Mechanical heterogeneity along single cell-cell junctions is driven by lateral clustering of cadherins during vertebrate axis elongation

Morphogenesis is governed by the interplay of molecular signals and
mechanical forces across multiple length scales.  The last decade
has seen tremendous advances in our understanding of the dynamics of
protein localization and turnover at sub-cellular length scales, and at
the other end of the spectrum, of mechanics at tissue-level length
scales.  Integrating the two remains a challenge, however,
because we lack a detailed understanding of the subcellular patterns of
mechanical properties of cells within tissues.  Here, in the
context of the elongating body axis of Xenopus embryos, we combine tools
from cell biology and physics to demonstrate that individual cell-cell
junctions display finely-patterned local mechanical heterogeneity along
their length. We show that such local mechanical patterning is essential
for the cell movements of convergent extension and is imparted by locally
patterned clustering of a classical cadherin.  Finally, the
patterning of cadherins and thus local mechanics along cell-cell junctions
are controlled by Planar Cell Polarity signaling, a key genetic module for
CE that is mutated in diverse human birth defects.