that while the gut tube and the mesentery lengthen at constant speeds, the difference in growth rate between the two attached tissues creates the opposing forces necessary for coiling.
To express this quantitatively, the researchers built a physical model of the process by sewing a silicone tube to the edge of a stretched sheet of latexwhich simulated the gutmesentery compositeand built mathematical and computational models of the coiling process.
|Contact: Caroline Perry|