The Evidence Layer for Scientific AI

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Evidence supporting the mechanism

In stage-10A Drosophila follicular epithelium, activating the TGF-β/BMP receptor pathway with constitutively active Tkv increased the shg/E-cadherin transcriptional reporter by 5.25-fold (n=10, P=4×10⁻⁵) and increased E-cadherin at bicellular junctions by 1.85-fold (n=12, P=0.0002). At tricellular junctions, the reported TCJ:BCJ E-cadherin signal ratio was 5.22:1 (n=12, P=3.1×10⁻¹⁰), consistent with preferential E-cadherin enrichment or retention at vertices. Direct Drosophila follicular-epithelium study

What “independent of actomyosin” means

The result does not mean actin and Myosin II are irrelevant to all E-cadherin biology. It means that the specific TGF-β-dependent prevention of tricellular-junction opening remained when Myosin II activity was reduced: E-cadherin still accumulated at vertices by 2.85-fold (n=11, P=2.84×10⁻⁶). TGF-β can also elevate Myosin II through Rho–Rok, but that contractile branch was dispensable for this barrier-protective outcome. Thus, signaling appears to strengthen junctional adhesion through increased E-cadherin availability and spatial retention, rather than requiring contractile tension to create the effect. Myosin-II perturbation result

Interpretive boundary

“E-cadherin clustering” is a useful shorthand for the observed vertex enrichment, but the supplied records do not report super-resolution measurements proving nanocluster formation, direct molecular oligomerization, altered cadherin binding kinetics, or a complete endocytic mechanism. p120-catenin increased approximately twofold, yet was not essential, implying that redundant downstream effectors may stabilize E-cadherin. The conclusion is therefore strongest as: TGF-β signaling promotes E-cadherin accumulation and retention at tricellular junctions, strengthening adhesion independently of Myosin-II contractility. Generalization to mammalian epithelia remains untested because the key experiment used Drosophila ovarian tissue, genetic activation, and modest sample sizes.

Confidence: high for the Drosophila follicular-epithelium finding; moderate for the narrower claim that physical E-cadherin nanoclustering is the direct causal event.