What happens if we alter tissue geometry? Our model predicted that in a linear heart, strain would be homogeneous, and fractures would run linearly. We put it to the test—making linear hearts in embryos—and voilà 😲 Homogeneous strain, mostly linear fractures, just like mechanical fractures 😎 9/n

are fractures and strain geometry dependent? Yes! As the heart grows, it twists & transforms from a simple tube into a two-chambered pump – maximum strain shifts accordingly, and ECM fractures follow suit—gradually concentrating in the outer curvature of the ventricle 8/n Geometry 🔛 Morphogenesis

but then why do these fractures happen only in the outer curvature? 🤔 It’s all about the unique geometry of ventricle! It's shape creates higher mechanical strain in the outer curvature, strong enough to locally fracture the cECM. Geometry 🔛 Morphogenesis! 7/n #zebrafish #DevBio #Morphogenesis

How do heart contractions fracture the ECM? @torres-sanchez.bsky.social & Daniel did some cool quantitative biophysical modelling and found that fracturing is mainly driven by how much myocardial tissue stretches! We blocked stretching (but not contraction speed) and saw fewer ECM fractures…6/n

What fractures ECM – synthesis/degradation? delaminating cells actively remodel ECM? upstream signalling? – nope! Chris developed a body-explant method to capture live ECM dynamics in beating hearts – found that ECM is initially smooth but gets fractured as the heart starts to beat forcefully 4/n

What about ECM? Can ECM restrict delamination locally? We found local thin ECM areas – fractures – restricted in the outer curvature, running across myocardial tissue, with signatures of mechanical defects. Cells delaminate into these fractures, and if we block fracturing, cells don’t delaminate 3/n

Stoked to present our latest, superbly led by Chris et al & @torres-sanchez.bsky.social We tackled a fundamental problem – how tissues are patterned during development – found that geometry-constrained ECM fractures pattern the myocardium in the vertebrate heart 1/n www.biorxiv.org/content/10.1...

More soon… but for now, feast your eyes on this HEADLESS zebrafish, still rocking a beating HEART— yellow (blood) magenta (endothelium) #Zebrafish #DevBio