(A) Schematic views of in situ integrin ligand detection. Left, integrin αβ dimer on the cell surface; middle, αβ dimerized recombinant integrin ectodomain; right, in situ integrin ligand detection. (B) Comprehensive analyses of the ECM niche using E5.5 embryonic sections. Magenta, in situ binding of recombinant integrins; green, immunoreactivities for anti-laminin α1 (for integrins α3β1, α6β1, α6β4, α7x1β1, α7x2β1, α8β1, α10β1, α11β1, αVβ5, αVβ6, and αVβ8) and anti-laminin γ1 (for integrins α1β1, α2β1, α4β1, α5β1, α9β1, and αVβ3) mAbs; white, area double-positive for magenta and green signals; dotted lines, ExE basement membrane. The arrowheads indicate recombinant integrins bound to the ExE basement membrane. Bars, 50 μm.