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Margherita Battistara

In the fruit fly, Drosophila, mesoderm internalisation is very coordinated. Mesoderm cells constrict their apical surfaces, and the tissue folds inwards as a tube.

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Margherita Battistara

In the flour beetle, Tribolium, the tissue-scale outcome looks broadly similar. The mesoderm also internalises and forms a tube-like structure. But when you look closely, the cellular behaviours underlying this process are much less uniform.

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1 прямых ответов · 10 сообщений

Margherita Battistara

To compare the two systematically, we used morphospace analysis: a way to quantitatively map and compare 3D cell shapes during development. This method was previously applied to quantify cell shape noise ➡️ www.biorxiv.org/content/10.1...

Cell shape noise strength regulates the rate of shape change during EMT-associated cell spreadingCellular shape is intimately linked to cell function and state, and transitions between cell states are tightly coupled to shape changes. Yet, shape has been largely overlooked in state transitions st...www.biorxiv.org
Ответ для Margherita Battistara
Margherita Battistara

In Drosophila, cells follow a clear shape trajectory as the tissue folds. In Tribolium… not so much.

Ответ для Margherita Battistara
Margherita Battistara

Looking more closely, we found why: the beetle is not only folding its mesoderm. Some cells internalise early by dividing out of the epithelial plane, so that one daughter cell remains near the surface while the other is born directly inside the embryo.

Ответ для Margherita Battistara
Margherita Battistara

Why would cells do this? The clue was crowding. As the Tribolium mesoderm constricts apically, the tissue becomes increasingly packed.

Ответ для Margherita Battistara
Margherita Battistara

Using live imaging and interpretable machine learning, we found that small apical area and high nuclear crowding predict out-of-plane divisions.

Ответ для Margherita Battistara
Margherita Battistara

So the hypothesis is: The tissue is trying to fold as a tube. 🚇 Cells are also dividing. 👩‍👧‍👧 Space becomes limiting. 👥👥👥 And some cells appear to respond by dividing “downwards”, with one daughter cell leaving the epithelial layer and internalising early. ↔️↕️

Ответ для Margherita Battistara
Margherita Battistara

To test whether crowding was really driving out-of-plane divisions, we perturbed the two processes that could generate it: apical constriction and cell division. When apical constriction is abolished on the ventral side of the embryo, cells still divided — but all within the epithelial plane.

Ответ для Margherita Battistara
Margherita Battistara

We then did the complementary experiment: we blocked cell divisions by knocking down Tc-string. Here, cells still apically constricted, but they no longer divided. And the tissue folded much faster — around 50 minutes earlier.

Ответ для Margherita Battistara
Margherita Battistara

Together, these perturbations suggest that out-of-plane divisions arise when cell proliferation happens in an apically constricting tissue. They also show that proliferation and tissue folding can mechanically work against each other during gastrulation.

Ответ для Margherita Battistara
Margherita Battistara

In Drosophila, this conflict is normally avoided because mesodermal divisions are paused during gastrulation. Tribolium does not pause them — and out-of-plane divisions may be one way the tissue deals with the resulting crowding.