The diverse morphologies of animal tissues are underlain by different 
configurations of adherent cells and extracellular matrix (ECM). Here, we 
elucidate a cross-scale mechanism for tissue assembly and ECM remodeling 
involving Cadherin 2, the ECM protein Fibronectin, and its receptor Integrin α5. 
Fluorescence cross-correlation spectroscopy within the zebrafish paraxial 
mesoderm mesenchyme reveals a physical association between Integrin α5 on 
adjacent cell membranes. This Integrin-Integrin complex correlates with 
conformationally inactive Integrin. Cadherin 2 stabilizes both the Integrin 
association and inactive Integrin conformation. Thus, Integrin repression within 
the adherent mesenchymal interior of the tissue biases Fibronectin 
fibrillogenesis to the tissue surface lacking cell-cell adhesions. Along nascent 
somite boundaries, Cadherin 2 levels decrease, becoming anti-correlated with 
levels of Integrin α5. Simultaneously, Integrin α5 clusters and adopts the 
active conformation and then commences ECM assembly. This cross-scale regulation 
of Integrin activation organizes a stereotypic pattern of ECM necessary for 
vertebrate body elongation and segmentation.