SB201 Discussion Questions – Mechanical Patterning
Gut Folding Paper

The authors place their paper in context of the goal of unifying molecular and physical
descriptions of the complex process of gut morphogenesis, though their study focuses
exclusively on the physical forces involved in pattern formation of the looped gut. What
is known regarding molecular mechanisms underlying this process, and how might it be
integrated into their model? (e.g. what is responsible for different uniform growth rates
of the mesentery/gut?)

The physical model predicts the gut looping pattern based on the geometical and
biophysical properties of a species' gut and dorsal mesentery tissue--how are these
properties reproducibly established, and would a reliance on physical forces/properties
for such pattern formation be susceptible to issues of scaling?

The models in this paper are based on the elastic properties of tissues; in contrast, the
review paper (Grill 2011) states that "the notion of elasticity is not relevant for many of
the morphogenetic rearrangements that occur during development [since] these take
place on time-scales that are order of magnitude longer than those pertaining to
processes of relaxation of an elastically deformed tissue to an undeformed one"--is this
statement warranted?
SB201 Discussion Questions – Mechanical Patterning
Villification Paper

In what ways does the endoderm being so much stiffer than the mesenchyme affect
development? Is it necessary for it to buckle to form villi?

Are there other developmental processes where we would also see this stepwise
mechanical differentiation?

What might determine the necessary number of steps for these types of
differentiations? What would make us expect to see two or four step mechanical
processes in other structures?

Figure 1 is presented like it’s novel information, but it seems so basic. Had this really
not been studied before, and why? (when I looked, I just kept finding links to this same
paper)

Of the several animal models discussed, does human villi formation most closely
resemble mice (or is that known?)? Are villi more advantageous than the zigzags seen in
Xenopus/snakes?

Are there naturally occurring conditions in which villi formation is disrupted (i.e. muscle
diseases)? What are the effects (and do they tell us anything more about the
mechanism?)?

Does this mechanical forces mechanism apply to the patterning of other tissues?

Although SHH is showed to affect muscle formation, is there any genetic regulation involved in
vilification?

What is the mechanism for the uneven distribution of stem cell and uniform growth after zigzag
formation?